Differential Diagnosis in Computed Tomography Sumeet Bhargava, Satish K Bhargava
INDEX
Page numbers followed by f refer to figure and t refer to table.
A
Abdomen 327
Abdominal lesions, common causes of 327t
Abdominal wall 331
anterior 332f
lesions 327, 328t
metastases 327f
Abscess 47, 205f, 215, 225, 228, 300, 352, 370, 534
amebic 340
hepatic 352f
cerebellar 140f
chronic 204
epidural 504f
formation 188f
large retroperitoneal 403f
loculated 224f
mediastinal 304
neck 504f
pancreatic 375
pelvic 436
periapical 496
periodontal 495
perirenal 426f
prostatic 438
psoas 404f
pyogenic 340
brain 93
renal 426, 426f
retropharyngeal 228f
soft tissue 518f
spinal
cord 111
epidural 123
Acavernous angioma 48f
Achalasia 294
Achondroplasia 127
Acoustic canal
internal 150t
stenosis, bilateral external 134f
Acoustic schwannoma 15f, 81, 150
Acquired cystic disease 420
Acquired immunodeficiency syndrome 27, 40, 102
Acquired toxoplasmosis 100
Actinomycosis 456
Adenocarcinoma 136, 262
Adenoid 206
cystic carcinoma 253
Adenoma 144, 263, 338
proximal tubular 422
Adenomatous hyperplasia 240, 247
Adenomatous polyp 379
Adhesive otitis media, chronic 140
Adnexa 442, 446
Adnexal lesions, common causes of 446t
Adnexal torsion 449
Adrenal adenoma 412, 412f
Adrenal carcinoma 412
Adrenal enlargement, causes of 411
Adrenal hyperplasia 413
Adrenal lesions 410
Adrenal paraganglioma 414
Adrenoleukodystrophy 22, 64, 98
Aeroceles 49
multiple 20f
Agger nasi cell 210, 213f
Air
bronchogram, differential diagnosis of 283
cells, opacification of 138
Alagille syndrome 155
Alexander's disease 21, 22, 25, 64, 96
Alexander's dysplasia 153
Allergic alveolitis, extrinsic 275
Allergic bronchopulmonary aspergillosis 280f
Allergic sinusitis 185
Altered globe size 163
Alveolar cell carcinoma 263, 284
Alzheimer's disease 77, 98, 104
Ameloblastoma 198, 457f
Aminoaciduria 21, 65
Amyloid angiopathy 74
Amyloidosis 237, 308, 358, 361
Anaplastic carcinoma 248
Anaplastic ependymoma 96
Aneurysm 17, 70, 71f, 82
malformation 3
Aneurysmal bone cyst 129, 199, 458, 458f
Angioblastoma 456
Angiofibroma 216
juvenile 206
Angioimmunoblastic lymphadenopathy 311
Angioma 7
Angiomyolipoma 422, 422f
Angiosarcoma 371
Ankle
and foot 529
joint effusion 483f
Ankylosis 512
Anomalies, duplication 430
Antral polyp, benign 192f
Antrochoanal polyp 189, 522
Antronasal fungal polyposis 200f
Aorta
aneurysm of 296
ascending 292
atherosclerosis of 409
Aortic aneurysm 301, 409
Aortic arch aneurysm 297f
Aortic dissection 409
Apical meningocele 152, 159
Aplasia 156
Apophyseal joints 515
Appendix, mucocele of 393, 394f
Arachnoiditis 121
Arch of atlas, anomalies of 500
Arch of axis, fracture of 538
Arnold-Chiari malformation 30, 36
Arterial infarct 37
right cerebral acute 38f
Arteriosclerosis 67
Arteriovenous malformation 27, 82, 87, 168, 258, 260, 427
Arthritis 505, 506f
mutilans 511
Articular disease, diagnosis of 526
Asbestosis 276, 319
Astrocytic hamartoma 164, 181
Astrocytoma 12, 54, 88, 96, 111
Ataxia-telangiectasia syndrome 77, 80
Atheroma 7
Atlantoaxial articulation 515
Atlantoaxial fusion malsegmentation 501
Atlantoaxial subluxation 501
Atlanto-occipital fusion 500
Atlanto-odontoid subluxation 537
Atlas assimilation 500
Atlas fracture 537
Atrophic fatty pancreas 374f
Atrophy 35
Auditory canal, internal 83
Autoimmune labyrinthitis 146
Axonal injury, diffuse 76, 78
B
Baker's cyst 513
Bamboo spine 514
Bartholin's cyst 441, 443
Basal cell carcinoma 136
Basal cisterns, effaced 78
Basal ganglia 8f, 51f
diffuse hypodensities 23
Basilar artery 56f
Bifid facial nerve 156
Bile pseudocyst 340
Biliary cystadenoma 339, 347
Biliary lesions 362, 364
common causes of 362t
Biliary pseudocyst 353
Biliary tract lesions 362
Biloma 340, 353
Bing-Siebenmann dysplasia 153
Binswanger's encephalopathy 104
Bladder 430
calculi 431
carcinoma 433, 433f
endometriosis 431
fungal ball in 432
intraluminal pseudomasses of 434
Blood dyscrasias 75
Bochdalek's hernia 298
Bone 454, 454t
adamantinoma of long 456
angiosarcoma of 459
avascular necrosis of 459
cyst, simple 487, 487f
destruction 184t, 199t
island 460
lesions, primary 194t
neoplasm
benign 453
malignant 453
resorption of 507, 508
sclerosis with periosteal reaction 455
small 508
temporal 132, 148t
tumors 456
salient features of 456
Bone-in-bone appearance 514
Bony labyrinthine anomalies 154t
Bony lesion 132, 132t, 452, 453, 524
spinal 499
Bony lytic metastases 63f
Bony texture, abnormal 195f
Bony type disease 133
Borrelia burgdorferi 103
Borreliosis 103
Bowel lesions, small 382, 383
Bowel loops, floating 402f
Bracket calcification 4f
Brain 1, 13t, 26, 69
abscess 101
causes of 18t
lesions 12, 37, 37t, 69
nontumoral 20
nodules, innumerable small enhancing 26
normal aging 104
occipital horns 35
parenchyma, parasagittal 25
pseudomasses of 18, 18t
tumors 74
causes of 17t
Brainstem
glioma of 55, 56f, 82, 84
hypodensity 23
lesions 76
Branchial cleft cyst
first 231, 251
second 218, 224, 228
Breast carcinoma 474f
Brodie abscess 455, 460
Bronchial atresia 313
Bronchiectasis 315
Bronchiolitis
acute 317
constrictive 316
obliterans 316
organizing pneumonia 318
obliterative 316
Bronchogenic carcinoma 264, 410f
Bronchus, carcinoma of 295
Buccal space 225
Budd-Chiari syndrome 342
Buphthalmos 175
Burkitt's lymphoma 497
Burst fracture
complete 536
incomplete 535
Buschke-Löwenstein tumor 395
Butterfly glioma 26
Button sequestrum 470, 492
C
Caffey's disease 455
Calcific pancreatitis, chronic 373f
Canavan disease 21, 22, 25, 64
Canavan-van Bogaert disease 97
Candida 249
Capillary angioma 47
Capillary hemangioma 169
Capsuloma 425
Carcinoma 365, 385
bronchus 296f
cecum 390f
Caroli disease 340, 351, 364
Carotid artery 217, 224
Carotid sheath mass 220f
Carotid space 219
Cartilage tumors 454
Castleman's disease 310, 406
Catscratch fever 249
Cavernous angioma 47, 70, 72
Cavernous hemangioma 168, 371
Cavitary prostatitis 437
Cavitating lesion 255
causes of 265t
Cavum septum pellucidum 17
Cavum velum interpositum 17
Cavum vergae 17
Cell carcinoma
large 262
small 262
transitional 424, 424f
Cellulitis 173
Cementoma 498
Central dot sign 351
Central nervous system 27
tumors 96f
Central pontine myelinolysis 105
Centrilobular emphysema 282
Cerebellar atrophy 77
Cerebellar hemisphere 43f, 77
Cerebellar vermis 77
Cerebellopontine
angle 83
masses, differential diagnosis of 81, 81t
left 15f
Cerebellum 82
astrocytoma of 84
Cerebral atrophy 77
Cerebral edema 78
diffuse 25
Cerebral hemisphere, left 70f
Cerebral infarction 92
Cerebral lesions, deep 76
Cerebral neuroblastoma, primary 90
Cerebritis 94
Cerebrospinal fluid 44f, 83, 182
Ceruminoma 136
Cervical
carcinoma 445
fascia 225
deep 229
space, posterior 228, 229t
thymic cyst 238
Cervix 441
Chance fracture 536
CHARGE syndrome 155
Chest 255
Chloroma 120
Cholangiocarcinoma 365
Cholangitis 364
Cholecystitis 365
acute 367f
Choledochal cyst 340, 364
large 365f
Choledocholithiasis 363f
Cholelithiasis 367
Cholesteatoma 134, 141, 141f
acquired 141
congenital 81, 142
primary 152
Cholesterol granuloma 17, 143, 151
Chondroblastoma 148, 152, 458, 461
Chondroma 198, 237
Chondromesenchymal hamartoma 203, 204f
Chondromyxoid fibroma 461
Chondrosarcoma 152, 199, 258, 461
Chordoma 7, 209, 464
Choriocarcinoma 292, 446
Choroid plexus
carcinoma 54, 85
papilloma 12, 53, 85, 96
Choroidal detachment 164, 178
Choroidal hemangioma 165, 180
Choroidal melanoma 165
Choroidal nevus 181
Choroidal osteoma 164, 181
Chronic injury 113
Cirrhosis 359
Cluster sign 353
Coal miner's pneumoconiosis 308
Coal workers’ pneumoconiosis 278, 321
Coalescent mastoiditis 141
Coats’ disease 164, 176
Cocaine 75
Coccidioidomycosis 270
Cochlea 146t
Cochlear aplasia 155
Cochlear hypoplasia 155
Cockayne syndrome 25
Codman's triangle 484
Codman's tumor 461
Cold abscess, calcified 484f
Colitis cystica profunda 390
Collagen diseases 508
Collagen vascular disease 279
Collapse
wafer-like 514
wedge-like 514
Coloboma 177
Colon mass, ascending 332f
Colonic lesions 389, 435
common causes of 389t
Colonic tuberculosis 399f
Colonic wall thickening, lesions with 389
Compression fracture 535
Concha bullosa 210, 211f
Congenital disorders 25
Constrictor muscles 215
Contour abnormalities 361
Cord contusion 113
Corduroy appearance 469
Corpus callosal agenesis 30
Corpus callosum 26
absence of 36f
agenesis 35
dysgenesis 30, 36
Cortical contusions 76, 77f
Cortical dermoid 464
Cranial fossa
bones of anterior 491f
lesions, middle 15
Craniopharyngioma 6, 12, 61, 62f, 92
Craniovertebral anomalies, differential diagnosis of 500
CREST syndrome 513
Crohn's colitis 392
Crohn's disease 383, 387, 387f
Cryptococcosis 42
Cumbo sign 260
Cyst 339, 507, 530
adrenal 411
apical 496
arachnoid 17, 45, 46f, 83, 120, 490
bony 225
bronchogenic 259, 264, 293, 296, 303f
choroid 181
fissure 45
plexus 45
colloid 49, 238, 239, 247
congenital 234, 235, 369
corpus luteal 447
dental 225, 496
dentigerous 496, 525
dermoid 171, 224, 490
developmental 496
duplication 383
ejaculatory duct 438
enteric 398
enterogenous 49
ependymal 45
epidermoid 120, 151, 152, 224, 465, 490
esophageal duplication 293
fissural 496, 525
follicular 447, 496
gastric duplication 377
hepatic 339, 349, 350f
leptomeningeal 17
lymphoepithelial 231
maxillary dentigerous 189
mediastinal 302
mesenteric 398, 398f
mesothelial 398
omental 398
pancreatic 374
parapelvic 418
parathyroid 242
pelvicalyceal 417
periodontal 496
peripelvic 418
pineal 17, 91
pleuropericardial 292
porencephalic 43, 44f
post-traumatic 271
primordial 496
prostatic 437
pyelogenic 417
radicular 496
residual 525
retention 222, 437, 522
sebaceous 17, 329
simple 417
springwater 292
subchondral 467
supratentorial
midline 17
paramidline 17
theca lutein 447
thymic 302
thyroglossal 224
duct 245
trichilemmal 17
unicameral 487
urachal 329
utricular 438
Cystadenocarcinoma 347, 450
Cystic bronchiectasis 282, 282f
Cystic glioma 55f
Cystic hygroma 223, 286, 293
Cystic lesions 184
multiple 449
Cystic lymphangioma, large 226f
Cystic pulmonary diseases 281, 281t
Cystic schwannoma 304
Cystic tumors 303
Cysticercosis 103
Cystitis
cystica 432
emphysematosa 432
Cytomegalovirus 2, 3, 9, 249
congenital 10f
D
Dacryoadenocystitis 175
Dandy-Walker
syndrome 30, 31f
De Quervain's thyroiditis 246
Degenerative disease 104, 124
Dehiscent jugular bulb 158
Dementia, subcortical 77
Demyelinating disease 20, 22, 22t, 29
Demyelinating disorders, congenital 96
Demyelinating lesion, causes of 21t
Dens fracture 538
Dermal sinus, dorsal 114
Desmoplastic fibroma 464
Desquamative interstitial pneumonia 278
Destructive lesions 493
Diaphragmatic hernia 302, 267f
Diaphyseal achalasia 477
progressive 149
Diastematomyelia 109, 110f
Diastrophic dysplasia 126, 127
Diffuse hepatic lesions, differential diagnosis of 359, 359t
Diffuse liver diseases, common causes of 355t
Discal calcification 501
Discal disease 122
Disk herniation, postoperative 126
Double-target sign 353
Down syndrome 25, 501, 515
Dromedary hump 421
Drug abuse 75
Duodenal diverticulum 384f
Duodenum 382f
adenocarcinoma of 385f
Dwarf cochlea 156
Dyke-Davidoff-Masson syndrome 77, 79
Dysplasia
epiphysealis hemimelica 509
multiple 154f
E
Ear 132
lesions, differential diagnosis of 132
Echinococcal cyst 339, 370
Eclampsia 75
Ectatic carotid artery 220
Ectopic pancreas 380
Edema, nonenhancing 38f
Effusion 151
Eggshell calcification 307
Elbow
and wrist 530
tubercular osteomyelitis of 483f
Emboli 270
Embryonal cell carcinoma 292
Embryonal rhabdomyosarcoma 144
Emphysema 315
Emphysematous cholecystitis 365
Empyema 49
Encephalitis, acute disseminated 68, 105
Encephalocele 208
Encephalomalacia 43
Encephalomeningocele 204
Enchondroma 464
Endocrine neoplasia, multiple 248
Endodermal sinus tumor 292
Endolymphatic sac
lesions 146
tumors 146
Endometrioma 448
Endometriosis 328
Endophthalmitis 165, 177
Endosteal hyperostosis 148
Engelmann-Camurati disease 489
Eosinophilic gastritis 380
Eosinophilic granuloma 144, 146, 197, 470
Ependymal enhancement, causes of 27t
Ependymoma 57, 84, 89, 96, 111, 119
Epidural lesions 16
Epidural lipomatosis 120
Epiphrenic esophageal diverticulum 295
Esophageal masses 296
Esophagus, distal carcinoma of 297f
Esthesioneuroblastoma 187f, 202
Etate crible 22
Ethmoid bulla 210, 212f
Ethmoid infundibulum 212f
Ethmoid mucocele 190f
Ethmoid sinus, left 190f
Ethmoid sinusitis 188f
Ewing's sarcoma 199, 465, 466f, 474
Exostoses 137
Expansile bony lesions, common causes of 453t
External ear 132t, 154f
lesions 132t
Extramedullary hematopoiesis 299
Extraparotid lesion 231
Extrapyramidal disorders 77
Eye, thickened coats of 165t
F
Facial nerve
anomalies 156t
anterior migration of 157
duplication of 156
hypoplasia, congenital 156
neuroma of 144
schwannoma 150
Fahr's disease 3f, 25, 80
Fahr's syndrome 2
Falcine lesions 16
Fallen fragment sign 487
Fatty infiltration, diffuse 356, 357f
Feeding vessel sign 258
Femur, distal 472
Fetal lobulations 421
Fibrin balls 323
Fibrinoid leukodystrophy 96
Fibroid 445f
Fibrolamellar hepatocellular carcinoma 337, 344, 345f
Fibrolipomatosis 416
Fibromatosis 532
Fibrosarcoma 466
Fibrosing alveolitis 274
Fibrosing mediastinitis 314f
Fibrosing mesenteritis, chronic 399
Fibrosis, retroperitoneal 408
Fibrous cortical defect 466
Fibrous dysplasia 137, 148, 194, 195f, 458, 467, 491f
Fibrous histiocytoma, malignant 473, 533
Fibrous tissue tumors 454
Fibrous tumor, malignant 325
Fibrous type disease 133
Filum terminale 116
Fistula 436
Flexion distraction 536
Fluid lesions 184
Focal bacterial nephritis, acute 426
Focal basal ganglia, bilateral 23
Focal caliectasis 417
Focal fatty infiltration 341, 355
Focal hepatic lesions 335
common causes of 335t
Focal hepatic metastasis 346f
Focal interhemispheric blood 71
Focal lesions 488
Focal nodular hyperplasia 338, 349
Foley's bulb 434
Follicular carcinoma 248
Foramen magnum 15
Foreign body 164, 318
Fracture 521
Frontal horns, abnormal 30
Frontal sinus 185f
extension 210
mucocele of 190f
Frontoethmoidal encephalocele 209f
Fucosidosis 65
Fungal infection 192f, 310
Fungal sinusitis 199, 200f, 522
Fungiform papilloma 191
G
Gallbladder 362
carcinoma 365
fundus of 366f
Gangliocytoma 89
Ganglioglioma 58, 89
Ganglioneuroma 89
Gardner's syndrome 479
Garre's osteomyelitis 455, 467
Gartner's duct cyst 441, 442
Gastric adenocarcinoma 379f
Gastric bezoar 382
Gastric carcinoma 378
Gastric diverticulum 378
Gastric lesions 377, 377t
Gastric varices 377, 381
Gastroesophageal junction mass 378f
Gastrointestinal lesions 377
Gastrointestinal tumors 473
Genioglossus muscle 221
Geniohyoid muscle 221
Genitourinary lesions 414
Germ cell tumor 59, 258, 287, 292
Germinoma 12, 59, 91, 447f
Gerota's fascia 426
Giant apical air cell 159
Giant cell
astrocytoma, subependymal 55, 56f
tumor 137, 198, 458, 468
Giant hypertrophic gastritis 381
Giant osteoid osteoma 475
Giant periapical granuloma 495f
Glioblastoma multiforme 26, 88
Glioma 6, 96
Gliomatosis cerebri 55
Gliosis 87
Glomus jugulare tumor 82, 145, 145f, 493
Glomus tumor 220, 469
Glomus tympanicum 144
Glycogen storage disease 21, 65, 355
Gorlin syndrome 496
Gorlin-Goltz syndrome 52
Granulocytic sarcoma 120
Granuloma, infectious 255
Granulomatous disease 307
Granulomatous masses 186f
Granulomatous sialadenitis 249
Granulomatous thyroiditis, subacute 246
Graves’ disease 174, 245
Gray matter lesions 21
Gut wall signature 383
Gyriform enhancement 26
H
Haller cell 210, 213f
Hallervorden-Spatz disease 25, 100
Hamartoma 263
Hand-Schüller-Christian disease 470, 471
Hashimoto's thyroiditis 245
Hearing loss, X-linked congenital mixed 156
Hemangioblastoma 39, 85, 90, 112
Hemangioma 83, 135, 135f, 226, 231, 237, 251, 338, 347, 469, 531
Hemangiopericytoma 58, 58f
Hematoma 42, 71f, 204, 206, 263, 328, 534
epidural 94
hypertensive acute 70f
intramural 388
bladder 434
subcapsular 341, 354
Hemivertebra 126, 128
Hemochromatosis 356, 360
Hemophilic pseudotumor 470
Hemorrhage 69, 74, 75, 87, 164, 521
acute 69
adrenal 411
benign 74
chronic 69
idiopathic pulmonary 279
intracerebral 94
intraparenchymal 72
malignant 74
perinatal 69, 72
sinus 193
subacute 69
subarachnoid 25, 70, 72, 78
tumoral 70
Hemorrhagic contusion, coincidental small 24f
Hemorrhagic cystitis 432
Hemorrhagic infarction 69, 73
Hemorrhagic ovarian mass 450f
Hepatic abscess, large 352f
Hepatic adenoma 349
Hepatic adenomatosis 338
Hepatic disease, diffuse 356f
Hepatic flexure 399f
Hepatic hemangioma, typical 348f
Hepatic infarct 355
Hepatic laceration, large 354f
Hepatic lesions 335
differential diagnosis of 337
Hepatic lobe herniation, left 267f
Hepatic metastases 408f
Hepatic parenchyma 353, 356, 358
Hepatic tumors, common causes of 337t
Hepatic venous occlusion 342
Hepatobiliary lesions 335
Hepatoblastoma 347, 348f
Hepatocellular carcinoma 337, 344
diffuse 358, 361
Hepatocellular disease 75
Hepatolenticular degeneration 99
Hernia 331
femoral 333
obturator 333
traumatic ventral 332f
types of 331, 331t
Herpes encephalitis 100
Heterotopias 36
Hiatus hernia 294, 295, 301
Hiatus semilunaris 212f
Hilar lip 421
Hip, tuberculosis of 484f
Histiocytosis 281, 470
Hodgkin's disease 303, 325, 514
Holoprosencephaly 30, 33
Homocysteinuria 99
Huntington's disease 25, 79
Hyaloid detachment, posterior 164, 178
Hydatid cyst 45, 93, 260, 260f, 351
healing 351f
Hydatid disease 264, 471
Hydranencephaly 35
Hydrocephalus 32, 78
Hydrometra 444
Hydromyelia 110
Hydroxyapatite deposition disease 128
Hypercementosis 498
Hyperdense basal ganglia, bilateral 25
Hyperdense bile 362
Hyperdense brain lesions, causes of 24t
Hyperdense cisterns 78
Hyperdense falx 25
Hyperdense renal lesion 415
Hyperdense skull base 490
Hyperdense vitreous, common causes of 164t
Hyperperfusive hepatic abnormalities, common causes of 343t
Hyperplastic gastropathy 381
Hyperplastic polyp 379
Hypertension, portal 362f, 372f
Hypertrophied column of Bertini 421
Hypochondroplasia 127
Hypodense bony lesions, common causes of 453t
Hypodense lesion, causes of 20t, 27t
Hypopharynx 215
Hypophysitis 187f
Hypoplastic dens 501
Hypoplastic left lamina 110f
Hypoproteinemia 383, 388
Hypothalamic glioma 12
Hypoxic ischemic encephalopathy 67
Hyrtl's fissure 159
I
Idiopathic pulmonary fibrosis 274, 281
Idiopathic skeletal hyperostosis, diffuse 501
Ilium, osteomyelitis of 481f
Ill-defined lytic lesions 453
common causes of 453t
Infarct, chronic 42
Infection 100
disseminated 26
orbital 173
suppurative 146
Infectious lesions 74
Inflammations 100
Inflammatory disease 74, 431
Inflammatory lesions 83
Inflammatory lymph nodes 290
Inflammatory polyp 379, 522
Infraorbital nerve and canal 211
Infratentorial lesions, differential diagnosis of 84, 84t
Inguinal hernia 334
Inherited disorders 25
Inner ear 148t, 150t, 154f
cavity of 155
dysplasia, congenital malformations of 153t
Interclinoid ligaments 5
Internal ear lesions 146
Interstitial disease 272f
Interstitial lung disease 272, 272f
common causes of 273t
Interstitial pneumonia, nonspecific 278
Intervertebral foramina, enlarged 502
Intra-articular loose bodies, differential diagnosis of 515
Intracerebral hemorrhage, hypertensive 70
Intraconal lesions 165t
Intracranial calcification 1, 4f, 5t, 12f
causes of 1t, 3f
Intracranial lipoma 4f
Intracranial masses 19, 19t
Intracranial pressure, elevated 167
Intradural lipoma 117
Intrahepatic hematoma 341, 353f, 354, 354f
Intraosseous ganglion 471
Intraparenchymal hemorrhagic lesions 69
Intraparotid lesion 229
Ischemia 388
Ischemic encephalopathy 25
Ivory vertebra 486
J
Jaccoud's arthritis 507
Jaw 494
ameloblastoma of 497
lesion 489
salient features of 495
sclerotic lesions of 495
Joint
diseases, differential diagnosis of 526, 526t
effusion 506, 506f
space narrowing 507
Jugular diverticulum 158
Jugular foramen agenesis 158
Jugular vein 217
internal 224
Juxtacortical chondroma 486
K
Kartagener's syndrome 522
Keratocyst 525
Keratosis obturans disease 133
Key-hole appearance 30
Kidney, right 419f
Klippel-Feil syndrome 126, 127
Knee 528
right 460f
Koehler's disease 509
Krabbe's disease 21, 22, 63, 97
L
Labyrinthine aplasia, complete 155
Laceration 341
Lacrimal gland
lesions, malignant 164
tumor 173
Lamellar concha 210, 211f
Lamina papyracea 212f
Langerhans cell histiocytosis 91, 276
Laryngeal space, causes of 234t
Laryngocele 236
Left orbit, coronal anatomy of 161f
Leigh disease 25, 66, 99
Leiomyoma 296, 379, 384
Leiomyosarcoma 296, 380, 384
Leptomeningeal carcinomatosis 113
Lesion 238, 264
benign 255, 256t
causes of enhancing 27t
congenital 312
developmental 255
dural 16
enhancing 24
malignant 255, 256t
miscellaneous 138
nonenhancing 24
of spleen, common causes of 368t
of vertebra, causes of expansile 499t
orbital 161, 164
peripheral 263
cavitating 268f
retroperitoneal 403
tumor-like 29, 456
vascular 17, 255
ventricular 29
Letterer-Siwe disease 470, 471
Leucinosis 99
Leukemia 51, 286, 372, 425, 471
acute 472
chronic 472
Leukodystrophy disease 22t
Leukoencephalopathy 12f
Ligament 129
Ligamentum flavum
hypertrophy 124, 130f
ossification of 129
Lingual thyroid 233
Lipoblastoma 302
Lipoma 7, 12, 38, 86, 92, 218, 219f, 301, 329, 339, 380, 387, 392, 397, 472, 531
chordoma 83
Lipomatosis 301
Lipomyelomeningocele 116
Liposarcoma 397, 532
Lissencephaly 9
Liver 351f, 357f, 358f
causes of 361t
cirrhosis of 344f
disease, diffuse 355
fatty 360
infarction 342
infiltrating mass in 357f
Lobar nephronia 426
Lobe
right 352f
frontal 72f
temporal 51f
Local pleural masses 321
Lowe's syndrome 163
Lucent bone lesions 454, 454t
Ludwig's angina 222
Lumbar hernia 331
Lung
adenocarcinoma of 263f
right 261f
tissue, normal 255
zones in 259t
Lyme disease 101, 103
Lymph nodes 215, 242
calcified 307
enhancing 310
hypodense 308
Lymphadenopathy 243
Lymphangiectasia 429
Lymphangioma 168, 215, 225, 231, 251, 286, 371, 398, 531
Lymphangiomatosis 429
Lymphangitis carcinomatosa 274
Lymphectasia, retroperitoneal 404f
Lymphocele 429
Lymphocytic interstitial pneumonitis 281
Lymphocytic thyroiditis, chronic 245
Lymphoma 50, 86, 90, 146, 171, 202, 207, 217, 254, 269, 284, 285f, 286, 309, 372, 376, 380, 386, 425, 523
diffuse 359, 361
of bone, primary 487
Lymphomatous adenopathy 405f
Lymphosarcoma 284
Lytic lesion 453, 456, 488, 490, 492494
common causes of 452t, 456t, 491t
of jaw, common causes of 494t
of orbit, common causes of 493t
of rib, common causes of 488t
well-defined 452
M
Macrocystic tumor 376
Macrophthalmia 164, 175
Macular degeneration 165, 181
Madelung's deformity 477
Madura foot 472
Maduramycosis 472
Maffucci syndrome 465
Malakoplakia 432
Maple syrup urine disease 99
Marchiafava-Bignami disease 105
Massive fibrosis, progressive 259, 283
Masticator space 225
causes of 225t
Mastoid lesions, causes of 138t
Maxilla
carcinoma of 203f
osteomyelitis of 480f
Maxillary dentoalveolus 211
Maxillary ostium 212, 212f
Meatus, middle 211
Mediastinal lymphadenopathy 307, 307t
Mediastinal masses 285, 301
anterior 286, 286t, 290t
middle 293
posterior 298
Medullary carcinoma 248
Medullary cystic disease 420
Medulloblastoma 52, 84, 96
Medulloepithelioma 181
Melanocarcinoma 74
Melanoma, malignant 136
MELAS/MERRF syndrome 66
Ménétrier's disease 377, 381
Meningioma 6, 12, 52, 81, 85, 89, 96, 117, 150, 164
Meningitis 101, 159t
Meningocele 204, 208, 304, 490
dorsal 114
Meningoencephalocele 490
Mesenchymal bladder tumors 432
Mesenchymal hamartoma 339, 349
Mesenchymal tumors, retroperitoneal 406
Mesenteric fat stranding 400f
Mesenteric lesion 396, 396t
Mesenteric mass, large 396f
Mesenteric panniculitis 399
Mesoblastic nephroma 425
Mesothelioma 324, 401
Metabolic disorders, congenital 99
Metachromatic leukodystrophy 22, 25, 63, 98
Metastases 62, 83, 86, 91, 104, 124, 129, 137, 146, 167, 203, 241, 248, 254, 265, 307, 337, 345, 473, 524
types of 346t
Metastatic disease 358f
diffuse 358, 361
Metastatic lesions 474
Metastatic lymphadenopathy, bilateral 244f
Metastatic tumor 451
Methyl alcohol 25
Methylmalonic aciduria 25, 98
Michel deformity 155
Michel dysplasia 153
Microcystic tumor 376
Microphthalmia 163, 175
Midbrain 34
Middle ear 138, 154f, 493
causes of 138t
lesion of 138
Mitochondrial encephalopathy 25
Mondini's dysplasia 153, 155
Morgagni hernia 286, 292
Morquio syndrome 501
Moth-eaten lesions 454, 454t
Mucinous 450
adenocarcinoma 258
Mucocele 189, 522
carotid artery aneurysm 152
Mucoepidermoid carcinoma 253
Mucolipidosis 65
Mucopolysaccharidoses 65
Mucosal disease 392
Mucus retention cyst 189, 204
Müllerian duct cyst 438
Multicentric central nervous system lesion 29
Multicystic dysplastic kidney 419
Multifocal brain tumors 29
Multifocal infarction, subacute 26
Multifocal leukoencephalopathy, progressive 3
Multifocal white matter lesions 22
Multilocular cystic nephroma 416, 419
Multilocular nephroma 419f
Multilocular thymic cysts 303
Multinodular goiter 291f
Multiple vertebra, causes of 499t
Mumps 249
Mural hematoma 383
Musculoskeletal system 452
Myelinating lesion, causes of 21t
Myeloblastic leukemia, acute 51
Myeloblastoma 120
Myelocele 109
Myelocystocele 109
Myelolipoma 413
Myeloma, multiple 474
Myelomeningocele 109
Myelopathy, acute transverse 110
N
Nabothian cyst 444
Nasal cavity
left 186f
right 187f
Nasal septum, destruction of 186f
Nasal sinus lesions 183, 183t
Nasopharyngeal angiofibroma 207f
Nasopharyngeal carcinoma 205
Nasopharyngeal lesions
causes of 204t
common 205t
Nasopharyngeal mass 216f
Nasopharynx 215
Neck 215, 242
space lesions 220
Neoplasm 107
benign 255
Neoplastic disease 104, 271
Nephroblastoma 425
Nephroblastomatosis 421
Nephronophthisis 420
Nerve sheath tumors 163, 219
Neural tumors 60
Neuroblastoma 413, 474
Neurocutaneous syndrome 22
Neurocysticercus 40
Neurofibroma 118, 218, 532
dumbbell-shaped 119f
Neurofibromatosis 9, 22, 164, 165f
Neurogenic masses 298
Neurogenic tumor 193, 299, 387, 407
Neurolemoma 532
Nodes, calcification in 245
Nodular compensatory hypertrophy 421
Nodular pleura 326f
Nodular regenerative hyperplasia 339
Nonacoustic schwannoma 82
Nonenhancing lesion, causes of 20t
Nonhemorrhagic contusion 21f, 37
Non-Hodgkin's disease 325
Noniatrogenic coagulopathy, causes of 75
Noninfectious disorders 280
Noninfectious granuloma 255
Nonodontogenic lesions 494
Nonossifying fibroma 475
Nonsteroidal anti-inflammatory drugs 478
Norrie's disease 163, 164, 176
Nose 204f
O
Obstructive pulmonary disease, chronic 318
Occipital bone, anomalies of 500
Occipital condylar hypoplasia 500
Occipital lobes 34
Occipital vertebra 500
Occult intrasacral meningocele 114
Ocular metastasis 165, 179
Odontogenic lesions 494
Odontoid bone 501
Odontoma 197, 525
Olfactory fossa depth 210
Oligodendroglioma 26, 56, 89
Olivopontocerebellar atrophy 80
Olivopontocerebellar degeneration 77
Omental lesion 396
common causes of 396t
Oncocytoma 422
Onion peel sign 260
Onodi cell 210
right sided 214f
Opacification, common causes of 184t
Ophthalmic vein thrombosis, superior 175
Optic disc
drusen 182f
ocular hemorrhage of 182
Optic glioma 12
Optic nerve
glioma 165, 166f
left 166f
meningioma 166f
right 214f
tumor 164
variations 210
Optic neuritis 167
Optic perineuritis 167
Oral cavity 215
causes of 232t
lesions of 232, 232t
Oral mucosa 221
Orbital lesions 493
causes of 161, 162t
Ormond's disease 408
Ornithine transcarbamylase deficiency 98
Oropharynx 215
Os odontoideum 126, 128
Osseous destruction 132
Osseous involvement 132
Ossification center, changes in 508
Ossifying fibroma 148, 194, 196f, 525
Osteitis condensans ilii 527
Osteitis deformans 130
Osteoarthritis 509f
Osteoblastoma 130, 458, 475
Osteochondroma 130, 131f, 476, 477f
Osteoclastoma 468, 468f
Osteogenesis imperfecta 147
Osteoid
neoplasms 454
osteoma 478, 478f
Osteolytic metastasis 492f
Osteoma 137, 196, 197f, 479
frontal 185f
Osteomeatal complex frontoethmoid recess 212f
Osteomyelitis 479
actinomycotic 188f
acute 479
chronic 480, 481f
subacute 480
tubercular 482, 482f
Osteopenia 506, 514
diffuse 472
Osteophytes 509
Osteosarcoma 199, 258, 458, 484, 485f
Osteosclerosis 488, 514
benign 498
Otitis externa, malignant 135, 136f
Otitis media
chronic 141f
granulomatous 140
suppurative 139f, 140, 140f
with mastoiditis 138
Otosclerosis 146
Otosyphilis 146
Ovarian cyst, simple 447
Ovarian cystadenoma 450
Ovarian dermoid 449, 449f
Ovary, hemorrhagic lesions of 447
P
Pacchionian bodies 5
Paget's disease 130, 147, 149, 196, 458, 466, 468, 486, 488, 514
Pancreas
atrophic 373
fatty 373
Pancreatic adenocarcinoma 375
Pancreatic atrophy, mild 373f
Pancreatic islet cell tumor 376
Pancreatic lesion 368, 372, 372t
hypervascular 373
Pancreatic pseudocyst 370, 374
Pancreatitis, acute 375f, 397f
Panencephalitis, subacute sclerosing 68, 105
Papillary carcinoma 247
Papillary cystadenoma lymphomatosum 232
Papilloma 237, 523
inverted 186f, 201
Papillomatosis 237
Paradoxical middle turbinate 210
Paraganglioma 82, 119, 220
Paragonimiasis 270
Paralaryngeal space, right 236f
Paranasal sinus
anatomical variants of 210, 210t
carcinoma 202
development of 209, 209t
lesions 183
Paraovarian cysts, congenital 447
Parapelvic lymphangiectasia 418
Parapharyngeal lesion 215, 215t
Parapharyngeal space 217
Paraseptal emphysema 282
Parathyroid gland lesions 238, 238t
Parathyroid lesion 239t, 242
Parathyroid mass 242
Parenchymal cell tumors 59
Parietal bone, right 476f
Parietal lobe, right 24f
Parkinson disease 25
Parosteal osteosarcoma 485
Parotid gland 230f
accessory 226
right 232f
Parotid lesions 229
differential diagnosis of 249, 249t
space 229
Parotid space, causes of 230t
Parotitis, acute 249
Pars flaccida 142
Pars tensa 142
Pelizaeus-Merzbacher disease 21, 22, 64, 97
Pelvic
carcinomatosis 435
edema 435
fibrosis 435
hematoma 436
lesions 430, 434
lipomatosis 435
lymphocele 436
trauma 527
urinoma 436
Pencil-in-cup appearance 508
Periapical granuloma 496
Pericardial fat pad 292
Perilesional edema 28f
Perinephric lesions 427
common causes of 427t
Periosteal new bone formation 510
Periosteal osteosarcoma 485
Periportal edema 354
Perirenal pseudocyst 428
Perisylvian region, right 57f
Peritoneal carcinomatosis 401
Peritoneal dissemination and adenopathy 451f
Peritoneal lesion 396, 396t
Peritoneal metastases 402f
Persistent hyperplastic primary vitreous 176
Persistent stapedial artery 158
Petroclinoid ligaments 5
Petrositis, acute 151
Petrous apex lesion, common lesion of 151t
Petrous apicitis 153
Petrous bone, malformations of 159t
Petrous pyramid 493
Pharyngeal lesion 215
causes of 215t
Pharyngeal mucosal space 215
Phenylketonuria 65
Pheochromocytoma 414
Phleboliths 237
Phthisis bulbi 163
Pick's disease 77, 79, 98
Pilocytic astrocytoma 96
Pineal cell tumors 59
Pineal gland 5, 59f
Pinealoblastoma 96
Pineoblastoma 12, 59
Pineocytoma 59
Pituitary adenoma 12, 60
Pituitary gland 5
Pituitary macroadenoma 61f
Plasmacytoma 198, 486
Pleomorphic adenoma 252
malignant 230f
Pleura 325
mesothelioma of 324f
Pleural calcification 318
causes of 318t
Pleural effusion, loculated 322f
Pleural lesions 318
Pleural lipoma 323
Pleural lymphoma 325
Pleural thickening 326
Pleuropulmonary blastoma 264
Plexiform neurofibroma 165f
Pneumatosis cystoides coli 391
Pneumocystis carinii
infection 307
pneumonia 271, 278
Pneumonia 264
cryptogenic organizing 317
Pneumonitis, hypersensitivity 275
Polka dot appearance 469
Polycystic kidney disease 418
Polycystic liver disease 350f
Polymicrogyria 36
Polyp 208, 237, 385
regenerative 379
Portal vein thrombosis 359
acute 357
Postinflammatory sclerosing osteitis 498
Poststyloid compartment 219
causes of 218t
Pott's disease 502, 515
Pott's spine 504f
type of 503f
Pouch of Douglas 402f
Prestyloid compartment, causes of 217t
Propionic acidemia 98
Proptosis, left-sided 190f
Prostate
benign hyperplasia of 439f
carcinoma 439
Prostatic calculi 440
Prostatic hyperplasia, benign 439
Prostatic lesions 437, 437t
Protruding jugular bulb 158
Prussak's space 142
Pseudocyst, post-traumatic 369
Pseudomembranous colitis 394
Pseudomyxoma peritonei 395f, 399
Pseudotumor 169
Psoriatic arthritis 510
Pulmonary artery
left 261f
right 296f
Pulmonary edema 274
Pulmonary infarction 260
Pulmonary lesions 285f
Pulmonary metastases 265f
contralateral 324f
multiple 266f
Pulmonary nodular lesion 255
Pulmonary sequestration 259
Pulmonary varix 260
Pulmonary vessels, visualization of 283
Pyogenic arthritis 516, 516t
Pyogenic spondylitis 504
Pyometra 444
Pyriform fossa, left 235f
R
Rachischisis
anterior 500
posterior 500
Racing car sign 35
Radiation injury 342
Radiation myelopathy 110
Radiation necrosis 92
Radiation pneumonitis 283
Ranula 222
Rathke's cleft cyst 17, 49
Rectal duplication 389f
Rectal lesion 435
Rectosigmoid carcinoma 391f
Regional intrathoracic lymph nodes, classification of 304, 305t
Reiter's syndrome 507, 510, 514, 515
Renal cell carcinoma 423, 423f
Renal cyst, calcification in 415f
Renal hamartoma 422
Renal leiomyoma 425
Renal lesions 414, 416
bilateral 415
common causes of 414t
Renal lymphangiectasia, bilateral 429f
Renal pelvis, right 424f
Renal pseudotumor 421
Renal sinus
cyst 418
lipomatosis 416
Reproductive system lesions
female 441
male 437
Respiratory tract infection, upper 241, 248
Reticulum cell sarcoma 487
Retinal angioma 181
Retinal astrocytoma 164, 181
Retinal detachment 164, 178
Retinal dysplasia 176
Retinal telangiectasia, congenital 176
Retinoblastoma 164, 178, 182
Retractile mesenteritis 399, 400f
Retrobulbar soft tissues 186f
Retrolental fibroplasia 163, 177
Retrolental hyperplasia 164
Retromandibular vein 229
Retroperitoneal fibrosis, malignant 408f
Retroperitoneal liposarcoma, large 407f
Retroperitoneal mass lesion 407f
Retroperitoneal sarcoma, large 406f
Retropharyngeal space 227, 227t
Retrosternal goiter 290
Rhabdomyosarcoma 164, 171, 204, 208, 264, 533
Rheumatoid arthritis 237
Rhinocerebral mucormycosis 208
Rib
chondrosarcoma of 462f
lesions 488
multiple 489
Riedel's thyroiditis 246
Ring enhancing lesions 26
pneumonic for 26
Rosai-Dorfman disease 16
Rotatory atlantoaxial dislocation 537
Rugger Jersey spine 514
Ruptured aneurysms 70
S
Sacral meningocele, anterior 114
Sacroiliac joint 526
Salivary gland adenoma 218
Salivary inclusion defect 498
Salpingopharyngeus muscle 215
Sarcoidosis 146, 174, 275, 275f, 358, 360, 371
Scalp, lipoma of 519f
Scar, postoperative 125
Scheibe dysplasia 153
Schilder's disease 105
Schistosoma japonicum 360
Schistosomiasis 360
Schizencephaly, bilateral 44f
Schizophrenia 98
Schmorl's nodes 514
Schwannoma 85, 118, 169, 302, 395
malignant 227
Sciatic hernia 334
Scleritis 165, 177
Sclerosing endophthalmitis 177
Sclerosis, multiple 66, 87, 105
Sclerostenosis 148
Sclerotic bone
disease 455
lesions, common causes of 455t
Sclerotic lesions 456, 488, 493
common 148t
causes of 456t, 489, 493t
Seminal vesicle
cyst 440
lesions 440
neoplasms 440
Seminoma 292
Seroma 406
Serous 450
Sheath meningioma 166
Shepherd's crook deformity 467
Short pedicles, congenital 126
Shoulder 530
joint 509f
Sialadenitis, chronic recurrent 249
Sialosis 250
Sickle cell disease 480, 514
Sigmoid adenocarcinoma 391f
Silicosis 277, 307
Sinonasal cavity
causes of 199t
lesions of 199t
mass lesions of 184t
Sinonasal polyposis 191, 192f
Sinus
ethmoid 209
frontal 209
inner table of frontal 185f
maxillary 209, 212
right frontal 197f
sphenoid 209
straight 33
Sinusitis 521
acute 184
chronic 185
Sjögren syndrome 250
Skull base
common causes of 490t
hyperdense lesions of 490t
Skull lesion 489
Skull vault 489t, 490, 491t
sclerotic lesions of 489
Small bowel lesions, common causes of 382t
Soap bubble appearance 468, 497
Soft tissue 174f
atrophy 513
calcification 513, 516
causes of 132t
density 164
extension 203f
swelling 512
Soft tissue lesions 132, 138, 205f, 228f, 257f, 521t
common causes of 517t
differential diagnosis of 521, 530, 530t
Soft tissue mass 131f, 519f
benign 532
common 150t
extradural 63f
lesion 433f
large 186f, 466f
Soft tissue sarcoma
large 518f
malignant 533
Solitary dense pedicle 502
Solitary pulmonary nodule 255, 258, 259, 262
classification of 259t
Solitary sclerotic bone lesion 455
Space occupying lesions, causes of 13t
Sphenoid bone 195f
osteomyelitis of 187f
Spiculated sunray appearance 497
Spigelian hernia 331
Spina ventosa 483
Spinal accessory 243
Spinal arteriovenous malformation 122
Spinal canal stenosis 130f
Spinal cord 106
lesions 106, 107
causes of 107t
common 109t
Spinal fractures, differential diagnosis of 535, 535t
Spinal hematoma 121
Spinal stenosis 126t, 127t
lesions with 126
Spine 513
Spleen
abscess in 370f
diffusely hyperdense 368
tuberculosis of 369f
Splenic hematoma, large 369f
Splenic infarct 371, 372f
Splenic lesion 368
Splenic pseudocyst 375f
Splenosis 401
Split cord 109
Spondylitis 123
Spondylodiscitis 123
Spondylolisthesis 124
Spongiform leukodystrophy 97
Squamous cell carcinoma 135, 143, 216, 262, 269f, 271, 523
Stafne's mandibular defect 498
Staphylococcus 249
Stein-Leventhal syndrome 448
Stewart's granuloma 201
Stomach, diffuse lymphoma of 381f
Streptococcus 249
Sturge-Weber syndrome 2, 9, 11f
Subchondral sclerosis 509, 510f
Subcutaneous edema 408f
Subcutaneous fat, edema in 517f
Subdural hematoma 7, 32, 72, 95
acute 24f, 32f
Subdural lesions 16
Subependymoma 57
Subfalcine 30
herniation 32f
Sublingual gland, mucocele of right 222f
Sublingual space 220
causes of 221t
Submandibular gland, sialadenitis of 223f
Submandibular space 223
causes of 223t
Subpleural honeycomb cysts 272f
Subtalar osteoarthritis 510f
Suprasellar cystic mass lesion 62f
Supratentorial mass lesions, differential diagnosis of 88, 88t
Swan-neck deformity 511
Swirl sign 69
Sylvian fissure 33
Synovial sarcoma 258, 533
Systemic lupus erythematosus 273, 507
Systemic sclerosis 279f
T
Tail sign 222
Talus, tubercular osteomyelitis of 483f
Tarsal coalition 529
Tay-Sachs disease 65
Tegmen tympani, dehiscence of 159
Temporal lobe
left 8f
right 51f
Temporomandibular joint 530
Tentorial meningioma 53f
Teratocarcinoma 287
Teratoma 12, 59, 91, 290, 380
benign 287
malignant 287
Testes 441
ectopic 441
undescended 408, 441
Tethered cord 115
Thigh, intramuscular lipoma of 520f
Thoracic meningocele, lateral 300
Thornwaldt's cyst 204, 215, 216
Thymic mass, large 291f
Thymolipoma 302
Thymoma 288, 290, 291f
Thymus, normal 286
Thyroid
adenoma 240, 247
carcinoma 240, 258
diseases, differential diagnosis of 245
gland lesions 238
causes of 238t
goiter 246
granuloma 239
large carcinoma of 241f
lesion 239t
differential diagnosis of 245t
lymphoma 241, 248
ophthalmopathy 174
stimulating hormone 248
Thyroiditis 239
acute suppurative 246
Tibia
metaphysis of right 460f
upper end of 468f, 485f
Tick borne multisystem disease 103
Tight filum terminale 115
Tissue, granulation 143
Tongue 221f
Tooth appearance, floating 497
Tooth-bearing area 211
Toxic
causes 25
demyelination 67
encephalopathy 25
Toxocariasis 164
Toxoplasmosis 40
congenital 8f
Tracheal bronchus 313
Tracheal stenosis 312, 314
Tracheobronchial tree, lesions of 312
Tracheoesophageal fistula 313
Tracheomalacia 312
Translabyrinthine fistula 159
Translation injury 537
Transtentorial herniation 30
Trauma 340, 528
Tree-in-bud appearance 280
Trevor's disease 509
Trichobezoar 382f
Tubercular arthritis 516, 516t
Tuberculoma 50, 51f, 259
Tuberculosis 249, 289f, 309, 319f, 383, 388
Tuberculous colitis 394
Tuberous sclerosis 9, 10f, 22, 56f, 281
Tubo-ovarian abscess complex 448
Tumor
benign 338, 456t
brown 198, 461
macrocystic 376
malignant 337, 456t
microcystic 376
mucinous 376
primary 318, 373
serous 376
supratentorial midline 12
Tumoral ossification 329
Typhlitis 393
U
Ulcerative colitis 392
Ulcerative proctitis 393f
Umbilical hernia 332f
Unicystic ameloblastoma 457f
Upper lobe, left 261f
Urachal anomalies 430
Ureter, ectopic 439
Ureterocele 434
Urinary bladder 433f
lesions 430
Urinoma 428
Uterine cancer 446
Uterine collection 444
Uterine leiomyoma 445
Uterine segment, lower 445f
Uterus 441, 443
Uveal melanoma 179, 180f
V
Vagina and vulva 441
Vaginal atresia 441, 442
Vaginal carcinoma 441, 443
Vaginal embryonal rhabdomyosarcoma 443
van Buchem disease 489
Varix, orbital 168
Vascular anomalies 157t
Vascular dementia 77, 79
Vascular disease 67, 104
Vascular malformation 3, 70
Vascular metastasis 310
Vascular scars 337t
Vascular tumors, malignant 164
Vasculitis 67, 74
Vein of Galen 33
Vena cava, inferior 409
Venous infarctions 73
Vertebra
expansile lesions of 499
multiple 499
part of 500
plana 470
posterior elements of 477f, 500t
Vertebral body 475
Vertebral neoplasm, primary 124
Vertebral pedicle erosion 502
Vertebrobasilar dolichoectasia 82
Vesical diverticulum 430
Viking horn sign 35
Villous adenoma 395
Virchow-Robin spaces 22, 42
Visceral disease 100
Vitamin K deficiency 75
von Hippel-Lindau disease 420
Vulvar carcinoma 441, 443
W
Waardenburg syndrome 155
Waldeyer's ring 217
Warburg's disease 164
Warburg's syndrome 176
Warthin's tumor 232, 232f, 252
Water lily sign 260
Weber Christian disease 399
Wegener's granulomatosis 164, 169, 186f, 201, 269, 524
White matter
diseases, differential diagnosis of 96, 96t
lesions 21
Wilms’ tumor 416, 425
Wilson's disease 25, 80, 99, 360
X
Xanthogranulomatous pyelonephritis 427
Z
Zellweger syndrome 66
Zenker's diverticulum 238
Zygomaticomaxillary suture 211
×
Chapter Notes

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BrainChapter 1

 
INTRACRANIAL CALCIFICATION
Details of intracranial calcification are given in Tables 1 and 2.
TABLE 1   Causes of intracranial calcification.
Criteria
Physiological
Pathological
Midline
  • Pineal
  • Habenular
  • Falcine
  • Interclinoid ligament
  • Pituitary
  • Third and fourth ventricular choroid plexus
  • Craniopharyngioma
  • Pinealoma
  • Chordoma/clival chondrosarcoma
  • Pituitary adenoma
  • Lissencephaly
Off-midline
Unilateral
Neoplasms
  • Meningioma
  • Ependymoma
  • Papilloma of choroid plexus
  • Dermoid/epidermoid/teratoma
  • Metastases2
Infections
  • Viral (CMV, herpes, rubella)
  • Bacterial (TB, Staphylococcus spp.)
  • Fungal (Coccidioides)
Infestations
  • Cysticercosis
  • Echinococcosis
  • Toxoplasmosis
  • Paragonimiasis
  • Trichinosis
  • Torulosis
Vascular
  • Atheroma
  • Glioma
  • Aneurysm
  • Angioma
  • Subdural/intraparenchymal hematoma
  • Sturge-Weber syndrome
Bilateral
  • Symmetrical
  • Asymme-trical
  • Choroid plexus
  • Basal ganglia
  • Dentate nucleus
  • Petroclinoid ligaments
  • Tentorial
  • Pacchionian bodies
  • Lipoma
  • Hypoparathyroidism
  • Pseudohypoparathyroidism
  • Fahr syndrome (Figs. 1A to E)
  • Neurofibromatosis
  • Glioblastoma multiforme
  • Tuberous sclerosis
(CMV: cytomegalovirus)
3
zoom view
Fig. 1A: Pictorial representation of common causes of intracranial calci- fication.
(AVM: aneurysm and vascular malformation; CMV: cytomegalovirus; PML: progressive multifocal leukoencephalopathy)
zoom view
Fig. 1B: Axial computed tomography (CT) images showing extensive intraparenchymal calcification in a case of Fahr's disease.
4
zoom view
Fig. 1C: Intracranial calcification in hypoparathyroidism.
zoom view
Fig. 1D: Intracranial calcification in pseudohypoparathyroidism.
zoom view
Fig. 1E: Intracranial lipoma with Bracket calcification.
5
TABLE 2   Differentiating features of various intracranial calcification.
Sites of calcification
Differentiating features
Comments
Pineal gland
It is seen as a punctate or nodular calcific density immediately posterior to the calcific density of habenular commissure
  • It is seen in most adults
  • It may be seen as early as 1 year of life and in 90% cases by 10 years of age
Habenular
  • It is usually 3–4 mm in diameter
  • It is seen as a crescentic, calcific commissure
The concavity of the crescent faces density at the back of the third ventricle posteriorly
Choroid plexus
It varies from punctate to large calcific density measuring up to 1 cm in diameter
Most common in the glomus at the trigone of lateral ventricle
Dural
It is seen as thin linear calcification of falx or sheet-like in cases of tentorium cerebelli
Commonly seen in the elderly
Petroclinoid ligaments
It is seen as a linear calcification extending from the tip of the dorsum sellae to the petrous apex
Commonly seen in the elderly
Interclinoid ligaments
It is seen as a thin linear calcification of ligaments between the clinoid processes
It gives rise to bridging sella extending across the midline appearance
Pacchionian bodies
They are seen as multifocal, punctate or nodular calcific densities usually near the vertex
They are usually bilateral and asymmetric in distribution
Pituitary gland
It is seen as a punctate calcification in the location of the gland in the sella
It is very rare and may be normal variant6
Basal ganglia and dentate nucleus
It is seen as amorphous calcification in the basal ganglia and dentate nuclei, usually in symmetrical and bilateral pattern
  • Globus pallidus is the first to calcify
  • This can be idiopathic or secondary to metabolic disorders
Glioma
  • Any type of glioma can show any pattern of calcification
  • Oligodendroglioma are the commonest to show calcification (approximately half of the cases)
Slow growing and the less malignant glioma are the most likely to reveal calcification
Craniopha- ryngioma
  • Punctate calcification is seen in three-fourths of the cases in children.
  • Occasionally, when the tumor is cystic, the calcification is curvilinear in the wall of the cyst with a characteristic location in midline just above the sella
The shape of the sella is changed as the anterior part is pressed downward from above
Meningioma
The calcification may be characteristically ball-like and amorphous in a characteristic parasagittal location and other specific sites
  • Hyperostosis in the adjacent calvarium and increased meningeal vascular markings upto the site of the bony lesion are other clues to the diagnosis
  • Heavily calcified meningiomas: Brain Rocks!!
Dermoid
  • They may show arcs of calcification
  • There may be associated central defect in the occipital bone in posterior fossa dermoid
  • They are most common in the posterior fossa and the base of the skull
  • Teratoma can also be seen in the pineal and suprasellar region7
  • Presence of the dental element confirms the diagnosis of the mature dermoid/teratoma
Lipoma
They show characteristic marginal calcification giving rise to the bracket configuration in the region of the corpus callosum
Less specific calcification may also be seen
Chordoma
It shows irregular calcification associated with soft tissue mass in the region of the clivus that may present into the nasopharynx after basal erosion
The calcification is, however, seen in minority of cases
Aneurysm
They show characteristic arc-like or circular marginal calcification
The most common site is the circle of Willis
Angioma
Small proportion of these show scattered flecks of calcification along with one or more rings or arc-like calcification
The arc-like calcification is seen in the aneurysmally dilated venous channels
Subdural hematoma
It shows typical marginal calcification of the membrane in concavo-convex configuration
Characteristic location of being adjacent to the calvaria is typical
Atheroma
Linear flecks of calcification in the carotid siphons secondary to atherosclerosis is very characteristic
Similar findings can occasionally be seen in other intracranial vessels8
Postinfect-ious/Post-infestation
  • Congenital toxoplasmosis typically shows linear streaks in the basal ganglia and multiple scattered calcific specks in the cortex (Figs. 2A and B)
  • Congenital CMV infection results in widespread periventricular calcification that may take the shape of the dilated ventricle; the calcification is typically stippled, bilateral and symmetric (Fig. 3)
  • Paragonimus westermani lesions are usually seen in the parietal region and often give rise to the extensive soap bubble calcification in the cysts that are usually 3–4 cm in diameter
  • Treated cases of tuberculoma, cysti-cerci, and toxoplasma may also result in nodular and punctate calcification at the site of the inactive lesion
  • Active tuberculoma and cysticercus may also reveal speck of calcification within the lesion
zoom view
Figs. 2A and B: Axial CT and lateral skull X-ray images in a case of congenital toxoplasmosis shows foci of calcification in left basal ganglia, bilateral periventricular region, and in left temporal lobe.
9
Neurofibro-matosis
Rare feature of neurofibromatosis is extensive calcification of the choroid plexi of the lateral and third ventricles
Tuberous sclerosis
  • Multiple, nodular, subependymal calcification are seen in this condition (Fig. 4)
  • Giant cell astrocytoma seen with this condition may also be the cause of calcification
The nodules are usually subcentimeter in size except in the case of the giant cell astrocytoma where larger nodules may be seen
Sturge-Weber syndrome (Figs. 5A to F)
  • It is characterized by gyral pattern of calcification typically extensive and bilateral involving the parieto-occipital cortex
  • The calcification resembles tram track configuration
The cortex showing calcification is typically atrophic and may show areas of intense postcontrast enhancement representing angiomas with large choroid plexi
Lissencephaly
Characteristic calcified nodule is seen in the septum pellucidum just behind foramen of Monro
The nodule is typically subcentimeter in size, usually 3–5 mm in diameter
(CMV: cytomegalovirus)
10
zoom view
Fig. 3: Axial CT image in a case of congenital cytomegalovirus (CMV) shows bilateral symmetrical periventricular calcification.
zoom view
Fig. 4: Axial CT image in a 10-year-old boy with tuberous sclerosis shows bilateral calcified subependymal nodules and a partially calcified tuber in left frontal lobe.
11
zoom view
Figs. 5A to E: Axial CT images showing features in a typical case of Sturge-Weber syndrome.
12
zoom view
Fig. 5F: Leukoencephalopathy with intracranial calcifications.
 
DIFFERENTIAL DIAGNOSIS OF BRAIN LESIONS
Details of differential diagnosis of brain lesions are given in Tables 3 and 4.
 
Supratentorial Midline Tumors
  • Optic and hypothalamic glioma
  • Craniopharyngioma
  • Astrocytoma
  • Pineoblastoma
  • Germinoma
  • Lipoma
  • Teratoma
  • Pituitary adenoma
  • Meningioma
  • Choroid plexus papilloma.
13
TABLE 3   Causes of space occupying lesions of brain.
Supratentorium
Infratentorium
Intra-axial (Table 6)
Cerebral hemisphere
  • Glioma (astrocytoma, oligodendroglioma, ependymoma, glioblastoma multiforme, gliomatosis cerebri)
  • Lymphoma
  • Parasitic cysts
  • Abscesses
  • Metastases
Pineal region
  • Germ cell tumor (germinoma, teratoma)
  • Pineoblastoma
  • Pineocytoma
  • Pineal cyst
Intraventricular
  • Astrocytoma
  • Primitive neuroectodermal tumor (PNET)
  • Choroid plexus papilloma
  • Meningioma
  • Medulloblastoma
  • Ependymoma, subependymoma
  • Giant cell astrocytoma
  • Central neurocytoma
  • Oligodendroglioma
  • Metastases
  • Colloid cyst
  • Hemangioblastoma
Corpus callosum
  • Lipoma
  • Glioblastoma multiforme
  • Lymphoma
Brainstem
  • Hematoma
  • Cavernous angioma
  • Glioma
Cerebellar hemisphere/vermis
  • Hematoma
  • Abscesses
  • Telangiectasia
  • Glioma
  • Ganglioglioma
  • Hemangioblastoma
  • Medulloblastoma
  • Pilocytic astrocytoma
  • Metastases
Fourth ventricle
  • Choroid plexus papilloma/carcinoma
  • Ependymoma/subependymoma
  • Medulloblastoma
  • Pilocytic astrocytoma
  • Dermoid/epidermoid
  • Hemangioblastoma
  • Metastases
  • Cysticercus
Foramen magnum
  • Astrocytoma
  • Hemangioblastoma14
Sellar and suprasellar
  • Pituitary adenoma
  • Metastases
  • Craniopharyngioma
  • Epidermoid, dermoid
  • Germinoma
  • Lymphoma
  • Lipoma
  • Opticochiasmatic/hypothalamic
  • Infundibular glioma
  • Neurosarcoid
  • Rathke cyst
  • Parasitic cyst
  • Hamartoma of the tuber cinereum
  • Histiocytosis
Extra-axial (Table 6)
Suprasellar
  • Arachnoid cyst
  • Parasitic cyst
  • Meningioma
  • Osteocartilaginous tumors
Parasellar
  • Vascular tumors (internal carotid artery aneurysm)
  • Cavernous sinus lesions
    • Hemangioma Hemangiopericytoma
    • Meningioma
    • Lymphoma
    • Metastases
    • Neural tumors (Schwannoma, neurofibroma)
    • Intracranial aneurysm (ICA)
Cerebellopontine angle
  • Schwannoma (V, VIII) (Fig. 6)
  • Meningioma
  • Epidermoid
  • Metastases
  • Paraganglioma
  • Arachnoid cyst
  • Lipoma
  • Cholesterol granuloma
  • Lymphoma
  • Sarcoidosis
  • Bony tumors from the petrous bone
Skull base
  • Posterior cranial fossa lesions
    • Nerve sheath tumor
    • Paraganglioma
    • Meningioma
    • Metastases15
zoom view
Fig. 6: An intensely enhancing extra-axial mass lesion seen in left cerebellopontine (CP) angle cistern with intracanalicular extension suggestive of acoustic Schwannoma.
Skull base
  • Anterior cranial fossa lesions
    • Invasive polyposis
    • Inverted papilloma
    • Meningioma
    • Malignant sinonasal masses
    • Lymphoma
    • Esthesioneuroblastoma
    • Metastases
    • Mucocele
    • Encephalocele
    • Dermoid cyst
    • Osteoma
    • Osteomyelitis secondary to sinusitis
  • Middle cranial fossa lesions
    • Metastases
    • Malignant nasopharyngeal lesions
Foramen magnum
  • Meningioma
  • Schwannoma
  • Metastases
  • Paraganglioma
  • Epidermoid
  • Arachnoid cyst
  • Tumors arising from the clivus and skull base
Tentorial
  • Meningioma
Epidural lesions
  • Hematoma
  • Abscess
  • Soft tissue mass arising from bony lesions the skull vault16
    • Juvenile nasopharyngeal angiofibroma
    • Osteomyelitis secondary to sinusitis
    • Granulomatous sinusitis (Wegener's granulomatosis)
    • Lymphoma
    • Meningioma
    • Chordoma
    • Leprosy
    • Sarcoidosis
    • Tuberculosis
    • Myeloma
Dural/falcine/subdural lesions
  • Hematoma
  • Effusion/empyema
  • Sarcoidosis and histiocytosis (Rosai- Dorfman disease)
  • Arteriovenous (AV) malformation
  • Meningioma (en plaque)/meningiosarcoma
  • Hemangioma/hemangiopericytoma
  • Metastases (leukemic and lymphoma deposits)
Epidural lesions
  • Hematoma
  • Abscess
  • Soft tissue mass arising from the skull vault
17
TABLE 4   Causes of brain tumors in the pediatric age group.
Presenting at birth
Presenting at a later age
  • Choroid plexus papilloma/carcinoma
  • Craniopharyngioma
  • Ependymoma
  • Hypothalamic astrocytoma
  • Medulloblastoma
  • Primitive neuroectodermal tumor (PNET)
  • Teratoma
  • Astrocytoma
  • Choroid plexus papilloma
  • Colloid cyst
  • Craniopharyngioma
  • Ependymoma/subependymoma
  • Germinoma
  • Hamartoma
  • Medulloblastoma
  • Meningioma
  • Metastases
  • Oligodendroglioma
  • Optic nerve glioma
  • Pinealoma
  • Teratoma
 
Supratentorial Midline Cysts
  • Cavum septum pellucidum (5th ventricle)
  • Cavum vergae (6th ventricle)
  • Cavum velum interpositum
  • Arachnoid cyst in the region of the quadrigeminal plate cistern
  • Vascular lesions (aneurysm)
  • Cholesterol granuloma
  • Pineal cyst
  • Rathke's cleft cyst
 
Supratentorial Paramidline Cysts
  • Epidermoid
  • Trichilemmal cyst (sebaceous)
  • Leptomeningeal cyst
  • Arachnoid cyst (middle cranial fossa/convexity)18
 
PSEUDOMASSES OF BRAIN
Pseudomasses of brain are shown in Table 5.
TABLE 5   Causes of pseudomasses of the brain.
Supratentorium
Infratentorium
Intra-axial
Pineal region
  • Enlarged suprapineal recess
  • Enlarged cavum velum interpositum
Intraventricular
  • Subependymal giant cell tumor
  • Enlarged calcified choroid plexus
Sellar and suprasellar
  • Encephalocele
Vermis
  • Superior vermis
Fourth ventricle
  • Prominent choroid plexus
Extra-axial
Suprasellar
  • Empty sella
  • Congenital ectopic neurohypophysis
Parasellar
  • Vascular tumors (caroticocavernous fistula, cavernous thrombosis)
Dural/falcine/subdural lesions
  • Thrombosis
Cerebellopontine angle
  • Enlarged flocculonodular lobe of cerebellum
  • Prominent choroid plexus from foramen of Luschka
Foramen magnum
  • Tonsillar herniation
Skull base
  • High jugular bulb
  • Jugular vein thrombosis
  • Prominent jugular tubercles19
 
INTRACRANIAL MASSES
Details of intracranial masses are shown in Table 6.
TABLE 6   Differentiating features between intra-axial and extra-axial intracranial masses.
Features
Intra-axial
Extra-axial
Local bony changes
Usually absent until late in the disease
Commonly seen
Dural tail
Absent
May be seen
Cerebrospinal fluid (CSF) cleft
Absent
Present
Effect on adjacent subarachnoid spaces and cisterns
Effaced to variable degree
Enlarged to variable degree
Feeding vessels
Pial source
Dural source (Meningioma has dual blood supply from dural as well as pial arteries)
Buckling of gray/white matter junction
Absent
Present
White matter bucking sign
Absent
Present
Intervening gray matter between mass lesion and white matter
Absent
Present
Rotation of the brainstem in infratentorial lesions
Absent
Present (toward the contralateral side)
20
 
NONTUMORAL BRAIN LESIONS
Nontumoral brain lesions are given in Table 7.
TABLE 7   Causes of hypodense, nonenhancing lesions.
Soft tissue
Fluid
Fat
Air
With mural nodule
Without mural nodule
  • Edema
  • Infarct
  • Nonhemorrhagic contusion (Fig. 8)
  • Encephalitis (including limbic)
  • Gliosis
  • Periventricular cerebrospinal fluid (CSF) seepage
  • Demyelinating diseases
  • Leukodystrophies
  • Gliomatosis cerebri
  • Neurocysticercosis (granular nodular)
  • Toxo- plasmosis
  • Chronic infarcts
  • Virchow-Robin spaces
  • Chronic hematoma
  • Encephalo-malacia
  • Porencephaly
  • Schizence-phaly
  • Neurocysti-cercus (vesicular, colloid vesicular)
  • Hydatid cyst
  • Arachnoid cyst
  • Choroid plexus cyst
  • Choroid fissure cyst
  • Ependymal cyst
  • Epidermoid
  • Lipoma
  • Dermoid
zoom view
Fig. 7: Axial CT image showing multiple aeroceles in the basal cisterns.
21
zoom view
Fig. 8: Contrast-enhanced computed tomography (CECT) axial image of head hypodense area with loss of gray-white matter differentiation in a case of head trauma suggesting nonhemorrhagic contusion.
 
WHITE AND GRAY MATTER LESIONS
Details of white and gray matter lesions are given in Tables 8 and 9.
TABLE 8   Causes of myelinating/demyelinating lesions.
White matter (Leukodystrophy)
Gray matter (Poliodystrophy)
Both gray and white matter
  • Multiple sclerosis
  • Vascular disease
  • Diffuse axonal injury
  • Postinfectious demyelination
  • Toxic demyelination
  • Metachromatic leukodystrophy (MLD)
  • Krabbe disease
  • Adrenoleuko-dystrophy (ALD)
  • Pelizaeus-Merzbacher disease (PMD)
  • Alexander disease
  • Canavan disease
  • Aminoaciduria
  • Lipidoses
  • Mucopoly- saccharidoses
  • Mucolipidosis
  • Fucosidosis
  • Glycogen storage diseases
  • Mitochondrial encephalopathies [myoclonic epilepsy with ragged red fiber (MERRF); mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS)]
  • Peroxisomal disorders
22
TABLE 9   Characteristic pattern involvement in leukodystrophy/demyelinating diseases.
Characteristic patterns
Diseases involved
Diffuse lobar involvement
  • Canavan disease
  • Pelizaeus-Merzbacher disease
  • 4H syndrome
Predominantly frontal white matter involvement
Alexander disease
Predominantly occipital white matter involvement
Adrenoleukodystrophy
Associated with enlarged ventricles
  • Alexander disease
  • Canavan disease
Associated with hyperdense basal ganglia
Krabbe disease
Associated with focal hypodensity in basal ganglia
  • Alexander disease
  • Canavan disease
  • Metachromatic leukodystrophy
Associated with postcontrast enhancement
  • Adrenoleukodystrophy
  • Alexander disease
 
Multifocal White Matter Lesions
  • Virchow-Robin spaces (when bilateral and diffuse, these are called Etate Crible)
  • Demyelinating diseases (vascular, postinfectious) (Table 9)
  • Multiple sclerosis (MS)
  • Diffuse axonal injury
  • Cysticerci
  • Abscesses
  • Leukoencephalopathy
  • Neurocutaneous syndromes [tuberous sclerosis, neurofibromatosis-1 (NF-1)]
  • Multifocal glioma
  • Primary CNS lymphoma
    • Progressive multifocal leukoencephalopathy (PML)
    • Encephalitis
    • Iris23
  • Gliomatosis cerebri
  • Metastases.
 
Periventricular Hypodensity
  • Gliosis
  • Encephalomalacia
  • Porencephaly
  • Resolving hematoma
  • Infarct
  • Interstitial seepage of cerebrospinal fluid (CSF) in hydrocephalus
  • Multiple sclerosis
  • Migraine
  • Vasculitis
  • Encephalitis
  • Acute disseminating encephalomyelitis
  • Diffuse necrotizing leukoencephalopathy
  • Progressive multifocal leukoencephalopathy
  • Virchow-Robin space
  • Leukodystrophy.
 
Brainstem Hypodensity
Brainstem hypodensity is given in Table 10.
  • Physiological
  • Syringobulbia
  • Infarction
  • Central pontine myelinolysis
  • Gliosis
  • Glioma
  • Metastases
  • Granuloma.
 
Bilateral Focal/Diffuse Hypodensities Basal Ganglia
  • Physiological (VR spaces)
  • Infection (TB, HIV)/infestation (toxoplasmosis, cryptococcosis)
  • Arterial infarct (lacunar infarcts)
  • Venous infarct (internal cerebral vein thrombosis)24
TABLE 10   Causes of hyperdense brain lesions.
Nonenhancing lesions
Enhancing lesions
  • Acute hematoma (Figs. 9 and 10)
  • Capillary/cavernous angioma
  • Colloid cyst
  • Calcified lesions
  • Tuberculoma
  • Neurocysticercus
  • Lymphoma
  • Meningioma
  • Medulloblastoma
  • Choroid plexus papilloma
  • Tumors with matrix calcification [oligodendroglioma, glioblastoma, ependymoma, capillary/cavernous angioma, arteriovenous malformation (AVM)]
  • Metastases [mucinous primary tumor—gastrointestinal tract (GIT), ovary, pancreas, melanotic melanoma osteosarcoma]
zoom view
Fig. 9: Axial CT image shows lentiform shaped acute extradural hematoma along the lateral parietal convexity.
zoom view
Fig. 10: Axial CT image showing acute subdural hematoma along right frontoparietal lateral convexity with a coincidental small hemorrhagic contusion in right parietal lobe.
25
  • Hypoxic—ischemic encephalopathy
  • Metabolic encephalopathy (severe hypoglycemia, osmotic myelinolysis)
  • Toxic encephalopathy (methyl alcohol, CO, cyanide)
  • Inherited disorders (Alexander disease, Canavan disease, Hallervorden Spatz disease, Huntington disease, Leigh disease, metachromatic leukodystrophy, methylmalonic aciduria, Wilson disease)
  • Acquired neurodegenerative disorders (MS, Parkinson disease, striatonigral degeneration).
 
Bilateral Hyperdense (Calcification) Basal Ganglia
  • Idiopathic (Globus pallidus is most commonly affected)
  • Fahr disease
  • Toxic causes: CO poisoning, lead poisoning, mineralizing angiopathy.
  • Secondary to infection (TB, HIV, TORCH)/infestation (toxoplasmosis, cysticercosis)
  • Congenital disorders (Cockayne syndrome, Down syndrome, MELAS/MERRF (mitochondrial encephalopathy with lactic acidosis/myoclonic epilepsy with ragged red fiber) syndrome, methemoglobinopathy, neurofibromatosis, tuberous sclerosis)
  • Metabolic: Hypoparathyroidism, pseudohypoparathyroidism, pseudopseudohypothyroidism, hyperparathyroidism.
  • Miscellaneous: Postradiotherapy/chemotherapy.
 
Hyperdense Falx
  • Subarachnoid hemorrhage (associated with sulcal bleed in the parasagittal brain parenchyma)
  • Subdural hemorrhage
  • Diffuse cerebral edema (there is pseudohyperdensity due to diffusely hypodense brain parenchyma)
  • Dural calcification (usually seen in the elderly population)
  • Normal variant (usually seen in the children).26
 
Ring Enhancing Lesions Crossing the Corpus Callosum
  • Glioblastoma multiforme (butterfly glioma): More heterogeneous with areas of necrosis and hemorrhage
  • Astrocytoma
  • Oligodendroglioma:
    • Lymphoma: Primary lymphoma is usually homogeneous and does not show necrosis/hemorrhage. Secondary lymphoma or lymphoma associated with immunocompromised states (AIDS) show necrosis.
 
Innumerable Small Enhancing Brain Nodules (Table 11)
  • Disseminated infection: Tuberculosis (TB), neurocysticercosis (NCC), and histoplasmosis
  • Inflammation: Sarcoidosis, MS
  • Primary CNS lymphoma
  • Metastases
  • Subacute multifocal infarction: Hypoperfusion, multiple emboli, cerebral vasculitis, meningitis, cortical vein thrombosis.
 
Gyriform Enhancement (Table 12)
  • Infarct
  • Leptomeningitis (Fig. 11)
  • Sequelae to subarachnoid hemorrhage
 
Pneumonic for Ring Enhancing Lesions in Brain
 
MAGICAL DR
M:
Metastasis
A:
Abscess
G:
Glioblastoma
27
TABLE 11   Causes of hypodense, enhancing lesions.
Ring enhancement (Fig. 12)
Nonring enhancement
  • Infectious:
    • Abscess/empyema
    • Granuloma
    • Fungal (cryptococcosis)
  • Parasitic:
    • Cysticercus
    • Toxoplasmosis
  • Neoplastic:
    • Primary (anaplastic astrocytoma, CNS lymphoma in AIDS patient)
    • Metastatic
  • Miscellaneous:
    • Subacute infarct
    • Subacute hematoma
    • Non-neoplastic cysts (Rathke's cleft cyst, colloid cyst)
    • Multiple sclerosis
    • Thrombosed aneurysm/vessel/AVM
  • Postictal edema
  • Cerebritis
  • Brain tumors (majority)
(AIDS: acquired immunodeficiency syndrome; AVM: arteriovenous malformation; CNS: central nervous system)
TABLE 12   Causes of ependymal enhancement (Fig. 11).
Focal
Diffuse
  • Prominent subependymal veins (physiological, collateral veins secondary to dural sinus occlusion)
  • Subependymal nodules
  • Subependymal giant cell astrocytoma
  • Nodular heterotopia
  • Subependymal cysticercus
  • Neoplastic (lymphoma, infiltrating glioma, medulloblastoma, carcinomatosis)
  • Infection (pyogenic, CMV, ependymitis granularis)
  • Neoplastic (lymphoma, infiltrating glioma, pineal tumors, medulloblastoma, carcinomatosis)
  • Postchemotherapy and shunt placement
28
zoom view
Fig. 11: Coronal MPR CT image with nodular enhancement of the leptomeninges and ependymal enhancement.
zoom view
Fig. 12: Axial CT image showing a ring-enhancing lesion with perilesional edema in the left frontoparietal region.
29
I:
Infarct (subacute phase)
C:
Contusion
A:
AIDS
L:
Lymphoma
D:
Demyelinating disease
R:
Radiation necrosis or resolving hematoma
 
Multifocal Brain Tumors and Tumor-like Lesions
  • Infections and infestations [tuberculoma, toxoplasmosis, NCC, multiple abscesses (pyogenic/fungal)]
  • Multiple sclerosis
  • Phakomatosis
  • Metastases from primary CNS tumor
  • Multicentric CNS lesion: True multicentric glioma, primary CNS lymphoma
  • Multicentric meningioma without neurofibromatosis.
 
VENTRICULAR LESIONS
 
Ventricular Enlargement
  • Hydrocephalus
  • Holoprosencephaly
  • Hydranencephaly
  • Schizencephaly
  • Porencephaly
  • Encephalomalacia
  • Deep cortical atrophy.
 
Small Ventricles
  • Physiological variation (sulci and cisterns appear normal)
  • Chronic ventricular shunt drainage (sulci and cisterns appear normal)
  • Increased intracranial pressure (sulci and cisterns appear effaced).30
 
Abnormal Ventricular Configuration
  • Colpocephaly (dilatation of the trigone and occipital horns of the lateral ventricles):
    • Corpus callosal agenesis
    • Arnold-Chiari malformation
    • Holoprosencephaly (lobar type).
  • Abnormal frontal horns:
    • Square or box-like—absence or hypoplasia of septum pellucidum (septo-optic dysplasia, callosal dysgenesis, schizencephaly, holoprosencephaly)
    • Convex or flat lateral wall (caudate lobe atrophy).
  • Miscellaneous:
    • Schizencephaly (nipple-like elevation along the lateral wall)
    • Porencephaly
    • Corpus callosum dysgenesis (high riding third ventricle with communication with a dorsal interhemispheric cyst)
    • Chiari II malformation (elongated, slit-like fourth ventricle)
    • Dandy-Walker syndrome (communication between the fourth ventricle and the retrocerebellar cyst) (Figs. 13A and B)
    • Dandy-Walker variant (slit-like communication between the fourth ventricle and the cisterna magna with a typical key-hole appearance) (Figs. 14A and B)
    • Ventricular diverticulum (CSF-outpouching from the medial atrial wall of the lateral ventricle)
    • Herniation
      • Subfalcine: It is characterized by displacement of the lateral and third ventricle under the falx away from the side of mass lesion with dilatation of the contralateral lateral ventricle (Fig. 15).
      • Transtentorial herniation: There is change in size and configuration of the fourth ventricle depending upon the ascending or descending transtentorial herniation. Ascending type is associated with compression and displacement of the third ventricle and its aqueduct as well while descending type is characterized by dilatation of the ambient, quadrigeminal, and cerebellopontine cisterns and rotation of the brainstem.31
zoom view
Figs. 13A and B: Axial CT images showing Dandy-Walker syndrome.
zoom view
Figs. 14A and B: CECT axial images of head showing hypoplastic vermis and fourth ventricle communicating with cisterna magna in a case of Dandy-Walker variant.
32
 
Hydrocephalus
  • There is enlargement of part or entire ventricular system with proportionate enlargement of the temporal horns of the lateral ventricles (Fig. 16)
  • There is rounding of the frontal horns of the lateral ventricle
  • There is effacement of the basal cisterns, fissures, and the sulcal spaces to a varying degree
  • There is transependymal seepage of the CSF resulting in periventricular hypodensity in moderate and severe cases
  • The dilated ventricles are always surrounded by cortical mantle irrespective of the severity.
zoom view
Fig. 15: Axial CT image showing subfalcine herniation of the right lateral ventricle to the left side in a patient with acute SDH on right side with a small aerocele.
(SDH: subdural hematoma)
33
zoom view
Fig. 16: Axial CT image of the brain showing hydrocephalus with dilatation of all the ventricles.
 
Holoprosencephaly
The CT appearance varies with the type of the holoprosen-cephaly.
 
Alobar Type
It is characterized by:
  • Single, large, crescentic ventricle devoid of horns
  • Large dorsal cyst with a wide communication with the ventricle
  • Grossly distorted supratentorial brain morphology with no hemispheric development and absence of the interhemispheric fissure, falx, and tentorium, septum pellucidum, third ventricle, corpus callosum, Sylvian fissure, straight sinus, vein of Galen, and internal cerebral veins
  • Fused thalami and basal ganglia protruding into the ventricle
  • Cortical mantle is seen in the posterosuperior part of the cranium and is usually pachygyric34
  • Midbrain, pons, and cerebellum are morphologically normal
  • Associated abnormalities include cyclopia, ethmocephaly, cebocephaly, cleft lip, and palate.
 
Semilobar Type
It is characterized by:
  • Single, large ventricle with rudimentary or poorly developed temporal and occipital horns
  • Large dorsal cyst with a wide communication with the ventricle
  • Supratentorial brain morphology is distorted with no hemispheric development and rudimentary interhemispheric fissure (separating occipital lobes), falx, and tentorium, third ventricle, but with absence of septum pellucidum and corpus callosum, Sylvian fissure, straight sinus, vein of Galen, and internal cerebral veins
  • There is partial separation of the thalami and basal ganglia that are anterior relative to their usual location
  • Cortical mantle seen is thicker than in alobar type and is pachygyric
  • Midbrain, pons, and cerebellum are morphologically normal
  • Associated abnormalities include cleft lip and palate.
 
Lobar Type
It is characterized by:
  • Two distinct, well-formed lateral ventricles with closely apposed bodies
  • The ventricles are dilated with relatively greater enlargement of the occipital horns of the lateral ventricle
  • The frontal horns are fused due to absence of the septum pellucidum and dysplastic frontal lobes, falx, and interhemispheric fissure
  • Sylvian fissures are absent
  • Corpus callosum is usually present35
  • Thalami and basal ganglia may be fused or separated
  • Cortical mantle is usually pachygyric and lissencephalic
  • Midbrain, pons, and cerebellum are morphologically normal
  • Associated abnormalities include cleft lip and palate.
 
Hydranencephaly
  • There is a large CSF—isodense, cystic lesion surrounded by a membrane with no identifiable brain tissue usually involving one half of the cranial cavity
  • Hemispheric division is usually maintained
  • Except for the atrophic brainstem, rest of the brain appears morphologically normal even on the side of the cyst
  • Ventricle with the choroids plexus are usually preserved.
 
Atrophy
  • It is characterized by symmetric enlargement of the ventricular system with proportionate enlargement of the basal cisterns, fissures, sulcal spaces, and the other CSF spaces in the cranial cavity
  • It is associated with loss of volume of both gray and white matter with reduction in gray white matter differentiation.
 
Corpus Callosum Agenesis (Fig. 17)
  • It is characterized by absence of corpus callosum, cingulated gyrus, and sulcus with a high riding third ventricle opening into the interhemispheric fissure. A cyst may or may not be present.
  • The medial hemispheric surface of the brain shows a radial arrangement of the gyri and sulci in a spoke-wheel like configuration.
  • Abnormal upward course of the anterior cerebral arteries (ACAs).
  • The lateral ventricle are arranged parallel to each other (Racing car sign)with pointed frontal horns (Viking horn sign) and dilated atria and Brain occipital horns
36
zoom view
Fig. 17: Axial CT image shows parallel oriented lateral ventricles with colpocephaly with absence of corpus callosum.
  • With partial agenesis, rostrum and splenium of the corpus callosum are hypoplastic or absent with varying degrees of development of the body and genu.
 
Arnold-Chiari Malformation
  • Type II is the classical type in this group and is commonly associated with colpocephaly
  • It is characterized by small posterior fossa, with low lying transverse sinuses and concave clivus and petrous ridges
  • There is beaking of tectum, creeping of cerebellum around brainstem with inferiorly displaced vermis and medullary spur and kink
  • There is hydrocephalus with tube-like, elongated fourth ventricle
  • Meningomyelocele is invariably seen with syringomyelia and diastematomyelia in many cases
  • Associated anomalies in the brain include corpus callosum dysgenesis, polymicrogyria, and heterotopias.37
 
DIFFERENTIATING FEATURES OF BRAIN LESIONS
Differentiating features of brain lesions are listed in Table 13.
TABLE 13   Differentiating features of various brain lesions.
Diseases
Differentiating features
Comments
Edema (Fig. 18)
  • Ill-defined area of nonenhancing hypodensity involving primarily the white matter
  • Mass effect is evident in form of flattening of gyri, displacement, and deformation of ventricles and even midline shift
  • Cytotoxic: Ischemia/anoxia
  • Vasogenic: Commonest, associated with neoplasms, metastases hemorrhagic infarction, and inflammation
Arterial infarct (Fig. 19)
  • It is seen as well-defined lesion involving both gray and white matter conforming to an arterial territory that may show ring or gyriform enhancement in subacute stage
Larger infarcts may show hemorrhagic transformation in the form of petechial or frank hemorrhage
  • Indirect signs include hyperdense clot in MCA; subtle effacement of sulci and fissures; obscuration of gray and white matter interface and hypodensity of insular cortex
Nonhemo-rrhagic contusion
  • It is seen as a hypodense, nonenhancing, ill-defined lesion affecting both gray and white matter
  • Gyral enhancement can be seen in the resolving stage
History of trauma can be elicited38
zoom view
Fig. 18: Axial CT image shows nonenhancing edema around the ring enhancing lesion
zoom view
Fig. 19: Axial CT image a large right cerebral acute arterial infarct.
Gliosis
It is seen as an ill-defined lesion involving both gray and white matter with signs of volume loss on ipsilateral side with dilatation of the ipsilateral ventricle, fissure, and sulci
It may be due to any type of insult to the brain parenchyma (vascular or inflam- matory or traumatic)
Periventri-cular CSF seepage
It is seen as a marked, white matter hypodensity along the contour of the ventricular system, most prominent at the horns
It is associated with moderate-to-severe hydrocephalus
Lipoma
  • It is typically seen as a curvilinear, midline, non- enhancing, fat attenuating mass taking the shape of the corpus callosum, when the latter is normal
Dorsal, pericallosal region is the most common site followed by basal cisterns (Figs. 20A and B)39
zoom view
Figs. 20A and B: Axial CT images show a fat density lesion in left ambient cistern suggestive of lipoma.
  • In cases of corpus callosal dysgenesis, the mass is tubulonodular in shape
  • Calcification may be seen in curvilinear (bracket- shaped) or nodular
Hemangio- blastoma
It is seen as a sharply marginated mass of CSF density with peripheral, intensely and homogeneously, enhancing mural nodule
  • It may be associated with von Hippel-Lindau disease
  • The size of the tumor and mural nodule is less than pilocytic astrocytoma40
Neuro-cysticercus (Figs. 21A to C)
  • The CT appearance varies with the stage of the disease
  • In vesicular stage, the lesion is seen as a sub-centimeter cystic focus with imperceptible walls at gray white matter junction or in subpial location. There is no edema or enhancement
  • In vesicular nodular stage, there is a cystic lesion with usually an eccentric, hyperdense nodule with perilesional edema and variable postcontrast enhancement
  • Granular nodular stage shows appearance similar to the previous stage but with greater postcontrast enhancement and edema
  • Nodular calcified stage is characterized by nodular focus of calcification with no postcontrast enhancement or edema
  • When multiple, the lesions are seen in different stages
When multiple, lesions are seen in different stages (vesicular, colloid vesicular, granular nodular, nodular calcified), with edema around some lesions corresponding to the middle two stages
Toxo-plasmosis
  • It is characterized by solitary or multiple, ring-enhancing lesions with edema in immunocompromised patients. Target appearance is characteristic
  • It is the most common opportunistic infection in acquired immunodeficiency syndrome (AIDS) patients41
zoom view
Figs. 21A to C: Axial CT scans showing colloid vesicular and granular nodular and nodular calcified stage of cysticercus.
  • Hemorrhage and calcification is common in treated patients
  • It is seen as multifocal, calcified lesion in the region of basal ganglia, periventricular white matter, and cortex in cases of congenital infection and is commonly associated with hydrocephalus
  • The most common differential diagnosis is AIDS-related lymphoma
  • Multiplicity of the lesions favor toxoplasmosis
  • It is the second most common congenital infection after CMV infection42
Cryptoco-ccosis
  • It is seen as multifocal, cystic lesions with variable postcontrast enhancement in the region of basal ganglia and midbrain with absence of edema
  • The most common differential diagnosis is VR spaces
Diffuse disease in the form of cryptococcomas is common in AIDS patients while menin- gitis is common in immunocompetent patients
Chronic infarct (Fig. 22)
  • It is seen as a well-defined, hypodense to CSF attenuating lesion corresponding to the vascular territory and involving both gray and white matter
  • No evidence of volume loss is seen
Usually refers to the infarct older than 8 weeks
Virchow-Robin spaces (VR spaces)
  • It refers to the CSF attenuating oval lesions with their long axis perpendicular to the body of the ventricle
  • They are usually multiple
  • They are commonly seen in the ganglionic region and periventricular region
  • Dilated VR spaces are also seen in cryptococcal infection in AIDS patient
Hematoma
  • The CT appearance varies with the age of the hematoma
  • Acute hematoma appears hyperdense
  • Subacute hematoma appears isodense to the gray matter and may show some ring enhancement on postcontrast images
  • Chronic hematoma is hypodense and does not show evidence of enhancement
History of trauma or hypertension is suggestive43
zoom view
Fig. 22: Axial CT image showing chronic infarct in left cerebellar hemisphere.
Encepha-lomalacia
Ill- or well-defined CSF attenuating lesion with signs of volume loss
It resembles gliosis in appearance but is lower in attenuation value
Porence-phalic cyst (Fig. 23)
  • It is a well-defined, intra-axial, CSF attenuating lesion involving both gray and white matter but is surrounded by white matter
  • It may or may not communicate with the ventricular system
The differentiation is to be made with arachnoid cyst and schizencephaly44
Schizen-cephaly (Fig. 24)
  • It is seen as an extra-axial CSF collection that is communicating with the ventricular system through a gray matter lined cleft in the brain matter
  • The open lip type shows a clear communication between the collection and ventricular system
  • In the closed lip type, cleft is often not visualized but the diagnosis is suggested by a nipple-like projection in the lateral wall of the ipsilateral lateral ventricle
  • The condition can be bilateral and may be associated with congenital malformation of the brain
  • Heterotopias are commonly associated
zoom view
Fig. 23: A cerebrospinal fluid (CSF) containing cavity seen in right frontal lobe communicating with the frontal horn of right lateral ventricle suggestive of porencephalic cyst.
zoom view
Fig. 24: Bilateral schizencephaly—open lip on left side and closed lip on right side.
45
Hydatid cyst
  • It is seen as a spherical, intra-axial, CSF attenuating lesion with thin, nonenhancing walls
  • It may be multiple and gliomatosized
The most common site is the parietal region
Choroid plexus cyst
  • It is seen as a CSF attenuating lesion within the choroid plexus of the ventricle
  • It is usually bilateral
It may be an incidental finding
Choroid fissure cyst
It is seen as a well-defined, CSF attenuating lesion with no postcontrast enhancement in the choroidal fissure. The latter is located between the dien- cephalon and hippocampus
It is usually discovered incidentally
Ependymal cyst
  • It is seen as a well-defined, CSF attenuating, nonenhancing lesion lying within the ventricular system commonly in the atria
  • The lesion is unrelated to the choroid plexus of the ventricles and is usually unilateral and may just be seen as focal enlargement of the ventricle
Large cyst may present with obstructive hydrocephalus
Arachnoid cyst (Figs. 25A and B)
  • It is seen as a well-defined, CSF attenuating, extra-axial lesion with no communication with the ventricular system
  • There may be mass effect on the adjacent structures as scalloping of the inner table of the skull
  • There is no edema/enhancement/internal septa
  • The most common site is the temporal region in the Sylvian fissure
  • It may be idiopathic or secondary to meningitis46
zoom view
Figs. 25A and B: Axial CT images showing arachnoid cyst in the left cerebellopontine angle.
Epidermoid (Figs. 26A and B)
  • It is typically seen as a lobulated, homogeneous, nonenhancing, extra-axial, off-midline mass of CSF or fat density
  • It engulfs the vessels; cisternal and fissures insinuation is characteristic
  • It molds itself around the brain surface
  • Calcification is uncommon and the periphery may show occasional enhancement
The most common site is the basal cisterns especially the cerebellopontine cistern
Dermoid
  • It is seen as a rounded, midline, fat attenuating, nonenhancing mass usually seen in the parasellar and basifrontal region
  • Mural calcification is common but enhancement is almost never seen unless infected
  • Basifrontal type may be associated with dermal sinus tract
Rupture is commoner than epidermoid47
zoom view
Figs. 26A and B: CECT axial images of head showing fluid density extra-axial lesion on left side of posterior fossa insinuating along the subarachnoid spaces suggestive of epidermoid.
(CECT: contrast-enhanced computed tomography)
Capillary/cavernous angioma (Figs. 27A to C)
  • They are iso- to hyperdense on NECT with variable degree of enhancement in capillary type and absent or minimal in cavernous type
  • Calcification is common
  • Edema and mass effect are almost never seen
Capillary type has a predilection for brainstem
Abscess
  • It is seen as a ring enhancing lesion on CECT with variable thickness of smooth, regular walls and surrounding edema and mass effect
  • Granulomatous abscesses have thicker, nodular, and hyperdense walls with lobulated shape
  • Associated ependymal and meningeal enhancement are commonly seen
  • The closest differential diagnosis is necrotic mass where the walls are relatively thicker and irregular and nodular with thicker wall on ependymal side
  • Abscesses seen in systemic diseases (leukemia, lymphoma) associated with immunosuppression resemble necrotic masses48
zoom view
Figs. 27A to C: Axial, coronal, and sagittal CT images showing acavernous angioma in the pons on left side.
  • The wall on the ependymal side appear thinner than the one toward the cortex
  • The presence of satellite nodules and air are characteristic
  • An abscess can be thin-walled with minimal mural enhancement with minimal or no edema in chronic stage or when patient is on steroid therapy
49
Empyema
  • It is seen as an extra-axial, hypodense collection with enhancing walls and often with edema in the adjacent brain parenchyma
  • Enhancing septae are sometimes evident
  • Cerebral convexity and interhemispheric fissure are the common sites
They are commonly associated with meningitis, chronic suppurative otitis media (CSOM), trauma, or post-operative condition
Aeroceles
The CT HU value ranges from −100 to −1,000
The important causes include trauma and neoplasm invading sinus
Colloid cyst
  • It is seen as a hyperdense but sometimes as a isodense, round mass at the inferior aspect of the septum pellucidum protruding into the anterior portion of the third ventricle between the columns of the fornix on NECT
  • CECT shows mild to absent enhancement
It is usually an incidental finding but may present with features of increased intracranial pressure
Rathke cleft cyst
  • It is usually seen as hypodense, noncalcified, rim enhancing, intra- and suprasellar lesion
  • It may be entirely intra- or suprasellar in location
It is commoner in females
Entero-genous cyst
It is seen as a well-defined, lobulated, hypodense, nonenhancing, extra-axial lesion commonly seen in the cerebellopontine angle cistern and anterior to the brainstem
These are very rare lesions; commoner in the spine50
Tuber-culoma (Figs. 28 and 29)
  • It is seen on noncontrast images as an iso- to hyperdense, ring or nodular lesion usually at the gray white matter interface with significant perilesional edema
  • On postcontrast images, it shows moderate, nodular, or ring enhancement
  • The lesion is usually larger than 1 cm in diameter with irregular, nodular walls
  • Mature tuberculoma can appear as target lesions with central or eccentric, punctate calcified, or enhancing hyperdensity
  • Multiple, conglomerate masses with associated basilar meningitis are highly suggestive of the diagnosis
In pediatric age, these are commonly seen in the infra-tentorium; while in the adult, it is commonly supratentorial
Lymphoma
  • It is characterized as multiple, hyperdense, centrally located (deep white matter, basal ganglia, corpus callosum), mild-to-moderately and homogeneously enhancing, nodular lesions
  • Subependymal spread is common
  • Hemorrhage and ring enhancement is commonly seen in cases associated with AIDS
  • Primary cerebral lymphoma is usually of the non-Hodgkin type
  • Calcification/necrosis is seen in post-treatment cases51
zoom view
Fig. 28: Axial CT image showing tuberculoma in the temporal lobe.
zoom view
Fig. 29: Axial CECT image shows multiple conglomerate ring enhancing lesions with perilesional edema in the right temporal lobe and basal ganglia suggestive of tuberculomas.
  • Metastatic involvement of the CNS is usually seen as a leptomeningeal involvement or focal, nodular. Enhancing, intra-axial mass
  • Perineural tumors are also common sites of metastatic lymphoma
Leukemia
It is seen as an extra-axial, enhancing, lobulated dural-based masses
These are commonly seen in the pediatric age group and the most common leukemia to metastasize to brain is acute myeloblastic leukemia (AML)52
Menin- gioma (Figs. 30A and B)
  • It is seen as a round, iso- to hyperdense, (Fig. 30) moderate to intensely enhancing, extra-axial mass with dural tail
  • Edema in the adjacent brain parenchyma is common with larger lesions
  • Sometimes, it is present as a calcified, minimally enhancing mass or as a small, dural-based, enhancing plaque (focal dural thickening)
  • Hyperostosis in the adjacent bony calvaria are highly suggestive
  • Atypical varieties may show ring enhancement and bone erosion
Most common sites are the falx cerebri, cerebral convexities, sphenoidal ridge, and the tentorium
Medullo-blastoma
  • It is seen as a midline, vermian, predominantly solid mass arising from the roof of the fourth ventricle that is hyperdense on noncontrast images and shows moderate postcontrast enhancement. Calcification is seen in up to 50% cases
  • CNS dissemination is seen at the time of presentation in up to 50% cases. There- fore, image the entire neuraxis
  • It is usually seen before 15 years of age
  • The features are more atypical if the tumor is seen in adults
  • If tentorial calcification present, rule out Gorlin-Goltz syndrome.53
zoom view
Figs. 30A and B: Axial CT images showing tentorial meningioma on right side.
  • Predominantly cystic mass; no postcontrast enhancement and isoattenuating on NECT may be seen in atypical cases
  • The tumor can arise in the cerebellum
Choroid plexus papilloma
  • It is seen as a cauliflower like, solid, moderate to intensely but heterogeneously enhancing mass arising in the ventricular system usually associated with hydrocephalus due to CSF over-production
  • Calcification is seen in up to one-quarter of the cases
  • CSF dissemination is common
  • The most common site is the trigone of the lateral ventricle
  • In children, it is commoner in the supratentorium and in adults in the infratentorium54
Choroid plexus carcinoma
  • CT findings are similar to choroid plexus papilloma
  • Parenchymal and CSF dissemination is seen
  • The most common age group is under 5 years
  • Differentiation from papilloma is not possible on imaging
Astro-cytoma (Figs. 31A and B)
  • Pilocytic type is seen as a round, hypo- to isoattenuating, nonenhancing tumor with a heterogeneously enhancing mural nodule
  • Edema is usually absent
  • Low-grade glioma is seen as focal or diffuse hypodense, non or minimally enhancing mass in the cerebral white matter with or without involvement of the gray matter
  • Hemorrhage, necrosis, and edema are uncommon but calcification may be seen in up to 20% cases
  • Anaplastic glioma or glioblastoma multiforme are seen as ill-defined, inhomogeneous, usually nodular, ring enhancing masses in the cerebral white matter with massive edema and mass effect
  • Hemorrhage and necrosis are common as opposed to calcification, which is uncommon.
  • CNS dissemination is common
  • Pilocytic type is seen usually in childhood
  • Common site is around the third and fourth ventricle
  • Low-grade glioma usually in children and young adults
  • Presence of the lesion in the corpus callosum and its spread on either of midline is more suggestive of glioblastoma multiforme55
zoom view
Figs. 31A and B: Axial CT images showing cystic glioma.
Gliomato-sis cerebri
It is seen as a diffusely, infiltrating, non-enhancing, white matter lesion causing cerebral enlargement but with preservation of the overall brain morphology
The common sites include optic nerves, corpus callosum, fornices, and cerebral ped-uncles
Brainstem glioma (Fig. 32)
They are usually seen as enlargement of the brainstem due to their infiltrative quality and appear as hypodense on noncontrast images and may show variable enhancement
  • It may encase the basilar artery
  • They are commonly seen in children and may be exophytic
Subepen-dymal giant cell astro-cytoma (Fig. 33)
It is seen as a cystic, partially calcified, heterogeneously enhancing mass at the foramen of Monro with features of obstructive hydrocephalus
  • It occurs with tuberous sclerosis
  • Other stigmata of tuberous sclerosis may be suggestive of the diagnosis56
zoom view
Fig. 32: Axial CECT image in a patient with brainstem glioma shows expansion of the brainstem with encasement of the basilar artery.
zoom view
Fig. 33: Subependymal giant cell astrocytoma—heterogeneous enhancing mass lesion seen in the region of foramen of Monro in this patient of tuberous sclerosis.
Oligoden-droglioma (Fig. 34)
  • It is usually seen as a partially calcified, iso- to hyperdense, mild-to-moderately enhancing mass in the white matter usually of the frontal lobe with extension into the gray matter
  • Cystic degeneration is common but hemorrhage, necrosis, and edema are uncommon
  • Overlying skull may show signs of pressure erosions
  • It is seen in the middle-aged adults
  • Allelic deletion of 1p and 19q is favorable for chemotherapy57
Ependy-moma
  • It is characterized by heterogeneous, lobulated mass with cyst and calcification with variable postcontrast enhancement
  • It is most commonly seen arising from the floor of the fourth ventricle
  • Plastic growth: Squeezes out laterally from foramen of Luschka and posteriorly from foramen of Magendie.
It is extraventricular in location when supratentorial while intraventricular in location when infratentorial
Subepen-dymoma
It is seen as a well-defined, homogeneously, iso- to hypodense, nonenhancing or minimally enhancing mass usually in the region of the frontal horns and the inferior aspect of the fourth ventricle
It is a rare tumor seen in the middle-aged and the elderly
zoom view
Fig. 34: A partially calcified oligodendroglioma seen in right perisylvian region.
58
Ganglio-glioma
  • It is seen as a well-defined, cystic lesion with iso- to hypodense mural nodule that may often be calcified. Enhancement is variable
  • They are usually located peripherally and so may be associated with scalloping of the over-lying calvaria
They are commonly seen in pediatric age group and most commonly in the supratentorium in the temporal lobe
Hemangio-pericytoma (Fig. 35)
  • They are seen as heterogeneous density lesions with cystic areas on noncontrast images
  • Postcontrast images show intense heterogeneous enhancement. Vascular channels may be seen within the lesion
  • Extra-axial signs may be suggestive of the lesion
They have a strong propensity for extraneural meta-stases to bone, both local and distant
zoom view
Fig. 35: Intensely enhancing vascular mass lesion seen along posterior falx—hemangiopericytoma.
59
Pineal cell tumors
It is seen as a well-defined, hyperdense strongly enhancing mass with presence of calcification in 80% cases. Pineal tumors show blast-type calcification.
They account for two-thirds of the pineal tumors and usually occur in second decade
Germ cell tumors
Germi-noma, teratoma (Fig. 36)
Synchronous lesions in the suprasellar region are also present. Appears to engulf calcification.
Germinoma are eight times more common in males
Parenchy-mal cell tumors pineo-cytoma pineo-blastoma
  • They appear as heterogeneous masses containing cysts, calcification, and fat and showing minimal enhancement
  • They appear as a well-defined, partially calcified cystic mass
  • It may resemble a medulloblastoma on imaging
  • Distinction from pineal cyst is not possible on imaging
  • It is a primitive neuroectodermal tumor (PNET) tumor
zoom view
Fig. 36: Well-defined enhancing mass lesion seen arising from the pineal gland.
60
Neural tumors
  • Schwannoma is seen as well-defined, homogeneous, Hypo- to isodense lesions with moderate-to-intense homogeneous postcontrast enhancement. Cystic degeneration in the larger lesion is common resulting in heterogeneous postcontrast enhancement. Calcification and hemorrhage are rare
  • Neurofibroma is seen as a poorly delineated, infiltrative mass lesion, isodense with muscle with variable contrast enhancement. Erosion and enlargement of the neural foramina of the affected nerve is common
  • Schwannoma is seen in middle-aged females and can involve any cranial nerve except Ist and IInd
  • It commonly involves VIIIth cranial nerve and seen as cerebellopontine angle (CPA) mass. When it involves the V nerve, it has to be differentiated from neurofibroma
  • Association is seen with neurofibromatosis-2 (NF-2), when they are multifocal and seen at an early age
  • Neurofibroma is associated with NF-1 and is seen at all ages with no sex predilection
  • It commonly involves the VIth cranial nerve
Pituitary adenoma (Figs. 37A and B)
  • Microadenoma may cause slight contour asymmetry of the pituitary gland, and is visualized as a hypodense lesion on CECT due to lesser enhancement relative to the normal parenchyma
  • Macroadenoma appears as well-defined, isodense sellar mass showing moderate homogeneous enhancement and displacing the part of normal pituitary gland and its infundibulum. It balloons the sella causing pressure erosion of the surrounding bone. Suprasellar extension gives a typical figure-of-eight appearance to the lesion
  • Microadenoma measures less than 10 mm in size
  • It is the most common intrasellar tumor in adults
  • Though rare in children, most lesions occur in adolescent girls
  • Cystic adenoma is indistinguishable from other cystic lesions of the sella61
zoom view
Figs. 37A and B: Coronal and sagittal CT images showing pituitary macroadenoma.
  • Calcification is rare, however, hemorrhage is seen within the lesion which imparts an inhomo- geneously hyperdense appearance to the tumor
Cranio-pharyn-gioma (Fig. 38)
  • It appears as heterogeneous, lobulated, suprasellar mass showing variable enhancement
  • Calcification is common in the lesion either ring-like or globular
  • Erosion of the posterior clinoid process is common
  • It commonly occurs in children and middle-aged adults
  • Most lesions have a sellar component as well62
zoom view
Fig. 38: Craniopharyngioma—a suprasellar cystic mass lesion with calcification.
Metastases
  • Parenchymal lesions are seen usually at the gray white matter interface as well-defined lesions of variable attenuation and edema that is out of proportion to the size of the lesion. Postcontrast images show variable enhancement including thick, nodular, ring-like appearance
  • Leptomeningeal lesions are seen as focal or diffuse, enhancing, nodular lesions in the sulcal and fissural location
  • Dural metastases as an isolated entity are rare and can be missed on CT
  • The common sites of the primary tumor metastasizing to brain include lung, breast, melanoma, gastrointestinal, genitourinary tract (GUT), etc.
  • Hemorrhage may be seen within the lesions in case of breast, renal cell carcinoma, and choriocarcinoma
  • Leptomeningeal variety is commonly seen with highly malignant astrocytoma63
zoom view
Figs. 39A and B: Axial CT images showing bony lytic metastases with extradural soft tissue mass.
  • Calvarial metastases have variable appearance ranging from small lytic areas to large areas of bony destruction associated with enhancing extradural, soft tissue mass (Figs. 39A and B)
Metachro-matic leukody-strophy (MLD)
  • Symmetric hypodensity in the deep white matter with relative sparing of the subcortical U-fibers is characteristic
  • The anterior fibers are first and more severely affected
Cerebellum is often atrophic
Krabbe disease/globoid cell leukodys-trophy (GLD)
  • Symmetric hypodensity in the deep white matter with relative sparing of the subcortical U-fibers is characteristic
  • The parieto-occipital lobes are the first to be involved
  • The brain is small and atrophic
  • Cerebellum is relatively spared or less severely affected64
Adreno-leukodys- trophy (ALD)
  • Large, symmetric hypodensity in the parieto- occipital or peritrigonal region with sparing of the subcortical white matter in the early stages is typical
  • Postcontrast images show rim enhancement at the advancing edge of the demyelination surrounded by peripheral edema in the adjacent brain
  • Predominantly unilateral or frontal involvement is seen in atypical cases
  • Degenerative changes are seen in the internal capsule, brainstem, and cerebellum
Pelizaeus–Merz-bacher disease (PMD)
  • It is characterized by patchy hypodensity in the deep white matter with relative sparing of the internal capsule and subcortical fibers
  • In the less common form, there is nonspecific diffuse hypodensity involving all the white matter
  • The cortex is intact
  • Atrophic changes are seen in the cerebrum and cerebellum
  • Enlarged ventricular system is usually present
Alexander disease
  • There is diffuse, symmetric, hypodensity involving the frontal white matter and the basal ganglia
  • Postcontrast images may show patchy nodular or discoid enhancement within the hypodensity
There is increased volume of the brain in the affected region with effacement of the sulcal spaces and other subarachnoid spaces
Canavan disease
  • Preferential involvement of the subcortical fibers is the hallmark
Thalami and basal ganglia may be involved in severe cases65
  • But in severe cases, there is diffuse hypodensity of the white matter of the entire brain with sparing of only the internal capsule
Amino-aciduria including phenyl-ketonuria (PKU)
These are characterized by diffuse, nonenhancing, periventricular hypodensity with relative sparing of the subcortical fibers
Tay-Sachs disease
  • Basal ganglia show symmetrical, homogeneous, hyperdensity
  • Early stages show enlarged caudate nuclei protruding into the lateral ventricles
  • Late stages are characterized by severe cortical atrophy
It is a type of lipidosis
Mucopoly-sacchari-doses
The findings that characterize these conditions include thickened dura, perivascular hypodensities, and varying degree of cortical atrophy
The conditions are indistinguishable from each other only on the basis of the brain findings
Mucolipi-dosis, fucosidosis and glycogen storage diseases
These are characterized by thinning of the cortex with nonspecific white matter changes in the form of nonspecific hypodensity, gliosis, and atrophy
It is not possible to distinguish these diseases on CT imaging66
Leigh disease
  • It is characterized by nonenhancing, hypodensity in the periaqueductal, subependymal, and tegmental gray matter
  • Periventricular white matter also shows similar hypodensity
It is also known as subacute necrotizing encephalopathy
MELAS/MERRF syndrome
  • It is characterized by the nonspecific, gray, and white matter cerebral infarcts affecting any part of the brain but the occipital lobes are the sites of predilection
  • Multifocal venous occlusion are also associated
It falls into the category of mitochondrial encephalopathy
Zellweger syndrome
It is characterized by heterotopias, pachygyria and polymicrogyria with a generalized reduction in the white matter thickness
It is included in the peroxisomal disorders
Multiple sclerosis
  • It is characterized by multiple, iso- to hypodense, ovoid lesions in the periventricular white matter arranged perpendicular to the long axis of the lateral ventricles showing variable degree and patterns (ring or nodular) of postcontrast enhancement
  • Callososeptal interface is also a common site of involvement with periventricular extension of the lesions into the deep white matter referred to as the Dawson’ finger
  • The disease is commonly seen in young females
  • Brainstem and cerebellum involvement is commoner in children than adults67
Vascular disease (arterio-sclerosis, vasculitis, embolism, hypoxic-ischemic encepha-lopathy)
  • It is characterized by a spectrum of white matter changes ranging from nonspecific, nonenhancing hypodensity to frank infarcts with gliosis and encephalomalacia in late stages with variable involvement of the gray matter
  • The site of involvement depends upon the age
  • In preterm infants, bilateral periventricular white matter involvement is typical with resultant loss of white matter and atrophy in late stages
  • In term infants, the cortical and subcortical white matter are the sites of involvement; deep gray matter nuclei are also commonly involved
  • In children and adults, gray matter is more commonly affected with cortical loss
  • In the elderly, the periventricular white matter is the usual site of lesions
Toxic demyeli- nation (alcohol, drugs and chemicals, osmotic demye-lination)
  • These are characterized by nonspecific white matter hypodensity at variable location depending upon the cause of insult
  • In osmotic demyelination, the usual site is pons
Common agents associated with such type of lesions include cyclosporine, metho- trexate, 5-fluorouracil, hydrocarbons, mercury, lead, etc.68
  • In alcoholism, pons (osmotic cause) and corpus callosum (Marchiafava-Bignami disease) are the common sites
  • In chronic alcoholism associated with Wernicke encephalopathy, both white and gray matter are involved. Periventricular region, midbrain, Tectum, and thalami are commonly involved
Acute dissemi-nated encephali-tis (ADEM)
It is characterized by multifocal, bilateral, non- enhancing, hypodense lesions typically involving the subcortical white matter, but deep white matter, diseases, brainstem, and cerebellum may also be involved
  • The disease occurs following childhood exanthematous RTI, and vaccination against rabies, DPT, etc.
  • The lesions usually appear 1–2 weeks after the contact with the inciting agent
Subacute scle-rosing panence-phalitis
  • It is characterized by hypodense, nonenhancing foci in the subcortical and deep white matter progressing to gliosis
  • Gray matter involvement is common especially the basal ganglia
  • Generalized atrophy of the brain is common
It occurs several years after the measles infection69
 
MISCELLANEOUS LESIONS OF THE BRAIN
 
Intraparenchymal Hemorrhagic Lesions in Brain
Hemorrhagic lesions in brain can be broadly categorized into:
  • Nontraumatic:
    • Hypertension
    • Aneurysm and vascular malformation (AVM, cavernous angioma)
    • Perinatal hemorrhage
    • Hemorrhagic infarction (reperfusion or venous)
    • Neoplastic
    • Miscellaneous:
      • Amyloid angiopathy
      • Coagulopathies and blood dyscrasias
      • Drug abuse
      • Eclampsia
      • Infections (vasculitis, encephalitis, abscess, endocarditis with septic emboli)
  • Traumatic:
    • Diffuse axonal injury
    • Cortical contusions
    • Deep cerebral and brainstem lesions.
 
CT Findings of Hemorrhage
  • Acute hemorrhage (0–72 hours): It appears hyperdense to human brain. Unretracted semiliquid clot appears hypodense within the hyperdense acute hematoma, giving rise to the so-called swirl sign.
  • Subacute hemorrhage (4–14 days): Subacute hemorrhage becomes virtually isodense with the adjacent brain parenchyma. It may sometimes show a peripheral postcontrast enhancement.
  • Chronic hemorrhage (>2 weeks): It appears hypodense to the adjacent brain. High attenuation within chronic hematomas is usually secondary to the rebleeding. Rim enhancement around a resolving hematoma typically appears within a few days and disappears between 2 and 6 months.70
    zoom view
    Fig. 40: Axial CT image showing hypertensive acute hematoma in the left cerebral hemisphere.
    A target sign on postcontrast images can be seen if rehemorrhage takes place within an organizing hematoma; if rebleeding occurs outside an organized hematoma, it can resemble a tumoral hemorrhage.
 
Hypertensive ICH
  • Hypertensive intracerebral hemorrhages (HICH) are the most common nontraumatic cause in adults (Fig. 40)
  • Most are associated with systemic hypertension and in some, ruptured microaneurysms are implicated
  • Common location include putamen/external capsule followed by thalamus, pons, cerebellum, and subcortical white matter in the decreasing order of frequency.
 
Aneurysm and Vascular Malformation (AVM, Cavernous Angioma)
Hypertensive intracerebral hemorrhage (Figs. 41A to C):
  • Ruptured aneurysms are associated with either intraparen-chymal or subarachnoid hemorrhage71
zoom view
Figs. 41A to C: Axial and sagittal CT images showing a large AV malformation with an aneurysm and hematoma.
(AV: aneurysm and vascular)
  • Acute SAH is characterized by hyperdensity in the subarachnoid spaces (basal cisterns, fissures, sulci) (Figs. 42A and B)
  • Although SAH tends to be diffuse; more focal cisternal or parenchymal hematomas can be due to ruptured aneurysms and are helpful in localizing the bleeding source
  • Blood in the Sylvian fissure—aneurysm on the I/L ICA.
  • Focal interhemispheric blood—Anterior com artery aneurysm
  • Blood in the fourth ventricle—Posteroinferior cerebellar artery aneurysm
  • ICH secondary to AVM are usually seen in children or normotensive young adults
  • AVM are usually associated with gliotic and encephalomalacic changes72
zoom view
Fig. 42: Axial CT images showing posterior interhemispheric acute SDH and SAH in the right frontal lobe.
(CT: computed tomography; SAH: subarachnoid hemorrhage; SDH: subdural hematoma)
  • Cavernous angiomas typically have a popcorn-like appearance with calcification and mixed signal foci inside a hemosiderin ring.
 
Perinatal Hemorrhage
  • In term infants, it is usually the result of hypoxic-ischemic insult
  • Areas of hemorrhage are typically seen in the posterolateral lentiform nuclei and ventral thalamus
  • Although the cortex can be involved in profound asphyxia, it is relatively spared compared to the deep gray matter
  • In premature infants, germinal matrix hemorrhage (GMH) is the most common form of ICH followed by intraventricular and intraparenchymal hemorrhage that are usually secondary to the former.
  • Germinal matrix hemorrhage is divided into four grades:
    • Grade I: Hemorrhage confined to one or both germinal matrices73
      zoom view
      Figs. 43A and B: Axial CT images showing hemorrhage in left lateral ventricle in an adult patient.
    • Grade II: Hemorrhage ruptured into a normal-sized ventricle
    • Grade III: Intraventricular hemorrhage with hydrocephalus (Figs. 43A and B)
    • Grade IV: Hemorrhagic extension into the adjacent hemispheric white matter.
 
Hemorrhagic Infarction (Reperfusion or Venous)
  • Hemorrhagic infarction is usually the result of lysis of embolus/opening of collaterals/restoration of normal blood pressure following hypotension/hypertension/anticoagulation causing extravasation in reperfused ischemic brain
  • It is seen in approximately 6% of brain infarcts and is usually at the corticomedullary junction
  • CT will show the hyperdensity within a previously imaged hypodense acute ischemic infarct
  • Venous infarctions are usually hemorrhagic, bilateral, and occur primarily in the white matter and are most often associated with cortical vein and dural sinus thrombosis
  • CT demonstrates patchy foci of edema and petechial hemorrhage with or without signs of dural sinus thrombosis.74
 
Neoplastic
  • Common brain tumors that are commonly associated with hemorrhage include: pituitary adenomas, high-grade gliomas, PNET, epidermoid and metastases from bronchogenic, and renal, chorio- and melanocarcinoma.
  • Points of benign versus malignant hemorrhage:
    • There is no absolute criteria
    • Tumors are complex and heterogeneous
    • Benign lesions usually have a complete hemosiderin ring
    • Nonhemorrhagic areas of the tumor enhance on postcontrast images
    • Hemorrhage evolution is disordered or delayed in tumoral lesions in contrast to an orderly evolution seen in benign hemorrhage
    • Edema/mass effect resolve with resolution of hematoma in benign lesions while it will persist with malignant lesions
    • Hemorrhagic metastatic deposits will be multifocal.
 
Amyloid Angiopathy
  • This is probably the most common cause of recurrent bleeding in normotensive elderly and the incidence increases with advancing age
  • Hemorrhages are characteristically multiple, spare the basal ganglia and brainstem, and are located at the corticomedullary junction
  • Computed tomography findings of multiple peripherally located hemorrhages of different ages in an elderly normotensive patient strongly suggests the cause as amyloid angiopathy.
 
Inflammatory Disease and Vasculitis
  • Hemorrhage in immunocompetent persons is uncommon, but immunocompromised individuals are at increased risk of developing hemorrhage in infectious lesions75
  • Such lesions include infective endocarditis with septic emboli, fungal vasculitis, and necrotizing lesions as herpes encephalitis
  • Aspergillosis and other fungal infections may directly invade the vessel wall and cause thrombosis, Hemorrhage, or cerebral infarction
  • Type II herpes simplex encephalitis is the most prone to develop hemorrhage especially in neonatal herpes.
 
Drug Abuse
  • Drugs like cocaine can induce a hypertensive episode in which case the location of ICH is similar to that in hypertensive ICH
  • Cocaine also promotes arterial and dural sinus thrombosis producing venous infarction and ischemic infarction with subsequent hemorrhage
  • Vasculitis with hemorrhage is seen commonly with amphetamines and phenylpropanolamine and less commonly with cocaine.
 
Blood Dyscrasias and Coagulopathies
  • Common causes of noniatrogenic coagulopathy include vitamin K deficiency, hepatocellular disease, antibodies that react to clotting factors, and disseminated intravascular coagulation (DIC). Iatrogenic causes include mainly anticoagulants as heparin, warfarin, thrombolytic agents as streptokinase, antiplatelet agents as aspirin, etc.
  • Imaging findings in most coagulopathies are similar.
  • Although bleeding can occur at any location, the most common site is supratentorial and intraparenchymal with multifocal lesions with fluid—fluid levels within the hematomas.
 
Eclampsia
  • Posterior circulation is particularly prone
  • Lesions are commonly seen at corticomedullary junction and within external capsule and basal ganglia76
  • The occipital lobes are a frequent location of cortical and subcortical lesions
  • CT scans will reveal multiple hypoattenuating foci or hemorrhages in the subcortical white matter or basal ganglia.
 
Diffuse Axonal Injury
  • Diffuse axonal injury (DAI) is most common form of the intra-axial primary traumatic lesion
  • It tends to occur in the lobar white matter, corpus callosum, and dorsolateral aspect of the brainstem
  • Nearly two-thirds are seen at the gray white matter junction, most often in the frontotemporal region, splenium and posterior body of the corpus callosum
  • Early CT scans may be unremarkable. Delayed scans in acute DAI may reveal petechial hemorrhages in the location mentioned above.
 
Cortical Contusions
  • It is the second most common form of the intra-axial primary traumatic lesion (Figs. 44A and B)
  • Majority involve the temporal lobes followed by the frontal lobes and other sites as the cerebellar hemispheres
  • Early findings include patchy, ill-defined, frontal or temporal hypodense lesions that may be mixed with smaller hyperdense foci of petechial hemorrhages
  • Delayed scans at 24–48 hours may reveal hemorrhages developing in the previously hypodense regions.
 
Deep Cerebral and Brainstem Lesions
  • Computed tomography is often normal in these patients
  • Petechial hemorrhages are sometimes seen in the dorsolateral brainstem, periaqueductal region, and deep gray matter nuclei.77
zoom view
Figs. 44A and B: Axial CT images showing cortical contusions.
 
Conditions Primarily Presenting as Cerebral Atrophy (Table 14)
  • Alzheimer's disease
  • Pick's disease
  • Vascular dementia
  • Extrapyramidal disorders
  • Subcortical dementia
  • Dyke-Davidoff-Masson syndrome.
 
Conditions Primarily Presenting as Cerebellar Atrophy (Table 14)
  • Diffuse brain atrophy in the elderly
  • Secondary to previous infarct/trauma
  • Phenytoin toxicity (involves mainly the cerebellar hemispheres)
  • Ethanol toxicity (involves mainly the cerebellar vermis)
  • Olivopontocerebellar degeneration
  • Ataxia-telangiectasia syndrome78
  • Paraneoplastic cause (secondary to oat cell carcinoma of the lung)
  • Postradiotherapy.
 
Effaced Basal Cisterns
Enhancing:
  • Meningitis especially tuberculous
  • Leptomeningeal carcinomatosis (usually nodular enhancement)
  • Sarcoidosis (thickened leptomeninges).
Nonenhancing:
  • Subarachnoid hemorrhage (isodense to hyperdense cisterns)
  • Cerebral edema
  • Diffuse axonal injury
  • Hydrocephalus
  • Racemose NCC (cystic, septated appearance of cisterns).
TABLE 14   Differentiating features of common conditions presenting as cerebral and cerebellar atrophy.
Types
Differentiating features
Comments
Alzheimer's disease
  • It is characterized by diffusely enlarged ventricles especially the temporal horns
  • Cortical sulci are also enlarged especially in the anterior temporal lobes and the hippocampal region
  • Fissures are increased in size especially the choroidal, hippocampal, and Sylvian fissures
  • It is the most common acquired neurodegenerative disorder
  • There is decrease in cortical thickness especially in the temporal lobes79
Pick's disease
  • It is characterized by asymmetric lobar atrophy involving the frontal and temporal lobes
  • Parietal and occipital lobes are spared
  • There is decrease in cortical thickness in the frontal and temporal lobes
  • Ventricular system is enlarged
Vascular dementia
Multi-infarct dementia is characterized by multifocal infarcts involving both gray and white matter (cortical and subcortical region), enlarged ventricles, and sulci
It is the second most common acquired neurodegenerative disorder
Dyke-Davidoff-Masson syndrome
  • It is characterized by cerebral hemiatrophy with reduced cortical and white matter thick- ness, enlarged ventricle, and sulci on the side of affection (Table 14)
  • There is associated thickening of the calvaria, enlargement of the sinuses, and elevation of the petrous bone on the side of affection
It is usually congenital but may be acquired following massive large infarction
Huntington's disease
  • It is characterized by cortical and subcortical atrophy
  • There is striking atrophy of the basal ganglia especially caudate nucleus; cerebellar and brainstem atrophy may also be seen
  • There is focal dilatation of the frontal horns of lateral ventricle with convex lateral border
It is usually seen in fourth or fifth decade80
Fahr's disease
It is characterized by bilateral extensive calci- fication in the basal ganglia, dentate nuclei, centrum semiovale, and subcortical white matter
It is a hereditary disorder
Wilson's disease
It is characterized by bilateral putaminal, hypodense lesions associated with mild generalized atrophy
It is associated with hepatic cirrhosis and degenerative changes in the brain secondary to deposition of the copper
Ataxia-telangiec-tasia syndrome
  • It is characterized by cortical cerebellar atrophy with dilated fourth ventricle and cerebellar folia
  • Cerebellar infarct and hemorrhage are frequently associated
This syndrome is characterized by telangiectasia of the skin and eyes; cerebellar ataxia, sinusitis and pulmonary infections; immunodeficiencies; and increased susceptibility to malignancies
Olivoponto-cerebellar atrophy
  • It is characterized by focal or diffuse atrophy of the cerebellum, pons, and inferior olives
  • The cerebellum is shrunken with dilated fourth ventricle, folia, and cisterns (supracerebellar and cerebellopontine cisterns)
Basal ganglia and spinal cord may be involved81
 
DIFFERENTIAL DIAGNOSIS OF CEREBELLOPONTINE ANGLE MASSES (TABLE 15)
TABLE 15   Differential diagnosis of cerebellopontine angle masses.
Diseases
CT findings
Comments
Acoustic Schwannoma
  • Isodense mass over the internal auditory canal forming an acute angle with the temporal bone like an ice cream cone.
  • Homogeneous enhancement. May contain necrosis, rarely calcified
Most common CPA mass (60–75%), seen in patients between 20–50 years. Arises from the glial—Schwann cell interface of vestibular nerve. Schwannoma bilateral in neurofibromatosis-2.
Meningioma
Isodense or hyperdense, strongly and uniformly enhancing mass. Broad dural base, obtuse angle with the temporal bone. Not centered over the IAC. IAC is not widened. Hyperostosis of the adjacent temporal bone and/or calcification may occur
Second most common CPA mass (10%). Typical age 30–60 years.
Epidermoid (congenital cholestea-toma)
Homogeneously hypodense, irregular, or lobulated nonenhancing CPA mass
4–5% of CPA mass lesions. 20–50 years. Arises from intracranial or intraosseous ectoderm inclusions. Found in the CPA as well as in the petrous temporal bone. Contains cholesterol or keratin debris.82
Nonacoustic Schwan-noma
Isodense homogeneously enhancing mass associated with one of the cranial nerves, most often 7th cranial nerve
5% of CPA mass lesions.
Paragan-glioma (glomus jugulare)
Isodense, strongly enhancing mass with erosion and enlargement of the jugulare foramen
2–10% of CPA masses 40–60 years
Vertebro-basilar dolichoect-asia
Tubular, hyperdense, strongly enhancing, often calcified tubular mass
3–5% of CPA masses. An atherosclerotic or degenerative lesion seen in patients over 50 years.
Aneurysm
3–5 mm or larger aneurysms may be seen on CT as oval or round enhancing vascular lesions
1–2% of CPA masses. Seen in between 20 years and 50 years of age. Berry aneurysms originate from the vertebral artery, superior cerebellar artery, or posterior inferior cerebellar artery
Arteriove-nous malfor-mation
Serpiginous isointense or hyperintense foci with strong enhancement following administration of contrast material calcification may be present
1% of CPA masses. Typically seen in between 20 years and 40 years of age
Glioma of brainstem or cerebellum
If solid hypodense, often 50% cystic. Solid portions enhance calcification in 20%
More common in cerebellum than brainstem. More common in children than in adults. May be associated with severe hydrocephalus before becoming symptomatic83
Metastasis
Extra-axial: destructive mass centered in bone. Intra-axial: enhancing mass in the brainstem with an exophytic component extending into the CPA
Originates in the clivus or temporal bone adjacent to the CPA
Heman-gioma
Spherical or nodular sharply delineated hyperdense mass which shows uniform, strong enhancement. Calcification may be present
Rare, less than 1% of CPA lesions. May be difficult to distinguish from meningioma
Lipoma chordoma
  • Low-density, nonenhancing lesion
  • Large isodense or hyperdense destructive clival and skull base mass typically midline. May contain calcification. Minimal enhancement
Rare, less than 1% of CPA lesions 1% of CPA masses, in older adults. Originates from notochordal remnants in the clivus.
Arachnoid cyst
Well-delineated smoothly marginated mass isodense with CSF. May erode adjacent bone
Rare. Split or duplicated arachnoid membranes containing CSF. Dandy-Walker cyst of fourth ventricle can involve the CPA
Inflamma-tory lesions
Diffuse enhancement of leptomeninges, including both CPA cisterns. Communicating hydrocephalus due to fibrosis of the CPA cisterns
Bacterial meningitis, tuberculosis cause meningeal enhancement. Mass-like effect in cysticercosis, sarcoidosis, and histiocytosis
(CPA: cerebellopontine angle; CSF: cerebrospinal fluid; IAC: internal auditory canal)
84
 
DIFFERENTIAL DIAGNOSIS OF INFRATENTORIAL LESIONS (TABLE 16)
TABLE 16   Differential diagnosis of infratentorial lesions.
Diseases
CT findings
Comments
Brainstem glioma
Isodense, hypodense, or mixed with partial contrast enhancement in 50%. Cysts occur in 20%. Encasement of basilar artery seen in 45%
In children, 25% of gliomas occur in brainstem; in adults only 2.5%. Hemorrhage, no enhancement and change from nonenhancing to enhancing tend to indicate aggressive nature of tumor
Astrocytoma of the cerebellum
Hypodense, 50% solid, 50% cystic. Calcification in 20%. Solid lesions enhance well. Obstructive hydrocephalus is common in vermis of fourth ventricle tumors
Common posterior fossa neoplasm in children
Medullobla-stoma
Cerebellar vermis; denser than normal cerebellum on unenhanced scans. Enhances well unless necrotic. Hydrocephalus common. Subarachnoid metastatic spread is common as “icing on the cake”
Common posterior fossa tumor in the children
Ependy-moma
An inhomogeneous mass in the fourth ventricle. 50% contain small flecks of calcium. Enhances homogeneously or heterogeneously. Hydro- cephalus is common
Most often in the first decade. Tendency to hemorrhage.85
Choroid plexus papilloma/carcinoma
Slightly hyperdense fourth ventricular mass, may calcify. Homogeneous contrast enhancement, hydrocephalus common. Carcinomas occur in infancy. Rare but often aggressive, often necrotic, and may invade the brain
More common in the lateral ventricle than in the fourth ventricle
Hemangio- blastoma
  • Either solid or cystic with a mural tumor nodule, occasionally multiple. Over 90% located in cerebellar hemispheres. Nearly always in contact with the leptomeninges at some point
  • Enhancement of the solid component is strong. Calcification is rare
8–12% of posterior fossa tumors. Common in 20–40 years. Rare in children.
Schwan-noma
Most common in the acoustic nerve and located in the cerebellopontine angle. Isodense and well enhancing unless necrotic
Associated with neurofibromatosis-2
Meningioma
Hyperdense (75%) or isodense (25%) in nonenhanced scans. Broad dural surface is common. Calcification seen in 15–20%. Adjacent hyperostosis and edema of the underlying brain are common. Strong enhancement is a rule
5–10% of meningiomas occur in the posterior fossa; either in the cerebellopontine angle clivus or foramen magnum86
Epidermoid
Hypodense (0–10 HU), round mass usually in the cerebellopontine angle, no enhancement, no surrounding edema
The most common intracerebral tumor. Hydrocephalus is usually absent
Dermoid
Midline thick-walled hypodense (negative HU) inhomogeneous mass with focal areas of fat. No contrast enhancement or edema
Rare pilosebaceous mass lined with skin appendages, most common in the posterior fossa and in the base of the brain. Hydrocephalus is rare
Teratoma
Contains fat, nonadipose tissue and calcification. No enhancement or edema.
Rare obstructive hydrocephalus, usually absent despite large mass
Lipoma
Fat-density nonenhancing lesion in the CPA or in the cerebellum. May contain ring or central fleck calcification and enhance. No edema
Rare obstructive hydrocephalus usually absent
Metastasis
Appearance is variable, including densely enhancing nodules with surrounded by edema; large inhomogeneously enhancing mass; or ring enhancing tumors with central necrosis
Most common cerebellar tumors in older patients
Lymphoma
Poorly defined solid hyperdense enhancing mass, usually near the fourth ventricle or cerebellar surface. Little or no peritumoral edema
May be multicentric, does not respect normal anatomic boundaries. Seen in immunocompromised patients87
Infarct
Low-density lesion appears 12–24 hours after ictus; subacute infarcts may enhance and may simulate a neoplasm
Due to artefacts, CT is poor in detecting cerebellar or brainstem infarcts. PICA infarcts are the most frequent and involve portions of the cerebellar hemispheres and brainstem
Hemorrhage
High attenuating lesion that may compress or obstruct the fourth ventricle and cause hydrocephalus
Hemorrhage into the cisterns may appear as thin hyperdense layers adjacent to the tentorium or cisterns
Arteriovenous malfor-mation
Rapidly and strongly enhancing tortuous structures, variable degree of mass effect may be indistinguishable in precontrast scans
Cyst-like lesions or calcification may represent previous hemorrhage
Multiple sclerosis
Large, fresh cerebellar and brainstem plaque may appear expansile, enhances and mimics a neoplasm
Gliosis
Single or multiple low-density, nonenhancing lesion in the cerebellar hemisphere
May be seen in neurofibromatosis type 188
 
DIFFERENTIAL DIAGNOSIS OF SUPRATENTORIAL MASS LESIONS (TABLE 17)
TABLE 17   Differential diagnosis of supratentorial mass lesions.
Diseases
CT findings
Comments
Astrocytoma
  • Low-grade astrocytoma: usually well-delineated low-density mass with little or no enhancement.
  • Some tumors may calcify. Juvenile pilocytic astrocytoma: sharply marginated isodense, hypodense or mixed mass around third/fourth ventricle (optic chiasm, hypothalamus, cerebellar vermis) cysts are frequent and contain an enhancing mural nodule. Anaplastic astrocytoma: less well-defined, often heterogeneous density showing greater mass effect and contrast enhancement
  • 25–30% of these are relatively benign, occurs usually between 20 years and 40 years in white matter. May become more malignant. Pilocytic astrocytoma is a sub- type of astrocytoma in children and young adults, often associated with neurofibromatosis. Rare in cerebral hemispheres. Most common in temporal lobes
  • 25–30% of astrocytomas, usually after 40 years of age
Glioblas-toma multiforme
Tumor in supratentorial white matter characterized by necrosis, hemorrhage, vasogenic edema, mass effect, heterogeneity, and substantial contrast enhancement
50% of astrocytomas; occurs in 50–70 years of age. Tends to be more malignant in older patients. Tumor cells diffuse widely outside the region of contrast enhancement89
Oligoden-droglioma
Typically low-density tumor with little enhancement. Most often in frontal lobe. Usually partly calcified
  • 5% of primary brain tumors.
  • Peak age: 35–40 years. 85% supratentorial. Nearly 50% astrocytic elements
Ependy-moma
Often periventricular/parenchymal. Calcified in 50%. Cysts are common, hemorrhage uncommon. May be indistinguishable from astrocytoma. Occurs at all ages
5% of intracranial tumors. 50% occur in children younger than 5 years. Two-thirds are infratentorial from the floor of fourth ventricle and often extend into CP angle or vallecula 15–20% of intracranial tumor
Menin-gioma
Rounded, sharply delineated (hypodense in 75%) in juxtadural location, parasagittal or convexity in 30–40%, sphenoid wing 15–20%. Intense enhancement in 90%. Calcification in 15–20%
  • Rare in children and adolescents. Arises from arachnoid lining cells and attached to dura
  • Hyperostosis is virtually pathognomonic. Histologic type variable
Ganglio-cytoma, ganglio-glioma, ganglio-neuroma
Well-circumscribed, low- or mixed-density lesion in frontal; or temporal, occipital lobe with little mass effect. Cysts are common (50%) calcification in one-third, enhancement is variable. Can erode the inner table of skull
Uncommon, 80% occur under the age of 30, occurs in third or fourth ventricle and cerebellum. Ganglioneuroma consists of preganglionic cells, ganglioglioma contains glial cells. Usually well-differentiated, may be anaplastic90
PNET
Grossly well-circumscribed hyperdense cerebral deep white matter mass with variable enhancement; cysts and calcification occur in 50% hemorrhage in 10%. Can be intraventricular
Less than 5% of supratentorial tumors, mostly seen in patients under 5 years of age. Highly malignant. Pathology is controversial.
Primary cerebral neuro- blastoma
Periventricular/intraventricular mass with little edema. Inhomogeneous enhancement. Calcification, cyst, and hemorrhage are common. Pattern is highly variable and nonspecific
Uncommon; 80% in patients under 10 years. Can be considered a subset of PNETs
Hemangio-blastoma
Solid/cystic mass with strong enhancement. Nearly always in contact with leptomeninges at some point. Rarely calcifies
Uncommon supratentorially. Occurs in young/middle-aged adults. Sporadic or associated with VHL. Over 90% occur in cerebellar hemispheres, medulla, or spinal cord. (10% of posterior fossa tumors)
Lymphoma
Isodense or hyperdense, poorly delineated, strongly enhancing mass, most often involving deep gray matter or corpus callosum; calcification is rare. In AIDS patients, may be necrotic and mimic infection (e.g. toxoplasmosis) with ring enhancement. 50% multiple
Traditionally rare. Incidence is rapidly growing with increase in AIDS patients. Occurs in immunocompromised patients, may be most common tumor in some locations. Primary CNS lymphomas are usually non-Hodgkin's type91
Langerhans cell histiocytosis
Focal isodense or hyperdense mass, most often in hypothalamic region. Strong and uniform enhancement
Previously known as histiocytosis X, brain parenchymal involvement is rare. May also involve leptomeninges and cranial nerves
Germinoma
Well-delineated suprasellar mass, may involve the infundibulum, rarely the thalamus, or basal ganglia. Hyperdense/calcified in 80%; strongly enhancing
Pineal gland is most common site (more than 50% of pineal tumors); other locations called “ectopic.” The ectopic are histologically identical to testicular seminoma and ovarian dysgerminoma. Striking male preponderance, up to 10:1
Teratoma
Heterogeneous pineal/suprasellar mass that may contain calcification, fat, cystic/solid component; minimal enhancement
Most common in pineal gland, lower incidence than germinomas but same age group (second decade) histology is variable
Pineal cyst
Small nonenhancing cystic lesion associated with pineal gland
Pineal cyst is relatively common but not always recognized on CT
Metastasis
Parenchymal mets are most commonly hypodense and enhance with contrast; most necrotic metastases are thick-walled and are surrounded by vasogenic edema
Metastases of lymphoma, osteosarcoma, melanoma, and choriocarcinoma are often hyperdense92
Lipoma
Midline; most often interhemispheric fat density mass. No enhancement but may show curvilinear calcification
Callosal lipomas, often associated with partial/complete agenesis of corpus callosum
Craniopharyn-gioma
Multilobulated sellar/suprasellar mass with variable enhancement. Contains cysts and calcification in 90%
Radiation necrosis
Deep focal hypodense mass near the irradiated tumor bed. May show an irregular ring of contrast enhancement.
Develops 9–24 months after radiation therapy. May be impossible to differentiate from residual/recurrent tumor
Cerebral infarction
From 12 hours to 48 hours: Poorly circumscribed, low attenuation subtle mass effect (sulcal effacement, ventricular displacement if large infarction). Enhancement uncommon. Hemorrhage in 5–10% as high density components. From 48 hours to 96 hours: Increasing mass effect. Focal area of triangular/wedge-shaped hypodensity involving the cortex and the underlying white matter down to ventricular surface
  • Early infarcts may become isodense and not detected unless CECT is performed.
  • Hyperosmolar contrast may be harmful in acute stroke.93
  • From 4 days to 7 days: Gyral contrast enhancement appears and may persist up to 8 weeks, hypodense infarct surrounded by low-density edema.
  • From 2 weeks to 8 weeks: Mass effect resolves, contrast enhancement may persist.
  • Old infarct: Well- delineated low-attenuation area, enlargement of adjacent sulci and ventricle. Calcification is rare
  • High-density atherosclerotic thrombus may be seen in the arterial lumen (dense MCA sign); shape of infarct corresponds to distribution of specific vessel and has characteristic peripheral enhancement; onset of symptoms is usually abrupt unlike glioma; most clinically detectable stroke is embolic and occur in MCA distribution. Thrombotic strokes are small and most often spare the cortex.
  • Post-traumatic infarctions occur due to vascular compression secondary to mass effect and are most often in PCA distribution
Pyogenic brain absces
Sequence from early and late cerebritis stage with focal enhancement. Central hypodense zone represents pus/necrotic tissue. Isodense uniformly enhancing ring represents fibrous capsule also, a peripheral low-density rim of white matter occurs representing reactive edema
C/F: Fever, leukocytosis, obstruction, extracranial infection, previous operation. Ring enhancement of gliomas may be irregular in thickness and may be impossible to differentiate from malignant gliomas
Hydatid cyst
Round, sharply marginated, smooth-walled hypodense mass.
Rare. Cysts in parenchyma tend to be large, multiple, thin-walled with no reactive edema or contrast enhancement94
Cerebritis
Irregular, poorly marginated hypodense edematous area in white matter/basal ganglia which may behave as a mass and result in effacement of sulci or ventricles. No enhancing capsule on unenhanced scans, but ring-like enhancement occurs
Usually bacterial/fungal infection. May progress to abscess in 10–14 days
Intracerebral hemorrhage (ICH)
Acute: Homogeneously dense well-defined lesion with round or oval configuration and moderate mass effect. Resolving (3–6 weeks): Hypodense region with thin uniform ring of enhancing tissue. May mimic a neoplasm
Causes: Head trauma, surgery, hypertension, rupture of vascular aneurysm, or malformation. Acute hemorrhage may be isodense in patients with anemia/coagulopathy
Epidural hematoma (EDH)
Biconvex high density extra-axial mass displacing adjacent interface between gray-white matter. Usually temporoparietal, less commonly frontal or occipital
Caused by traumatic laceration of meningeal arteries or disruption of dural sinuses/veins (especially in children); look for contralateral lesion of brain, subfalcine, or descending transtentorial herniation and signs of increased intracranial pressure, which are common associated findings95
Subdural hematoma (SDH)
Acute SDH: Crescentic high-density extra-axial hyperdense fluid collection. Typically frontoparietal, may extend into interhemispheric fissure and along falx displacement of adjacent interface between gray and white matter. Small subtemporal, subfrontal, and tentorial SDH are seen best on coronal scans. Subacute SDH (from few days to 3 weeks old): Isodense mass effect on adjacent interface between gray and white matter, underlying veins may be displaced as evident on contrast-enhanced scans. Underlying membrane may enhance chronic SDH (over 3 weeks old): Well-defined hypodense crescentic mass adjacent to inner table of skull. Thin marginal enhancement
Often associated with underlying brain injury (contusion, focal brain hematoma) commonly bilateral in infants. Interhemispheric SDH in child without SDH elsewhere should raise suspicion of nonaccidental trauma. Bilaterally symmetrical SDH may be difficult to detect when isodense with cerebral cortex. Look for indirect signs of mass effect using contrast enhancement. Repeat hemorrhage in previous chronic SDH may give a mixed-density lesion; contrast material may seep into hematoma and give fluid-fluid level (Fig. 45)96
zoom view
Fig. 45: Central nervous system tumors—summary.
(P: pinealoblastoma; G: glioma; M: meningioma; A: astrocytoma; MB: medulloblastoma; E: ependymoma; CP: choroid plexus papilloma; PA: pilocytic astrocytoma; AN: anaplastic ependymoma)
 
DIFFERENTIAL DIAGNOSIS OF WHITE MATTER DISEASES (TABLE 18)
TABLE 18   Differential diagnosis of white matter diseases.
Diseases
CT findings
Comments
Congenital demyelinating disorders
Alexander's disease (fibrinoid leuko-dystrophy)
Symmetric well-demarcated low-attenuation areas in deep white matter. Frontal lobes involved with extensive posterior extension. May enhance in caudate nuclei, fornices, forceps minor, optic radiation, and periventricular white matter
Rare, unknown biochemical defect, manifests within 1st year with macrocephaly and developmental retardation progresses through spastic quadriparesis and intellectual deterioration to death usually within 5 years. Diagnosis requires brain biopsy97
Canavan-van
Bogaert disease (spongiform leukodystro- phy)
Diffuse symmetric low-density changes throughout white matter, later ventriculomegaly and cerebral atrophy
Aspartoacylase deficiency, mitochondrial disorder that affects the CNS and skeletal muscle. AR, especially in Ashkenazi Jews. Onset before 10 months with neurological deterioration, blindness and death before 5 years
Krabbe's disease
Initially symmetric; hyperdense areas in the (thalami, caudate nuclei, cerebellum, and corona leukodystrophy). Later patchy periventricular; low-attenuation areas and diffuse white matter atrophy
Beta-galactosidase deficiency; autosomal recessive (AR) lysosomal disorder. Onset between 2 months and 6 months as retarded development, irritability, spasticity. Progresses through dementia, blindness, and quadriplegia to death within 1–3 years. Diagnosis is made through lymphocyte or skin fibroblast assay.
Pelizaeus- Merzbacher disease
CT may be normal. Later nonspecific white matter atrophy. Subtle periventricular white matter lucencies reported
X-linked recessive with lack of proteolipid apoprotein in white matter which leads to lack of myelination. Onset within the first few months of life. Nystagmus, abnormal eye movements, optic atrophy, slowly progressive pyramidal, dystonic, and cerebellar signs.98
Metachro-matic leukodys-trophy
Low-attenuation changes in periventricular white matter and centrum semiovale. No contrast-enhancement in brain atrophy
Automatic recessive lysosomal disorder with deficiency of arylsulfatase. A symptomatic, most common before the age of 3 but may present in juvenile, infant, or adult. In adults, mimics Alzheimer's disease, Pick's disease, and schizophrenia
Childhood adrenoleu-kodystrophy (ALD), most common
ALD
Symmetric low-attenuation changes in parieto-occipital white matter, which often show prominent rim enhancement, are characteristic. Changes progress from posterior to anterior and cause brain atrophy. Calcifications and mass effect may occur.
X-linked recessive, fatal peroxisomal disorder with accumulation of saturated very long chain fatty acids. Presents between 4 years and 8 years with behavioral changes, intellectual deterioration, and visual complaints
Disorders of AA metabolism
Propionic acidemia, methyl-malonic aciduria ornithine transcarbamylase deficiency
Nonenhancing foci of low-attenuation in white matter/diffuse low-density, white matter. Changes may reverse on effective treatment
Rare. AR. Delayed myelination and degeneration of white matter are characteristic and better seen on magnetic resonance imaging (MRI)99
Homocystei- nuria
Low-density lesions, which correspond to lacunar infarcts
Defect in cystathione synthetase leads to build up of homocysteine in plasma, urine, and CSF. Homocysteine is thrombogenic and may lead to multiple cerebral infarcts
Leucinosis (maple syrup urine disease)
Edema and later decreased attenuation of cerebral white matter, brainstem, cerebral peduncles, and dorsal parts of internal capsule
Disturbance of valine, leucine, and isoleucine metabolism. The patient's urine has characteristic smell. Deficiency of enzyme necessary for oxidative decarboxylation of ketoacids
Other congenital metabolic disorders
Leigh disease (subacute necrotizing encephalo-pathy)
Symmetric nonenhancing low-attenuation lesions. Similar lesions may be seen in globus pallidus, thalamus, hypothalamus, midbrain, periventricular white matter, centrum semiovale and cortical white matter. Brain atrophy may be seen
AR. Feeding difficulties and psychomotor retardation during first 2 years. Death occurs within 4 years
Wilson's disease (hepato-lenticular degeneration)
CT usually negative. Low-density lesions representing gliosis may be seen in basal ganglia, cerebral white matter, brainstem, and cerebellum
AR. Increased absorption of copper from intestine100
Hallervorden-Spatz disease
CT usually negative. Focal variation in density of globus pallidus, thalami, red nuclei, and substantia nigra
Rare AR with onset during second decade. Characteristic finding is abnormal iron accumulation in basal ganglia with variable degrees of neuronal loss
Infections and inflammations
Congenital herpes simplex encephalitis (type 2)
Early CT: Normal. Then bilateral symmetric low attenuation foci due to white matter edema, gray matter highly attenuating. Brain atrophy and gyri-form calcifications are late findings
Incidence: 1 in 2,000–5,000 live births. Brain involvement in 30%. Basal ganglia, thalami, and posterior-fossa relatively spared. May also cause visceral disease
Herpes encephalitis (type 1)
CT normal until 4 days. Later areas of hypodensity without enhancement, usually in bilateral temporal lobes, 20–50% bilateral. Hemorrhages in 50%. Late gyral enhancement may be seen
Fulminant, necrotizing meningoencephalitis, 70% cases adults, mortality of 70%
Acquired toxoplasmo-sis
Multiple bilateral low-density lesions with ring enhancement
Often progressive and fatal in immunosuppressed
SSPE
Only early finding edema, intermediate stage shows multifocal low-density areas in periventricular and subcortical white matter and parts of basal ganglia followed by generalized atrophy in advanced cases
Probably caused by reactivated measles virus in children and adolescents. Affects both gray and white matter. Cause progressive dementia and disorders of movement101
ADEM
CT may be normal. Bilateral confluent low attenuation changes in subcortical white matter.
Probably autoimmune reaction to previous infection/vaccination. Mortality 10–25%. Recovery complete
Brain abscesses
  • Early cerebritis stage (0–3 days): Low-attenuation mass effect with or without patchy or gyriform enhancement.
  • Late cerebritis stage (4–9 days): Low-density ring enhancing lesion with mass effect and edema.
  • Early capsule stage (10–13 days): Low- density ring enhancing lesion, smooth well-defined lesion.
  • Late capsule stage (days 14 and later): Abscess wall thickens and edema decreases with time
Usually focal, can be multifocal. Usually expands directly from temporal bone/frontal sinuses or arrives through trauma. Can be hematogenous. Differential diagnosis: Epidural abscess, subdural empyema, glioma, metastasis, chronic intracerebral hematoma, postoperative granulation tissue, multiple sclerosis, Lyme disease
Meningitis
CT normal in early cases; basal cisterns and sulci poorly visualized. Focal cerebral edema may be seen as low-density lesion. Parenchymal and leptomeningeal enhancement seen; complications like ventriculitis, communicating hydrocephalus, subdural effusion, cortical vein thrombosis, and later atrophy and encephalomalacia
Most often hematogenous. Follows course from meningeal congestion, through possible thrombosis, cortical infarction, cerebritis, or nidus abscess to exudate in basal cistern and sulci with thickened meninges102
AIDS
  • Low-attenuation lesion in white matter: HIV encephalitis as symmetric nonenhancing diffuse decrease of white matter attenuation. Progressive multifocal leukoencephalopathy less common, usually asymmetric decrease of attenuation in parieto-occipital areas.
  • Diffuse cerebral atrophy CNS lymphoma: 6–7% patients as enhancing periventricular/basal ganglia solid/ring lesion. Necrosis++
  • Infection: Multiple solid/ring enhancing lesion with edema around in basal ganglia characteristic of toxoplasmosis. Cryptococcosis characterized by small bilateral lesions possibly meningitis. CMV primarily seen in ependymal and sub-ependymal areas and cause ventriculitis
CNS involvement cause of initial complaint in 10%. Neurological s/s in one-third; most are opportunistic infections. HIV encephalitis causes white matter demyelination. PML caused by JC papovavirus is late finding with death within 3 months103
Cysticercosis
Can involve parenchyma, ventricles, and meninges cosis. Acute stage: Multifocal edema. Lesions may homogeneously enhance. Chronic stage: Single or multiple 4–20 mm fluid-filled cysts without enhancement. Cysts contain a mural soft tissue nodule; they later calcify in 70% and develops hydrocephalus in 70%
Caused by larval stage of pork tapeworm, Taenia solium. Presents as seizures and increased cranial pressure
TB
  • TB leptomeningitis: On unenhanced scans, para- sellar, perimesencephalic, and Sylvian cisterns obliterated by abnormal isodense soft tissue. Basal infarctions and communicating hydrocephalus. Granulomas may appear as solid/ring enhancing lesions
  • Tuberculoma: Hypodense parenchymal lesion with irregular contour. Nodular/ring enhancement
  • Diffuse leptomeningitis most common presentation of intracranial TB. CSF monocytosis, low sugar content, and high protein content
  • Tuberculomas may be indistinguishable from gliomas
Lyme disease (borreliosis)
Bilateral focal low-attenuation enhancing lesions due to demyelination and periventricular inflammation in deep cerebral white matter commonly frontal lobes
Tick borne multisystem disease caused by spirochete Borrelia burgdorferi. CNS affected in 10–15%: neuritis, meningitis, encephalitis, myelitis104
Neoplastic disease
Metastases
Commonly hypodense and enhance with contrast. Most necrotic mets are thick-walled and surrounded by vasogenic edema
15–30% intracranial tumors on CT are mets; initial clinical pre-sentation in 30% of lung cancers. Mets of melanoma, choriocar-cinoma, lymphoma, and osteosarcoma are hyperdense
Degenerative/vascular diseases
Normal aging brain
Mild-to-moderate enlargement of CSF spaces. Periventricular hypodensities
Atrophy progresses faster after 70 years of age, changes subtle on CT, obvious on MRI
Alzheimer's disease
Cerebral atrophy in anterior temporal lobes and hippocampus. Loss of distinction between gray and white matter. Decreased density in medial temporal lobes
Most common disorder causing dementia. Pathology: Neurofibrillary degeneration, senile plaques, nonspecific neuronal loss with reactive gliosis
Binswanger's encephalo-pathy
High ventricular and supraventricular nonenhancing white matter lucencies. Volume loss, lacunar infarcts in basal ganglia. Mild ventricular dilatation and sulcal widening, changes which overlap with normal aging and Alzheimer's disease
10% of dementia. Wide spectrum of changes including infarcts, myelin pallor, demyelination, hyaline arteriolar sclerosis, and gliosis105
Multiple sclerosis
CT usually negative. Isodense/hypodense white matter foci, which in active demyelination phase may show contrast enhancement. Can mimic neoplasm by having mass appearance with ring enhancement
Most common demyelinating disease. Most common in periventricular white matter, more common in females. CT insensitive in detecting lesions
Schilder's disease
Confluent hypodensities represent areas of demyelination which may show contrast enhancement
May be virulent childhood form of multiple sclerosis. d/d: Childhood adrenoleukodystrophy
Marchiafava-Bignami disease
Well-defined lucency in genu of corpus callosum
Rare selective myelinolysis in corpus callosum, less often in deep white matter. Occurs mainly in alcoholic, malnourished persons
Central
Pontine myelinolysis
CT normal, nonenhancing low-density lesions in pons without mass effect may occur. Other areas (basal ganglia and thalami) may be involved
In alcoholic malnourished persons and in those treated with electrolyte and acid-base abnormalities. d/d: Multiple sclerosis, infarct, encephalitis, neoplasm. Thought to be associated with rapid rise in serum sodium concentration: greater than 20 mEq/L in 1–3 days
(ADEM: acute disseminated encephalitis; SSPE: subacute sclerosing panencephalitis)