INTRODUCTION
Knowing historical facts relating to a specific area, provides the reader with a better understanding and appreciation for the efforts undertaken by previous pioneers. In this introductory chapter, we wish to provide the reader with a glimpse to the past of Neuroendoscopy and how the discipline evolved. Key technical advances made by a few and courageous clinicians/surgeons and their disciples have led to our current state of affairs where we can provide our patients with minimally invasive, safe and successful surgical options.
ENDOSCOPIC PREHISTORY
Endoscopy has existed, albeit in a crude form, since the time of the ancient Egyptians around 1550 BC.1 Their practice of transnasal excerebration involved the use of hook-shaped rods that helped them peer inside the human nasal cavity and extract cerebral components during mummification. This technique has been postulated by some to be the earliest example of minimally invasive neurosurgery.2 The approach used by the ancient Egyptians (as depicted by Herodotus in his book Histories) is surprisingly similar to modern-day transphenoidal surgery.1
The next phase of endoscopic evolution deals with the development of speculum technology. The Talmud, which dates back to 1300 BC, contains a description of a speculum precursor that was used to examine Jewish women in order to determine their eligibility to participate in sexual intercourse.2 Specula were also used by physicians like Hippocrates between 460 BC and 370 BC.3 Excavations conducted in Dion, a village located in northern Greece, uncovered bronze instruments that bear a resemblance to the specula used by modern physicians. The instruments from Dion date back to approximately 200 BC; tools of similar construction from around 70 AD have also been recovered from the ruins of Pompei (Fig. 1).
Speculum implementation was advanced by Albukasim of Cordoba (936–1013 AD), an Arabian physician who used reflected ambient light during his examinations to aid visibility.3 In 1585, Giulio Cesare Aranzi improved on this technique by using closed tubes and mirrors to reflect ambient light into the nasal cavity.3 This eventually paved the way for the “Godfather” of modern endoscopy, Philipp Bozzini (1773–1809), whose “Lichtleiter” or “light guide” used a candle as an external light source along with a set of reflective mirrors on one end of the device and various examining tubes that could be fitted to the opposite end.2
Fig. 1: Ancient Greek specula recovered from the ruins of Pompei, dated around 70 AD.Source: Reprinted with permission from Elsevier. Abd-El-Barr MM, Cohen AR. The origin and evolution of neuroendoscopy. Childs Nerv Syst. 2013;29:727-37.
Fig. 2: One of the first endoscopic tools: Philipp Bozzini's “Lichtleiter” or light guide, 1805.Source: Reprinted with permission from Elsevier. Edmonson JM. History of the instruments for gastrointestinal endoscopy. Gastrointest Endosc. 1991;37:S27-56.
Fig. 3: Illustration depicting Antonin Desormeaux's endoscope. The kerosene lamp at bottom of device burned alcohol and turpentine to fuel illumination.
THE FIRST ENDOSCOPES
Bozzini was hopeful that his endoscopic device (Fig. 2) could be used to visualize body cavities, but he encountered some resistance in the process of trying to legitimize his invention. Although many ecclesiastical prohibitions banning the exploration of human anatomy had been lifted since the Renaissance, the church's influence was still not totally withdrawn from the activities of the scientific community. Church officials halted the progress of Bozzini's invention during its second round of testing when they withheld their approval for the Lichtleiter to be used on live patients.2 Because of petty rivalries already in place, the device was ridiculed by the Alert Faculty of the University of Vienna and subsequently rejected.2 Bozzini's work was not appreciated in its time, but his three part design principle of a light source, reflective mirrors, and an investigative eye piece remains a staple guide for the construction of endoscopic technology even within our modern age.
Despite the widespread opposition against Bozzini's invention, there were two individuals who followed his model and tried to improve his work: Pierre Salomon Segalas and John D Fisher. Their endoscopic instruments resembled the Lichtleiter through the incorporation of a light source, a reflective surface, and a graduated series of tubular specula.4 Fisher added a double convex lens to sharpen and enlarge the image produced by his endoscope while Segalas modified his scope to visualize bladder stones and then crush them with a lithotrite.4 Segalas is also noteworthy because his guidance informed the work of the individual responsible for the next major innovative leap in endoscopic design: French urologist Antonin Desormeaux.4
Desormeaux is credited with several “firsts” in endoscopic history. In 1853, he designed a scope with a kerosene lamp that burned alcohol and turpentine (Figs. 3 and 4) coupled with a 45° mirror that could reflect that lamp's light into different parts of the body.3,5 Some scholars consider this cystoscope (an endoscope used specifically for visualizing the urinary bladder through the urethra) to be the first proper endoscope.6 Desormeaux used this instrument to remove a papilloma from a patient's urethra, which was recognized as the first recorded therapeutic use of an endoscope.6 He is also credited as being the first person to use the term “l'endoscopie” (endoscopy).3
The problem with Desormeaux's device was that while it produced better illumination, the heat emitted from the lamp's galvanized platinum wires was so intense that it could easily burn a patient. German dental surgeon Julius Bruck was able to alleviate this problem, in part, when he designed a glass cooling system that diminished heat emission with a stream of water surrounding the platinum filament.33
Fig. 5: A prototype of the Nitze-Leiter cystoscope, 1877.Source: Reprinted with permission from Elsevier. Herr HW. Max Nitze, the cystoscope and urology. J Urol. 2006;176:1313-6.
It is unclear whether or not Bruck was able to implement his design in a clinical setting, but his cooling system as well as the placement of his light source were both significant contributions to the field.2 The notion to place a light source inside the human body was particularly important because all sources of light used for endoscopic visualization up to that point in time had been external.
NITZE AND THE MODERN ENDOSCOPE
German physician Maximilian Nitze also recognized the limitations created by external light sources. He wanted to incorporate Bruck's ingenious lighting system into a prospective design, but felt that the endoscope's small field of view still posed a problem for the operator. He supposedly got the inspiration for a solution to this problem while cleaning the eyepiece of his microscope. When he looked out through the lens, Nitze realized that he could see through it clear across to a neighboring church; this observation led him to incorporate a telescoping system into his design in order to obtain a wider field of view.2 Nitze's concept was a major step in endoscope evolution because it finally afforded the device magnification, a quality all previous systems lacked up to that point because they were simply tubes that directed light down to their distal tips.7
In 1879, Nitze collaborated with Austrian engineer Josef Leiter to produce a cystoscope that used Bruck's water-cooled platinum filament lamp at its distal end along with a series of telescoping optical lenses set inside a metal tube that would relay an image down the scope.2,3 Although it was the first endoscope to combine all these crucial elements (Fig. 5), the device was still burdened by insufficient illumination, cumbersome usage, and expensive operation costs.6 Eight years after Thomas Edison's incandescent light bulb became commercially available, Nitze incorporated it into the distal end of his cystoscope, which made the instrument much more manageable and gained the physician widespread acclaim in the process.2
NEUROENDOSCOPY EMERGES
Before the 19th century, there were several obstacles in place that hindered the successful application of endoscopy to the field of neurosurgery. For example, compared to the gastrointestinal tract the brain is a much darker organ; it cannot be illuminated sufficiently by ambient sources of light.8 Another difficulty was that early anatomists had a flawed understanding of neurophysiology that perpetuated misconceptions about cerebrospinal fluid (CSF) and the structure of the brain's cavities.8 But 4by the 20th century, substantial work had been done that mapped out the ventricular and subarachnoid spaces and, thanks to Nitze's contributions, physicians were finally equipped with the tools they needed to explore those dark corridors.
Endoscopes were finally used for neurosurgical purposes in 1910, when American urologist Victor L’Espinasse introduced a cystoscope into the lateral ventricle and bilaterally fulgurated the choroid plexus of two infants suffering from hydrocephalus.9 One patient died postoperatively and the second lived for 5 years before passing.10 L’Espinasse himself did not seem to think much of the endeavor. He presented his work at a local meeting, but never formally published it.2 He later wrote the operation off as a sort of novelty, describing the procedure to his daughter, Victoire (also a physician), as “an intern's stunt”.10 Still, in spite of this modest assessment, the long-term impact made by his experimental foray into neurosurgery should not be understated. Readers should not gloss over the fact that the first person to perform neuroendoscopic surgery was not a neurosurgeon, but a young urologist with an unprecedented idea. His example can serve us as a reminder about the importance of innovation and inter-discipline dialogue.
THE DANDY YEARS
Although L’Espinasse deserves credit for being the first person to perform neuroendoscopic surgery, the acknowledged father of modern neuroendoscopy is Walter E Dandy, who used the endoscope in his study and treatment of hydrocephalus. Dandy determined that communicating hydrocephalus could be alleviated by extirpating the choroid plexus. Doing so would reduce the production of CSF, which was out of balance due to an obstruction in the subarachnoid space.11 In 1918, he published a manuscript describing this extirpation.11 It was a somewhat crude procedure that required a nasal dilator to keep the cortex open and necessitated that he drain the patient's entire volume of CSF before removing the choroid plexus.2 The operation left three out of four patients dead within 1 month of treatment; the fourth survived and showed no signs of hydrocephalus 10 months after surgery.2
In 1922, Dandy tried to incorporate a cystoscope into these choroid plexectomies.12 Unfortunately, he was unable to complete the operations without assistance from his nasal dilator and forceps.8 Though these initial attempts were not successful, Dandy was steadfast in his efforts. During the same year, he published the first endoscopic observations of the ventricles and coined the term “ventriculoscopy”.9 Dandy was enthusiastic about refining his approach, but admitted that the images created by his ventriculoscope did not surpass in quality those produced by the more routine pneumoventricolography technique.9 He reluctantly concluded that neuroendoscopy had little to offer brain surgery that could not be achieved through conventional means.8
Elsewhere, while Dandy struggled to find a space for neuroendoscopy, progress was being made by his contemporaries. In 1923, William Mixter published the first report describing an endoscopic third ventriculostomy in a patient with noncommunicating hydrocephalus.13 During the same year, Fay and Grant reported the first black and white photos taken of a child's dilated ventricles, which they took using a cystoscope affixed with a camera.9,13 In 1936, John Scarff performed an endoscopic plexectomy using a new version of the ventriculoscope made of a tube with an inner stylet connected to irrigation channels that maintained constant intraventricular pressure; this prevented the ventricular collapse that might have contributed to Dandy's poor initial results.9
In spite of his skepticism, Dandy did not completely abandon the prospect of endoscopy playing a larger role in neurosurgery. He turned to Howard Kelly (the renowned father of cystoscopy) for design advice and personally directed engineers from the Wappler Electric Co. in order to construct a better ventriculoscope.8 He also took notice of the advancements made by his peers. In 1934, Tracey J Putnam adapted a urethroscope for endoscopic electrocautery and introduced endoscopic choroid plexus coagulation, a procedure that could successfully obliterate the choroid plexus without the need for resection.8 The operation was different from Dandy's because the CSF was not completely evacuated from both ventricles before cauterization of the choroid plexus took place.14 Dandy eventually adopted this coagulation technique when performing his own endoscopic choroid plexectomies; he also used a probe similar to Putnam's that could be threaded through the scope.8
By 1945, despite the progress he had made, Dandy ultimately considered the endoscope's neurosurgical application to be restricted to young children with ventricular tumors or older patients with tumors that had accidentally disclosed during choroid plexectomies.8 5Because he was a prominent surgeon who played such a huge role in pioneering the technique, Dandy's criticism of neuroendoscopy might have contributed to the 20-year period of stagnation that followed.8 The lack of endorsement was not the only factor, of course. Ventricular CSF shunt surgery and microsurgery both minimized the need for neuroendoscopy to be further explored in the coming generation.
THE DECLINE AND REBIRTH OF NEUROENDOSCOPY
In 1951, Nulsen and Spitz described a treatment for hydrocephalus using ventricular shunt placement.6 Because it was easier to perform and had lower associated mortality rates than other available techniques, shunting quickly became popular.12 In the 1960s, the emergence of microneurosurgery also played a role in neuroendoscopy's decline because the microscope provided surgeons with everything the endoscope seemed to lack: high magnification, adequate illumination, and the ability to work in deep structures with little damage to the surrounding tissue.2 While interest in neuroendoscopy waned during this era, there were several technological advancements taking place that helped set the stage for the field's resurgence in the 1970s. These included the development of fiber optics, the rod-lens system, SELFOC (self-focusing) lenses, and charged-coupling devices (CCDs). Many of these advancements can actually be connected to a single individual: British optical physicist Harold Hopkins. It is primarily because of his contributions that the endoscope became a viable surgical tool after so many years of dormancy.
FIBER OPTICS
In 1951, Hopkins was at a dinner party seated next to a gastroenterologist who complained about the shortcomings of endoscopic technology.2 Most scopes available at the time followed Nitze's design, which used a series of lenses housed in an air-filled tube. This system engendered several problems for the operator, including color distortion, poor illumination, excessive heat, cumbersome size, and rigidity.7 While working with research student Narinder Kapany, Hopkins utilized coherent bundles of glass fibers to create the fiberscope, a flexible device with a shaft that could be bent and still conduct an image from one end to the other.3,7 The glass fibers also permitted the transmission of light without excessive heat.12
Although Hopkins was the person who successfully manifested them into a practical tool, some of the concepts that made up his fiber optic technology had already been described by previous researchers. For example, Heinrich Lamm demonstrated that light could be conducted through a bundle of glass fibers in 1932.7 Daniel Colladon and Jacques Babinet demonstrated the earliest light conductors in the 1840s.13
ROD-LENS SYSTEM
Although the advancements produced by Hopkins’ fiberscope were helpful, the device was still lacking, particularly when it came to image quality and light transmittance. In 1959, Hopkins was approached by James G Gow, a urologist who wanted to take photographs of the inside of the bladder in order to develop cancer therapies.3 He needed the current cystoscope improved so that it could provide superior illumination. This prompted Hopkins to develop the rod-lens system, which replaced the large gaps of air in between a series of small lenses that were found in Nitze's endoscope with large glass rods in between a series of small air spaces.3 This new design allowed those spaces of air to act as a series of thin lenses, which resulted in an all-around superior experience for the user.
The conduction of light in an endoscope is a function of the refractory index of the conducting medium.7 In the case of Nitze's telescoping design, that medium was air. Hopkins realized that glass has a refractory index that is 1.5 times greater than air. By exchanging glass for air and air for glass, the system's refractory index increased, which significantly expanded the scope's field of vision and light gathering capacity.7 This adjustment also reduced the diameter of the endoscope, which made it less invasive for patients.3 The rod-lens system was a crucial innovation in design that made the endoscope so much more effective. It still forms the basis of the rigid endoscopes that are currently used today.2
SELFOC LENS
In 1966, Hopkins collaborated with German optical instrument manufacturer Karl Storz to design a rigid endoscope that used a new type of lens: the self-focusing optical (SELFOC) lens.3 While conventional lenses have a uniform refractive index, the SELFOC lenses contain a gradient index glass with a variable refractive index that changes according to the radial dimension of the lens.12 6Conventional endoscopes used during this time period required the meticulous placement of relay and field lenses to construct an image. The SELFOC lens technology essentially eliminated the need for relay lenses while creating a wider field of vision and preserving light conduction.12 Surgeons were able to operate without making large incisions and could peer into body cavities with more clarity than ever before. This refined endoscope was made commercially available in 1967 and marked the technological beginning of modern neuroendoscopy as we know it today.3
CHARGED-COUPLING DEVICES
Charged-coupling devices are solid-state devices that are capable of converting optical data and light signals into electrical impulses and digital data.3,12 They were invented by Willard Boyle and George Smith in 1969 in order to address the question of how to incorporate video camera technology into endoscopic operations.3 CCDs decreased the size of endoscopic systems and improved the quality of their transmitted images by conducting them over to high-resolution screens.3
NEUROENDOSCOPY: YESTERDAY, TODAY, AND TOMORROW
In the 1970s, after decades of disinterest, neurosurgeons started to reconsider endoscopy's role as a surgical tool. This resurgence can be attributed to several factors. Other specialties had already demonstrated the benefits of minimally invasive surgery (shorter convalescence period, lower morbidity rates, and greater patient satisfaction).15 Endoscopic tools had become smaller and more efficient. They were easier to use and provided superior imaging than their predecessors. Perhaps the main reason why neurosurgeons revisited endoscopy was because of the complications related to CSF shunting, such as shunt malfunction, infection, migraines, and overdrainage.12 Shunt failure was (and still is) an especially dangerous risk for patients in developing countries because those individuals might live far away from facilities that could repair a faulty shunt.2 Endoscopic third ventriculostomy is often preferable to shunt surgery because it offers a more physiological solution to the problem posed by hydrocephalus: it allows the ventricular CSF to drain directly into the subarachnoid space.12
In 1973, Takanori Fukushima introduced the first flexible neuroendoscope (the “ventriculofibroscope”), which was used to explore treatments related to intraventricular tumor biopsy, cyst fenestration, and hydrocephalus.9,15 However, it was not until 1994 that Jones and colleagues described an endoscopic third ventriculostomy procedure that had a 61% success rate in treating hydrocephalus.12 Since that time, endoscopic third ventriculostomy and choroid plexus cauterization have both become popular treatment options for hydrocephalus. Their success recovered neuroendoscopy's once-damaged reputation and suggested to curious neurosurgeons the possibility that this approach could be applied to other areas of surgical interest as well.
Neuroendoscopy is currently being used to treat many other kinds of disorders, including skull base tumors, intraventricular tumors, intracranial cysts, degenerative spine disease, and craniosynostosis.12 However, some of these applications offer unique obstacles that must be addressed before the field can progress any further. Some of the challenges associated with intraventricular surgery include operating within a fluid medium, achieving hemostasis, performing bimanual microdissection, and maintaining optimized visualization.13 The development of direct endoscopic visualization (endoscope-controlled microsurgery) will likely facilitate bimanual microdissection and assist in the maintenance of hemostasis for intraventricular lesions.13 Improvements made to endoscopic instrument design, such as the development of a miniaturized endoscopic ultrasonic aspirator, should also enable surgeons to resect lesions with more accuracy and safety.13
Skull base endoscopy is a much younger field than intraventricular endoscopy. While intraventricular investigation rebooted in the 1970s and 1980s, a routine endoscopic approach to skull base pathology was not firmly established until almost 20 years later.13 Challenges endemic to endoscopic skull base surgery have included demarcating surgical boundaries that are limited by critical neurovascular structures, maintaining hemostasis, losing binocular vision, and developing sufficient skull base reconstruction techniques.13 Much work has been done to address these limitations so that safe access along a wide arc of the midline skull base from the frontal sinuses to the odontoid process is now attainable.13
One of the main reasons why endoscopy is so appealing is because it is minimally invasive. This attribute has been particularly beneficial to peripheral nerve applications, such as carpal tunnel decompressions.13 Carpal tunnel decompression took off in the late 1980s and is 7now the operation of choice for many surgeons because of its excellent success rates and low complication rates.13 Endoscopic approaches have been considered for other peripheral nerve surgeries as well, including ulnar nerve decompressions.13
In the future, flexible endoscopes and wireless camera technology could reduce our dependence on the rigid rod-lens system.13 Robotic endoscopic devices might provide more sophisticated panoramic and circumferential views of the ventricular system and three-dimensional endoscopic technology could potentially compensate for the loss of binocular vision currently associated with contemporary endoscopic technology.13 Robot-assisted systems might equip surgeons with the ability to perform techniques that could not otherwise be executed in confined spaces like the ventricular system or the paranasal sinus, but one major limitation of such surgery would be the loss of haptic feedback that normally exists during standard procedures.13 That problem could potentially be overcome, but only with sufficient advancement in haptic sensor and pressure generator technology.
Endoscopic investigation began centuries ago, with vague conceptions and primitive instruments. The field persisted thanks to the tenacity and ingenuity of innovators from various specialties, but its progress was still slow. A practical, reliable endoscope did not emerge until only recently, within the last 60 years. The incorporation of endoscopic technique into routine neurosurgery took time to establish because the first operations that used it were fraught with so much danger and technical difficulty.
After its associated technology improved, neuroendoscopy finally started to build up its reputation. It is no longer merely a feasible technique; in many cases it is the preferred treatment option. Some consider its comprehension to be an absolute necessity for neurosurgeons and suggest that it will soon become the standard of care by which many of today's procedures are performed.16 Although neuroendoscopy has flourished since the time of its humble origins, with the right technological advancements bolstering it there is still much room left for it to grow, both in terms of general efficacy and surgical application.
REFERENCES
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- Abd-El-Barr MM, Cohen AR. The origin and evolution of neuroendoscopy. Child's Nerv Syst. 2013;29(5):727–37.
- Di Ieva A, Tam M, Tschabitscher M, et al. A Journey into the technical evolution of neuroendoscopy. World Neurosurg. 2014;82(6):e777–89.
- Edmonson JM. History of the instruments for gastrointestinal endoscopy. Gastrointest Endosc. 1991;37(2 Suppl): S27–56.
- Lau WY, Leow CK, Li AK. History of endoscopic and laparoscopic surgery. World J Surg. 1997;21(4):444–53.
- Schmitt PJ, Jane JA, Jr. A lesson in history: the evolution of endoscopic third ventriculostomy. Neurosurg Focus. 2012;33(2):E11.
- Abbott R. History of neuroendoscopy. Neurosurg Clin North Am. 2004;15(1):1–7.
- Hsu W, Li KW, Bookland M, et al. Keyhole to the brain: Walter Dandy and neuroendoscopy. J Neurosurg Pediat. 2009;3(5):439–42.
- Decq P, Schroeder HW, Fritsch M, et al. A history of ventricular neuroendoscopy. World Neurosurg. 2013;79(2 Suppl):S14.e1-6.
- Grant JA. Victor Darwin Lespinasse: a biographical sketch. Neurosurgery. 1996;39(6):1232–3.
- Dandy WE. Extirpation of the choroid plexus of the lateral ventricles in communicating hydrocephalus. Ann Surg. 1918;68(6):569–79.
- Li KW, Nelson C, Suk I, et al. Neuroendoscopy: past, present, and future. Neurosurg Focus. 2005;19(6):E1.
- Zada G, Liu C, Apuzzo ML. Through the looking glass: optical physics, issues, and the evolution of neuroendoscopy. World Neurosurg. 2013;79(2 Suppl):S3–13.
- Azab WA, Shohoud SA, Alsheikh TM, et al. John Edwin Scarff (1898-1978) and endoscopic choroid plexus coagulation: a historical vignette. Surg Neurol Int. 2014;5:90.
- Shiau JSC, King WA. Neuroendoscopes and instruments. In: Jimenez DF (Ed). Intracranial Endoscopic Neurosurgery. Neurosurgical Topics. Park Ridge, IL: The American Association of Neurological Surgeons; 1998. pp. 13–27.
- Nobles AA. The physics of neuroendoscopic systems and the instrumentation. In: Jimenez DF (Ed). Intracranial Endoscopic Neurosurgery. Neurosurgical Topics. Park Ridge, IL: The American Association of Neurological Surgeons; 1998. pp. 1–12.