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Abstract Equine herpesvirus type 1 and 4 (EHV-1 and EHV-4) glycoprotein H (gH) has been hypothesized to play a role in direct fusion of the virus envelope with cellular membranes. To investigate gH’s role in infection, an EHV-1 mutant lacking gH was created and the gH genes were exchanged between EHV-1 and EHV-4 to determine if gH affects cellular entry and/or host range. In addition, a serine-aspartic acid-isoleucine (SDI) integrin-binding motif present in EHV-1 gH was mutated as it was presumed important in cell entry mediated by binding to α4β1 or α4β7 integrins. We here document that gH is essential for EHV-1 replication, plays a role in cell-to-cell spread and significantly affects plaque size and growth kinetics. Moreover, we could show that α4β1 and α4β7 integrins are not essential for viral entry of EHV-1 and EHV-4, and that viral entry is not affected in equine cells when the integrins are inaccessible.

Background: Isolated sphenoid sinus fungal mucoceles are extremely rare and potentially associated with visual disturbances, cranial nerve (CN) deficits, or pituitary dysfunction. Their initial symptoms are often absent or nonspecific, and routine examination offers little information, resulting in diagnostic and therapeutic delays. A high index of suspicion and a thorough understanding of their clinical presentation, neuroradiological features, microbiological implications, and complication profile are crucial for early diagnosis and prompt management. We, herein, analyze a series of consecutive cases of isolated sphenoid sinus fungal mucoceles whom we treated, add to the currently existing published cases, and review the pertinent literature., Methods: From the databases of endoscopic endonasal skull base and rhinological surgical procedures maintained by our groups, all cases with isolated sphenoid sinus fungal mucoceles were retrieved and included in the study. Clinical and radiological findings, histopathologic evidence of fungal rhinosinusitis, culture results, clinicopathological designation, treatment details, and outcome of CN neuropathies were analyzed., Results: Headache was the most common symptom (seven cases). Oculomotor (three cases) and abducens (two cases) nerve palsies were encountered in five out of eight patients. Visual loss was seen in two cases. Hypopituitarism was seen in one case. All patients underwent endoscopic endonasal wide bilateral sphenoidectomy. CN palsies improved in four out of five cases., Conclusion: Endoscopic endonasal wide sphenoidectomy is the surgical treatment of choice and should be performed in a timely manner to prevent permanent sequelae. Histopathological and microbiological examination findings should both be obtained as they dictate the next steps of therapeutic intervention., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Surgical Neurology International.)

Pseudotumoral encephalic schistosomiasis (PES) is the chronic form of cerebral neuroschistosomiasis, and is rarely encountered in clinical practice. Clinically, PES closely resembles other intracranial space-occupying lesions including brain tumors. Laboratory investigations are usually inconclusive, and neuroradiologic findings are frequently reported as non-specific. Such diagnostic difficulties may result in delayed diagnosis and treatment. Across the literature, there is a paucity of information about and controversy over many aspects of the disease. Particularly, inconsistent magnetic resonance imaging (MRI) findings, a wide variation of medical treatment protocols, lacking consensus regarding the indications of surgery, and undetermined information regarding the impact of the extent of resection on prognosis. We herein review the pertinent literature with the aim of providing focused information regarding the pathogenesis of PES, its currently identified more distinctive neuroimaging features, and the indications and extent of surgery in light of the state-of-the-art operative neurosurgical practice. A distinctive multinodular arborizing pattern of PES lesions can often be observed on MRI in patients with PES. Praziquantel is considered by many authors to be the drug of choice in all cases, and seems to be effective at variable dose regimens. Although lesion excision utilizing current technology is generally safe, the indications and extent of surgery are still undetermined and should be decided on a case-by-case basis. Multicenter collaborative research is further needed to fill the existing gaps in the current knowledge on PES., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Fully endoscopic or endoscope-controlled approaches are essentially keyhole approaches in which rigid endoscopes are the sole visualization tools used during the whole procedure. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Fully endoscopic retrosigmoid approach for cerebellopontine angle tumors is a minimally invasive approach that is not routinely practiced by neurosurgeons, with few series published so far. Unfamiliarity with the technique, steep learning curve, and concerns about inadequate exposure, neurovascular injury, and decreased visibility may explain this fact. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic retrosigmoid approach and present an overview of the published series., Methods: From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic retrosigmoid approach for cerebellopontine angle tumors were retrieved and analyzed. The pertinent literature was also reviewed., Results: The surgical technique of the fully endoscopic retrosigmoid approach was formulated., Conclusion: The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Background: Anterior cranial base meningiomas include those meningiomas originating from the tuberculum sellae, the planum sphenoidale, or the olfactory groove, with surgical excision being the main treatment modality for these tumors. Conventional microscopic and endoscope-assisted versions of the supraorbital keyhole approach via an eyebrow incision emerged into minimally invasive options that are frequently utilized nowadays for treating these tumors. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Notwithstanding, the fully endoscopic or endoscope-controlled version of the supraorbital keyhole approach is not routinely practiced by neurosurgeons, with few series published so far. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic supraorbital approach for anterior cranial base meningiomas., Methods: From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic excision of anterior cranial base meningiomas via supraorbital approach were retrieved and analyzed. The pertinent literature was also reviewed., Results: The surgical technique of the fully endoscopic supraorbital approach for anterior cranial base meningiomas was formulated., Conclusion: The fully endoscopic supraorbital approach for anterior cranial base meningiomas has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Background: Osteomas are the most common primary bone tumors of the calvaria, with an incidence of less than 0.5%. In skull vault osteomas, the exostotic form that grows from the outer table is more common than the enostotic ones which arise from the inner table and grow intracranially. Osteomas of the forehead are very noticeable and disfiguring; patients usually seek medical advice for cosmetic reasons. Forehead osteomas were traditionally excised via either a direct incision over the lesion using the naturally occurring creases or a conventional bicoronal flap. More recently, endoscopic approaches for excision of forehead osteomas were introduced. The results were very encouraging and the technique was adopted by many groups worldwide yet with many technical variations. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic resection of frontal osteomas., Methods: From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases of forehead osteomas were retrieved and analyzed. The pertinent literature was also reviewed., Results: The surgical technique of the fully endoscopic resection of frontal osteomas was formulated., Conclusion: The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be less time-consuming, efficient, and minimally invasive with excellent cosmetic results., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Background: Fully endoscopic or endoscope-controlled approaches are essentially keyhole approaches in which rigid endoscopes are the sole visualization tools used during the whole procedure. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Fully endoscopic resection of intraparenchymal brain tumors is a minimally invasive approach that is not routinely practiced by neurosurgeons, with a few major series published so far. Unfamiliarity with the technique, steep learning curve, and concerns about inadequate exposure and decreased visibility may explain this fact. The majority of the purely endoscopic resections for intraparenchymal brain lesions are performed nowadays through tubular retractor systems. In very limited instances, however, the fully endoscopic technique is performed without tubular retractors. In this chapter, we elaborate on the surgical technique and nuances of the fully endoscopic nontubular retractor approach for intraaxial tumors., Methods: From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, and operative charts and videos of cases undergoing fully endoscopic excision for intraaxial brain tumors were retrieved and analyzed. The pertinent literature was also reviewed., Results: The surgical technique of the fully endoscopic nontubular retractor approach for intraaxial tumors was formulated., Conclusion: The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

This chapter is intended to provide a brief overview of the optics of surgical microscopes and rigid endoscopes, with the aim of providing the reader with the principles dictating the nature of surgical visualization when either of the visual control systems is used. It is not by any means geared toward elaborating on the detailed optical physics of these systems, which is beyond the scope and objective of this chapter., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Background: One of the main difficulties in third ventricle surgery is its deep and central location within the brain, surrounded by many eloquent neurovascular structures. Such anatomical environment obviously makes it very hard to safely approach and excise lesions in there., Methods: The introduction of the surgical microscope into the neurosurgical field undoubtedly played an important and pivotal role in improving the surgical results and increasing the safety of operations in and around the third ventricle. Although the surgical microscope remained the gold standard of intraoperative visualization for many decades, the advent of endoscopes revolutionized surgery of the third ventricle. Neuroendoscopic procedures for lesions of the third ventricle encompass a greatly variable array of endochannel, endoscope-assisted and endoscope-controlled techniques., Conclusion: In this collection on purely endoscopic and endoscope-assisted approaches to lesions of the third ventricle in pediatric age, the readership is presented with a selected group of these operations performed by experts in the field, shedding light mainly on their technical aspects and surgical pearls. The text description in each article is supplemented by a surgical video., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Endoscopic skull base surgery has become an integral part of the present neurosurgical armamentarium. The pioneering efforts in which the purely endoscopic transsphenoidal approach was introduced have triggered a growing tide of using the endoscopic endonasal procedures for a large variety of skull base lesions. Because of their anatomical peculiarities, lesions of the sellar and parasellar regions lend themselves very well to the endoscopic endonasal approaches. Apart from the common pathological entities, many other less frequent pathologies are encountered in the sellar and parasellar area. In this chapter, we review the surgical technique of the endoscopic endonasal transsphenoidal approach and its extensions applied to a variety of rare and uncommon pathological entities involving the sella turcica and clivus. An overview of these pathological entities is also presented and exemplified., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Persisting embryonal infundibular recess (PEIR) is a very rare anomaly of the floor of the third ventricle in which the embryonic morphology of the infundibular recess (IR) persists. The exact underlying mechanism of development of PEIR is unknown, and the anomaly has been reported as an isolated finding or in association with other conditions. On the other hand, trans-sphenoidal encephaloceles are the rarest form of basal encephaloceles. The trans-sphenoidal trans-sellar encephalocele (TSE) is the least common variant in which the pituitary gland, pituitary stalk, optic pathways, parts of the third ventricle and IR may be present within the encephalocele. We recently treated one patient with TSE. Based on the observed morphological similarity of the IR in our patient and in the published cases of PEIR, we reviewed the literature in order to validate the hypothesis that PEIR and TSE may possibly belong to one spectrum of malformations. Across the published reports, the morphology of the IR in TSE is very closely similar to PEIR. Moreover, radiological, patho-anatomical, and embryological evidence is in support to our hypothesis that PEIR and TSE are most likely the two extremes of the same continuum of malformations., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Little is known on the impact of the pattern and extent of pneumatization of the sphenoid sinus (SS) on the dimensions of the surgical windows used in extended endoscopic endonasal transsphenoidal approaches. We therefore investigated whether the distances between the 2 optic canals and between the paired paraclival carotid arteries are influenced by the pattern and extent of pneumatization of the SS., Methods: One hundred high-resolution computed tomography scans from 47 adult female and 53 adult male patients were analyzed. The pattern of SS pneumatization was classified into conchal, presellar, and sellar types. Sellar-type sinuses were then classified according to a newer detailed classification system. Maximal anteroposterior (AP), transverse (TR), and craniocaudal diameters of the SS, interoptic distance at the limbus sphenoidale (IODL) and at the entrance of the optic canal (IODE) and the intercarotid distance between the paraclival carotids (ICD) were measured. A 2-tailed Mann-Whitney U test and Pearson correlation coefficient (R) were used for statistical analysis. A P value <0.05 was considered statistically significant., Results: Positive correlation was found between IODL and both AP and TR diameters of the SS; between IODE and both AP and TR diameters of the SS; and between ICD and all diameters of the SS. The highest correlation for each of the IODL, IODE, and ICD was noted with the TR diameter of the SS., Conclusions: During the development of the SS, pneumatization progress likely exerts quantitative and direction-specific forces, which gradually increase the interoptic and intercarotid distances., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Despite the superb visualization offered by the endoscopic endonasal transsphenoidal approach, the resection rates of large and giant pituitary adenomas have remained much lower than those of smaller macroadenomas. Various tumor characteristics can influence the extent of resection (EOR) and have been variably reported. Additional understanding of these factors is mandatory to improve the results. We analyzed the radiological and intraoperative tumor characteristics influencing the EOR in a cohort of patients with large and giant pituitary macroadenomas undergoing endoscopic endonasal transsphenoidal excision under our care., Methods: Twenty-eight patients were included. Magnetic resonance images were retrospectively analyzed for pre- and postoperative tumor volumetric analysis; preoperative tumor volume calculation using the formula (A × B × C/2); preoperative radioanatomical characteristics, including tumor shape, radiological structure, contrast enhancement, and extension; and the EOR. Intraoperative data were retrieved and included., Results: The preoperative calculated tumor volume was 38.14 ± 23.02 cm 3 and the preoperative measured tumor volume was 50.345 ± 17.36 cm 3 . A statistically significant difference was found between the calculated and measured tumor volumes for the whole cohort and for tumors with a maximum diameter >3.9 cm. A statistically significant difference in the EOR was found at a volume threshold of 26.2 cm 3 . Large cysts, heterogeneous enhancement, Knosp grade ≤2, soft tumor consistency, and tumor hemorrhage were significantly associated with gross total resection., Conclusions: Volumetric analysis should replace 2-dimensional methods in determining the size of large and giant pituitary adenomas. Specific tumor characteristics were associated with the EOR and could help in predicting the EOR for these tumors., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: The main criticism of endoscopic excision of colloid cysts of the third ventricle is the decreased ability to completely resect the cyst wall, therefore increasing the risk of recurrence. The extent of resection varies widely across the endoscopic series and is largely influenced by the surgical technique. We report the results of the rotational technique for endoscopic transforaminal excision of colloid cysts in a series of consecutive patients. Our objective is to contribute to the current literature and to shed more light on an effective and safe yet less commonly used technique., Methods: Retrospective analysis was performed on 19 patients. Preoperative magnetic resonance imaging (MRI) was evaluated for cyst characteristics. Postoperative MRI was evaluated for residual cyst membranes. Operative records were reviewed for residual cyst components. Excision grade was determined based on the Barrow Neurological Institute grading scale. Symptom resolution was documented clinically., Results: The study included 13 men and 6 women, with a mean age of 35 years (range, 19-56 years) and mean follow-up of 27.74 months (range, 4-55 months). Total excision was achieved in 17 of 19 cysts (89.5%). A small residual was seen intraoperatively but not radiographically in 1 patient. In another patient, residual cyst membrane seen intraoperatively and radiologically led to recurrence 18 months postoperatively. No mortalities or permanent morbidities occurred., Conclusions: Our high total excision rate and low complication profile are in concordance with the recent reports of endoscopic resection of colloid cysts. The rotational technique for the endoscopic transforaminal approach is highly effective and a safe alternative to the bimanual dissection technique., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Endoscopic treatment of middle fossa arachnoid cysts is an alternative option to microsurgical fenestration and shunting procedures. The procedure is minimally invasive and obviates the morbidity of craniotomy and shunting., Methods: Operative charts and videos of patients undergoing endoscopic fenestration of middle fossa arachnoid cysts were retrieved from the senior author's database of endoscopic procedures and reviewed. Description of the surgical techniques was then formulated., Conclusions: Endoscopic fenestration of middle fossa arachnoid cysts entails communicating the cyst cavity to the basal cisterns via multiple fenestrations that should be made as large as possible with care to avoid injury of the juxtaposed neurovascular structures.

Background: Adult idiopathic membranous obstruction of the foramen of Monro is an extremely rare condition that can be effectively treated with endoscopic foraminoplasty. A unilateral or bilateral foraminoplasty is performed if one or both of the foramina of Monro are obstructed, respectively. Endoscopic septum pellucidotomy is usually used in combination with the foraminoplasty., Methods: The operative chart and video of one of our patients undergoing endoscopic treatment for adult idiopathic membranous obstruction of the foramen of Monro were retrieved from our database and reviewed. A description of the surgical technique was then formulated., Conclusions: The surgical technique of endoscopic foraminoplasty plus septum pellucidotomy for adult idiopathic membranous obstruction of the foramen of Monro is described.

Background: Endoscopic excision of colloid cysts is currently well established as a minimally invasive and highly effective technique that is associated with less morbidity in comparison to microsurgical resection., Methods: Operative charts and videos of patients undergoing endoscopic colloid cyst excision were retrieved from the senior author's database of endoscopic procedures and reviewed. This revealed nine trans-foraminal and three trans-septal procedures. Description of the surgical techniques was then formulated., Conclusions: Variation of the technique is based on the specific patho-anatomical features of the colloid cyst being resected. For the trans-foraminal approach, we think that the rotational technique is associated with a more complete removal of the cyst wall and consequently lower recurrence rate.

An overview of the development of neuroendoscopy at the neurosurgery department, Ibn Sina Hospital in Kuwait, is presented with an outline of difficulties and obstacles faced by the field until it reached its current status. The factors and solutions that helped us overcome these problems are also elaborated on. After a modest beginning few years ago, endoscopic skull base procedures, intraventricular neuroendoscopy, and spinal endoscopy are regularly performed in the department. Although neuroendoscopy is not per se a neurosurgical subspecialty, it is an area that requires special training. Achieving an appropriate level of care necessitates these highly trained neurosurgeons to collaborate together and with other specialties to create teamsgeared towards offering such treatment options topatients. Importantly, a multitude of essential facilities should be available to make such a pattern of practice possible. In our experience, this was made possible through continued efforts that have finally paid off and gradually led to a complete shift of the face of neuroendoscopic practice in our department. Our future endeavors aim at further development of neuroendoscopy in the department to create a center of excellence., (Copyright © 2016. Published by Elsevier Inc.)

Background: Shunts are generally associated with a smaller post-treatment ventricular size in comparison to endoscopic third ventriculostomy (ETV)., Methods: To determine whether such a difference in ventricular size has neurocognitive implications, we reviewed the current literature pertaining to the (1) neurocognitive sequelae of hydrocephalus, (2) neurocognitive outcome after ETV, (3) extent of reversal of neurocognitive changes associated with hydrocephalus after shunting, and (4) data on correlation between post-treatment ventricular volume and neurocognitive outcome after ETV., Results: Collectively, the results of the available studies should call into question the correlation between the residual postoperative ventricular volume and neurocognitive outcome., Conclusion: The available literature is so far in support of ETV as a valid and effective treatment modality in hydrocephalic patients. No sufficient evidence is available to justify resorting to shunting on the premise that it is associated with a better neurocognitive outcome.

Background: Lumbar microendoscopic discectomy (MED) is a minimally invasive transmuscular approach that combines standard lumbar microsurgical techniques with endoscopy. MED advantages include reduced tissue trauma, direct visualization of the nerve root and disc disease, and allowing bony decompression in cases with spinal or lateral recess stenosis., Methods: Operative charts and videos of patients undergoing MED were retrieved from our database and reviewed. A description of the surgical technique was then formulated., Conclusions: The surgical technique of MED is described and is essentially similar to conventional microdiscectomy. Some modifications are, however, necessary owing to the difference between microscopic and endoscopic views.

Background: Although the ventricular size is significantly reduced after endoscopic third ventriculostomy (ETV) in most successfully treated patients, ventricular size reduction is not always seen after a successful ETV. Practical and reliable radiologic parameters are still needed to assess the clinical success of an ETV., Methods: We retrieved the clinical and radiologic data of patients who underwent an ETV. Patients with the following criteria were included: (1) preoperative magnetic resonance imaging studies available, (2) postoperative magnetic resonance imaging studies done within the first 2 postoperative weeks, and (3) the infundibular recess clearly visible on preoperative and postoperative sagittal magnetic resonance imaging. Preoperative and postoperative measurements of the angle of the infundibular recess of the third ventricle were performed on midsagittal T1-weighted, T2-weighted, fast imaging employing steady-state acquisition, or constructive interference in steady state images., Results: The extent of reduction of the infundibular recess angle predicted the clinical outcome of ETV during the early postoperative period with a high degree of accuracy. The average reduction was about 48% in successful procedures versus only 15% in failed procedures., Conclusions: The degree of reduction of the angle of the infundibular recess of the third ventricle correlated with the amount of third ventricular decompression after ETV. Most importantly, such a reduction was noted to occur during the early postoperative period when radiologic changes are less pronounced. Assessment of change in infundibular recess angle measurement is easy to perform and may prove helpful in cases with no clear-cut clinical evidence of success of ETV., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: The aim of this study is to document the dynamic behavior of a choroid plexus cyst of the third ventricle. Although these lesions may float freely within the ventricle leading to intermittent obstruction of the cerebrospinal fluid (CSF) circulation at variable points in a single patient, such a phenomenon has only been documented using cranial ultrasonography and was never observed intraoperatively., Methods: We endoscopically treated a case of third ventricular choroid plexus cyst in a 9-year-old boy who presented with headaches and disturbed conscious level. He underwent a transventricular approach through a single burr hole., Results: During the procedure, the cyst was noted to intermittently herniate into the lateral ventricle and recede back through the foramen of Monro. Endoscopic ablation of the cyst was achieved and followed by endoscopic third ventriculostomy (ETV). The patient made an excellent recovery after the procedure., Conclusions: We were able to endoscopically observe the dynamic behavior displayed by a choroid plexus cyst of the third ventricle. To the best of our knowledge, intraoperative documentation of the obstruction of the CSF pathway by a single choroid plexus cyst that intermittently herniates through the foramen of Monro and back into the third ventricular cavity has not been previously demonstrated neither microsurgically nor endoscopically.

Background: Endoscopic biopsy of brain tumors is an important part of the armamentarium of management of intra- and periventricular tumors that is generally considered an acceptable and, in some situations, a preferred method for tissue sampling. The diagnostic yield of the procedure has been variably reported. Technical aspects of the procedure should undoubtedly reflect on its success rate and accuracy. Such impact on diagnostic yield of endoscopic brain biopsy is infrequently discussed in the literature., Methods: A search of the medical literature was conducted for publications on endoscopic brain biopsy. These reports were analyzed regarding the various technical aspects., Results: In the 43 publications analyzed, lenscopes were exclusively used in 22 reports and a tissue diagnosis was possible in 362 out of 387 endoscopic biopsies with a diagnostic yield of 93.54%. Only fiberscopes were used in 8 reports and a tissue diagnosis was possible in 100 out of 132 endoscopic biopsies with a diagnostic yield of 75.76%. The diagnostic yield in the mixed and unspecified groups was 88.95 and 88.04%, respectively. Very few details on the histopathological methods and tumor molecular genetics could be found., Conclusion: Endoscopic biopsy of brain tumors has a higher diagnostic yield when lenscopes are used. Neuronavigation seems to add to the diagnostic accuracy of the procedure. Studies detailing molecular genetic features of biopsied tumors are necessary in the future.

Background: Colloid cysts are usually located at the rostral part of the third ventricle in proximity to the foramina of Monro. Some third ventricular colloid cysts, however, attain large sizes, reach a very high distance above the roof of the third ventricle, and pose some challenges during endoscopic excision. These features led to the speculation that for such a pattern of growth to take place, the points of origin of these cysts should be at areas away from the foramina of Monro at which some anatomical "windows" exist that are devoid of compact, closely apposed forniceal structures., Methods: A review of the literature on anatomical variations of the structures in the vicinity of the roof of the third ventricle and on reported cases with similar features was conducted., Results: Colloid cysts may grow vertically up past the roof of the third ventricle through anatomical windows devoid of the mechanical restraint of the forniceal structures., Conclusion: Some anatomical variations of the forniceal structures may allow unusually large sizes and superior vector of growth of a retro- or post-foraminal colloid cyst. Careful preoperative planning and knowledge of the pertinent pathoanatomy of these cysts before endoscopic excision is very important to avoid complications.

Background: Johannes Vermeer of Delft [1632-1675] was one of the greatest Masters of the Dutch Golden Age who was intensely preoccupied with the behavior of light and other optical effects and was entitled "The Master of Light". He fastidiously attended to the subtleties of visual expression through geometry, composition, and precise mastery of the rules of perspective. It has been our impression that some visual similarity does exist between neuroendoscopic images and some of Vermeer's paintings. Such a relation could be explained by the fact that optical devices are utilized in producing both types of display., Methods: We reviewed the pertinent medical and art literature, observed some video clips of our endoscopy cases, and inspected digital high resolution images of Vermeer's paintings in order to elaborate on shared optical phenomena between neuroendoscopic views and Vermeer's paintings., Results: Specific optical phenomena are indeed shared by Johannes Vermeer's works and neuroendoscopic vision, namely light and color effects as well as the rules of perspective., Conclusion: From the physical point of view, the possibility that a camera obscura inspired Vermeer's artistic creation makes the existence of a visual link between his paintings and the endoscopic views of the intracranial cavity comprehensible.

Background: In 1900, Joseph Blake described a transient posterior evagination of the tela choroidea of the fourth ventricle in the normal 130-day old human embryo. He was the first to recognize and fully elucidate on the real nature of the foramen of Magendie as an aperture, which develops within a saccular expansion of the embryonic fourth ventricular cavity. The persistence of this temporary fourth ventricular outpouching into the postnatal period and its significance either as separate entity or as an entity within the Dandy-Walker continuum has over the years been one of the most controversial topics in both neurosurgical and neuroradiological literature., Methods: A search of the medical literature was conducted for publications addressing the historical, embryological, and neuororadiological features as well as the clinical presentation and management of persistent Blake's pouch., Results: The literature on the various features of Blake's pouch cyst has limited areas of consensus between various authors., Conclusion: Blake's pouch cyst is a rare entity that is thought to belong to the Dandy-Walker continuum. It has a variable clinical presentation and when symptomatic can be treated with an endoscopic third ventriculostomy or shunting.

John Edwin Scarff (1898-1978) was one of the pioneers of neuroendoscopy and the head of the Department of Neurological Surgery at Columbia University in New York from 1947 to 1949. In this article, we highlight the pioneering and longstanding efforts of John E. Scarff in support of endoscopic choroid plexus coagulation. These efforts represent an important part of the rich history of neuroendoscopy and a legacy to which the current procedure owes a great credit.

Background: Narrowing of the intervertebral foramen for C5 root and a larger superior articular process in myelopathic patients with postlaminoplasty motor dominant C5 radiculopathy has been reported. We investigated whether the C4-5 foraminal dimensions and surface area in patients with cervical spondylotic myelopathy are universally smaller than the intervertebral foramina at other cervical levels., Methods: The study population consisted of 44 consecutive patients (sex: 24 males and 20 females), averaging 55.7 years of age (range 42-84) years who presented with clinical features suggestive of cervical spondylotic myelopathy. Using computed tomography (CT) imaging, we prospectively compared height, transverse diameter, and surface area of the C4-5 foramen to those of C3-4, C5-6 and C6-7 foramina of the same side in the whole study population as well as in male and female patients., Results: In the whole study population at C4-5 intervertebral foramen the mean foraminal height was 8.37 ± 1.3 mm on the right and 8.85 ± 1.16 mm on the left; and the mean foraminal transverse diameter on the right was 4.97 ± 1.35 mm and 5.14 ± 1.16 mm on the left. No statistically significant difference was found between the measurements in the whole study population at various levels, between or within male and female patient groups., Conclusion: C4-5 intervertebral foramen is not uniformly smaller in patients with cervical spondylotic myelopathy.

Background: The list of pineal region tumors comprises an extensive array of pathological entities originating within one of the most complex areas of the intracranial cavity. With the exception of germ cell tumors, microsurgical excision is still nowadays the mainstay of management for most pineal region tumors., Methods: A search of the medical literature was conducted for publications addressing surgical options for management of pineal region tumors., Results: The infratentorial supracerebellar and the occipital transtentorial approaches are currently the most frequently used approaches for pineal region tumors. Endoscopic tumor biopsy with simultaneous endoscopic third ventriculostomy has emerged as a minimally invasive and highly effective strategy for initial management since it addresses the issue of tissue diagnosis and offers a solution for the associated hydrocephalus frequently encountered in these patients. Endoscope-assisted microsurgery and purely endoscopic excision have been reported in few reports and are likely to be more utilized in the future., Conclusion: Preoperative planning is very crucial and should most importantly be individualized according to the anatomical features of the lesion and structures encountered during the procedure.

Rosai-Dorfman disease (RDD) is a rare but well-recognized idiopathic histioproliferative disease affecting the systemic lymph nodes. It is characterized by an unusual proliferation of histiocytic cells. Intracranial localization is a rare manifestation of RDD. The clinical and radiological differentiation from meningiomas is difficult, and can only be achieved after histological examination. This entity should be considered in the differential diagnosis of dural based lesions mimicking meningioma. We report 2 cases of isolated intracranial RDD. The first patient had a large frontal lesion in addition to smaller multiple intracranial lesions. The second patient had only one parasagittal lesion. The diagnosis was confirmed on histopathological examination after surgical excision. The pertinent literature is also reviewed.

Aim: Iatrogenic vertebral artery (VA) injury during ventral approaches to the subaxial cervical spine ranges from 0.22% to 2.77%. Evaluation of the extent of safe lateral working distance before the V2 segment of the VA is reached can be helpful to avoid this complication., Material and Methods: In 100 patients (48 males and 52 females) axial computed tomographic scanning was used to measure the distance from the medial border of longus colli muscle (LCM) to the medial border of the foramen transversarium along the anterior border of the vertebral body at each level from C3-4 down to C6-7. The arithmetic mean of the 2 measurements at the upper and lower end-plates of the corresponding level was considered representative of the safe lateral working distance at this level. Statistical significance was set as P value < 0.001., Results: No statistically significant difference was found between the measurements in the whole study population at various levels or between subgroups. A gradual increase in the distances was noticed from C3-4 down to C6-7 level in all subgroups except for spondylotic males., Conclusion: This study offers useful morphometric data that can help the surgeon avoid VA injury during anterior procedures to the subaxial cervical spine.