Diagnostic value of the CSF levels of D-Lactate and pro-inflammatory cytokines (TNF-alpha, IL-6, IL-8 and IL-17) in the patients with suspected nosocomial meningitis.

INTRODUCTION: This study aims to determine the diagnostic value of IL-6, IL-8, IL-17, TNF-α and D-lactate levels in the cerebrospinal fluid (CSF) in nosocomial meningitis. METHODS: CSF levels of cytokines and D-lactate were compared across 29 episodes who were diagnosed with nosocomial meningitis, 38 episodes with pleocytosis but without meningitis and 54 control subjects. RESULTS: CSF levels of IL-6, IL-8, and D-lactate were higher in the group with nosocomial meningitis compared to the control group and to the group with pleocytosis without meningitis (p<0.05). For the levels of IL-6, when the threshold was considered to be > 440 pg/mL, the sensitivity and specificity were 55.17% and 94.74%, respectively. For IL-8 levels, when the threshold was considered to be >1249 pg/mL, the sensitivity and specificity were 44.83% and 84.21%, respectively. In the patients with nosocomial meningitis, when the threshold of D-lactate levels was considered to be >1.05µmol/mL, the sensitivity and specificity were found to be 75.86% and 63.16%, respectively. In the pleocytosis without meningitis CSF samples and in the CSF samples diagnosed with nosocomial meningitis, the highest AUC was calculated for triple combination model of IL-6, IL-8, and D-lactate levels (AUC= 0.801, p<0.001), and double combination model IL-6 and IL-8 (AUC= 0.790) (p<0.001). CONCLUSION: In our study, we have concluded that IL-6, IL-8 and D-lactate levels could be diagnostic markers for nosocomial meningitis.

Comparison of the effects of medical and surgical treatments in giant prolactinoma: a single-center experience.

PURPOSE: Giant prolactinomas, which have extremely large sizes and high prolactin (PRL) values, are rarely seen. Although medical therapy is effective, surgical treatment is more frequently applied due to slightly lower response rates and compression symptoms. This study aimed to compare the medical and surgical treatment results in giant prolactinomas. METHODS: Thirty-nine patients who were followed up in our center for giant prolactinoma were included in the study, and the response rates of the patients were evaluated after the medical and surgical treatments. The treatment responses were compared in terms of tumor volume, PRL level, visual field, and pituitary function. RESULTS: The outcomes of the 66 treatment periods (medical n = 42; surgical n = 24) in 39 patients (mean age, 47.2 years; men, 89.7%) were evaluated. The most common presentations were hypogonadism and visual defects. The mean longest tumor diameter at diagnosis was 52.2 ± 11.8 mm, and the median PRL levels were 5000 ng/mL. PRL level normalization was achieved in 69% with medical therapy, and a curative response was obtained in only two patients with surgery. Tumor volume reduction was 67% (no cure) in the medical and 75% (13% cure) in the surgical groups (p = 0.39). Improvement of visual field was 70.8% in the medical and 84.2% in the surgical group (p = 0.12). CONCLUSION: In our study, it was observed that medical therapy was effective and safe in patients with giant prolactinomas. The use of surgical treatment should be limited to prolactinomas with compression or post-resistance to medical treatment in serious cases.

Statistical Shape Analyses of the Brainstem in Chiari Patients.

AIM: To ascertain whether the brain stem?s shape differs in patients with syrinx and without syrinx in cases with Chiari malformation Type I (CM-1), relative to healthy controls. MATERIAL AND METHODS: Data on marked brainstem regions were obtained from 2D digital image files. Generalized Procrustes analysis was used to evaluate shape differences among patients with syrinx, patients without syrinx, and healthy controls. Shape deformations among groups were examined by Thin Plate Spline (TPS) analysis. RESULTS: According to the brain stem shape, there were differences between patients with syrinx and controls, and between patients without syrinx and controls. High-level deformations were also observed among the groups. CONCLUSION: In the present study, the presence of shape deformations in Chiari patients? brainstem was demonstrated. This is the first study using a landmark-based geometrical morphometric method to demonstrate the shape difference in Chiari patients? brainstem.

Resection of a Lower Clival Meningioma via Posterolateral Approach: Two-Dimensional Operative Video.

Objectives This study aimed to demonstrate resection of a craniovertebral junction (CVJ) meningioma via the posterolateral approach. Design The study is designed with a two-dimensional operative video. Setting This study is conducted at department of neurosurgery in a university hospital. Participants A 50-year-old woman who presented with lower cranial nerve findings due to a left-sided lower clival meningioma ( Fig. 1 ). Main Outcome Measures Microsurgical resection of the meningioma and preservation of the neurovascular structures. Results The patient was placed in park-bench position and a left-sided retrosigmoid suboccipital craniotomy, followed by C1 hemilaminectomy and unroofing the lip of the foramen magnum, was performed. The dural incision extended from the suboccipital region down to the posterior arch of C2 ( Fig. 2 ). The arachnoid overlying the tumor was incised, revealing the course of the cranial nerve (CN) XI on the dorsolateral aspect of the tumor. The left vertebral artery (VA) was encased by the tumor which was originating from the dura below the jugular foramen. The mass was resected in a piecemeal fashion eventually. At the end of the procedure, all relevant cranial nerves and adjacent vascular structures were intact. Postoperative magnetic resonance imaging (MRI) confirmed total resection and the patient was discharged home on postoperative day 3 safely. Conclusions Microsurgical resection of the lesions of the CVJ are challenging as this transition zone between the cranium and upper cervical spine has a complex anatomy. Since adequate exposure of the extradural and intradural segments of the VA can be obtained by the posterolateral approach, this approach can be preferred in cases with tumors anterior to the VA or when the artery is encased by the tumor. The link to the video can be found at: https://youtu.be/d3u5Qrc-zlM .

A neurosurgical assessment of the blood supply in the optochiasmatic system: a cadaveric-anatomic study.

The chiasmal and subchiasmal surfaces are of critical importance in connection with the performance of surgical procedures owing to the critical blood supply to these areas. Recently, the perforating arteries providing the blood to the optic nerves and chiasm have gained attention as they significantly affect the morbidity from surgical approaches. Intraoperative preservation of these perforating arteries is considered critical to prevent further visual loss. Thirty autopsy specimens, including the optic apparatus, were examined for their perforating arteries feeding the optic chiasm and optic nerves. The optic nerves and chiasmal surfaces were divided into four zones based on the presence and numbers of perforating arteries as anterior superior-posterior superior surfaces and anterior inferior-posterior inferior surfaces. The superior surface of the optic chiasm was supplied by the A1 segments of the bilateral anterior cerebral arteries and by the perforating arteries originating from the anterior communicating artery. On the other hand, the inferior surface of the optic chiasm was fed by the bilateral posterior communicating arteries and by the supraclinoidal segments of the bilateral carotid arteries. We demonstrated the anatomical involvement of a large number of nourishing arteries in feeding the optic apparatus related to the perforating arteries by classifying them into zones based on the surgical approaches, which has been rarely reported in the literature.

The anatomic variations and surgical windows among optic chiasm/nerves and carotid arteries in the sellar region play a role in choosing the best surgical approaches: A Cadaveric study / Las variaciones anatómicas y las vías de acceso quirúrgico en el quiasma, los nervios ópticos y las arterias carótidas de la región selar influyen en la elección de los mejores abordajes quirúrgicos: un estudio en cadáveres

OBJECTIVE: Understanding the relationship between the carotid artery, optic nerve and the anterior clinoid process is the basis of surgical approaches performed in the subchiasmal region. The location of the optic chiasm, the length of the optic nerves, and the distance and angle between the optic nerves determine the route of surgical approaches. We have determined the types of optic chiasm to study the relationship between vascular and neural structures in this region. MATERIALS AND METHODS: Thirty autopsy specimens were investigated at the Bursa Forensic Medicine Institute for optic chiasm types and the relationship between the neural and vascular anatomical structures of the sellar-parasellar and subchiasmal region was examined between June 2016 and November 2016. RESULTS: In this study, 4 prefix types (13%), 6 postfix types (20%), and 20 central types (67%) of chiasm were defined. Furthermore, we measured this angle between two optic nerves, which indirectly shows the location of chiasm according to the diaphragma sellae, and then detected the mean value of this angle as 87.1 ± 11.6°. The "limit" value to designate a chiasm as prefix was measured in the current study as ≥ 101.1°. The angle between optic nerves ranged from a mean value of 69.9 ± 3.7° in 6 cases with postfix chiasm, to a mean value of 104.0±2.1° in 4 cases with prefix chiasm and a mean value of 88.8 ± 6.7° in 20 cases with central chiasm. CONCLUSIÓN: In this study, we showed that the relationship among optic chiasma types, optic nerves and bony and vascular structures around the sellar area was effective at determining the surgical approach to this región

OBJETIVO: Comprender la relación entre la arteria carótida, el nervio óptico y la apófisis clinoides anterior es la base de los tratamientos quirúrgicos realizados en la región subquiasmática. La ubicación del quiasma óptico, la longitud de los nervios ópticos, y la distancia y el ángulo entre dichos nervios determinan la vía de acceso quirúrgico. Hemos determinado los tipos de quiasma óptico para estudiar la relación entre las estructuras vasculares y neurales en esta región. MATERIALES Y MÉTODOS: Entre junio y noviembre de 2016, se analizaron 30 muestras de autopsia en el Instituto de Medicina Legal de Bursa (Turquía) para determinar los tipos de quiasma óptico, y examinar la relación entre las estructuras anatómicas neurales y vasculares de las regiones selar-paraselar y subquiasmática. RESULTADOS: En este estudio, se definieron 4 casos de quiasma prefijado (13%), 6 de quiasma posfijado (20%) y 20 de quiasma central (67%). Además, medimos el ángulo entre 2 nervios ópticos que muestra indirectamente la ubicación del quiasma según el diafragma selar, y luego detectamos el valor medio de este ángulo (87,1 ± 11,6°). El valor «límite» para designar un quiasma como «prefijado» se midió en el estudio actual como ≥ 101,1°. El valor medio del ángulo entre los nervios ópticos osciló entre 69,9 ± 3,7° en los 6 casos de quiasma posfijado, 104,0 ± 2,1° en los 4 casos de quiasma prefijado y 88,8 ± 6,7° en los 20 casos de quiasma central. CONCLUSIÓN: En este estudio, pusimos de manifiesto que la relación entre los tipos de quiasma óptico, los nervios ópticos y las estructuras óseas y vasculares alrededor del área selar fue eficaz para determinar el acceso quirúrgico en esta región

Retrosigmoid Transtentorial Resection of a Petroclival Meningioma: 2-Dimensional Operative Video.

In this video, we aimed to demonstrate retrosigmoid-transtentorial resection of a 4.5 × 4 × 4.5 cm3 left-sided petroclival meningioma compressing the brainstem in a 62-yr-old male who presented with decreased hearing on the left and imbalance. The patient was placed in park-bench position and a left-sided suboccipital craniotomy was performed. The mass was severely compressing the brainstem as well as the cranial nerves V, VI, VII, and VIII while IV was encased by the tumor. The circumferential dissection of the tumor was facilitated while the surgical corridor and exposure were enlarged by incising the tentorium. Uneventfully, the meningioma was resected in piecemeal fashion as it was not coming out easily with the ultrasonic aspirator. All relevant cranial nerves and adjacent vascular structures were protected. Early postoperative CT scan demonstrated changes due to the surgery and resolution of the compression on the brainstem. The patient made excellent recovery and he was discharged home on postoperative day 4 safely. Petroclival meningiomas are one of the most challenging tumors for neurosurgeons due to their close proximity to the vascular structures, cranial nerves as well as the brainstem. The retrosigmoid approach provides a direct route during microsurgical resection of these tumors. By incising the tentorium, the corridor can be widened while addressing the supratentorial portion of the tumor with relative ease.

The anatomic variations and surgical windows among optic chiasm/nerves and carotid arteries in the sellar region play a role in choosing the best surgical approaches: A Cadaveric study.

OBJECTIVE: Understanding the relationship between the carotid artery, optic nerve and the anterior clinoid process is the basis of surgical approaches performed in the subchiasmal region. The location of the optic chiasm, the length of the optic nerves, and the distance and angle between the optic nerves determine the route of surgical approaches. We have determined the types of optic chiasm to study the relationship between vascular and neural structures in this region. MATERIALS AND METHODS: Thirty autopsy specimens were investigated at the Bursa Forensic Medicine Institute for optic chiasm types and the relationship between the neural and vascular anatomical structures of the sellar-parasellar and subchiasmal region was examined between June 2016 and November 2016. RESULTS: In this study, 4 prefix types (13%), 6 postfix types (20%), and 20 central types (67%) of chiasm were defined. Furthermore, we measured this angle between two optic nerves, which indirectly shows the location of chiasm according to the diaphragma sellae, and then detected the mean value of this angle as 87.1±11.6°. The "limit" value to designate a chiasm as prefix was measured in the current study as ≥101.1°. The angle between optic nerves ranged from a mean value of 69.9±3.7° in 6 cases with postfix chiasm, to a mean value of 104.0±2.1° in 4 cases with prefix chiasm and a mean value of 88.8±6.7° in 20 cases with central chiasm. CONCLUSION: In this study, we showed that the relationship among optic chiasma types, optic nerves and bony and vascular structures around the sellar area was effective at determining the surgical approach to this region.

Statistical Shape Analysis of Cerebellum in Patients With Chiari Malformation I.

The surgical procedure is viewed as a typical treatment choice for patients with Chiari malformation (CM). Decompression is the preferred method for surgery, but it is not always possible to understand whether decompression has been successful especially in an early period. The present study focuses on investigating the shape differences in the cerebellums of Chiari patients compared with healthy controls, and to assess the clinical application of this situation whether if present. The MRI scans were reviewed retrospectively. Cerebellar data were obtained from the digital images and 9 anthropometric landmarks were marked on each image. Shape difference was assessed by performing Generalized Procrustes analysis. The cerebellar shape deformation from control to the patient was evaluated performing the Thin Plate Spline approach. There is a statistically significant cerebellar shape difference between groups. Highest deformation was determined at the cerebellar tonsillar inferior area, posterior of the uvula, and anterior of inferior medullary velum. The present study demonstrated cerebellar shape differences in CM I patients using a landmark-based geometric morphometric approach, considering the topographic distribution of cerebellum for the first time.

Anatomical aspects of optic nerve decompression in transcranial and transsphenoidal approach.

PURPOSE: The proximal portion of the optic nerve is quite prone to injury at the entrance of the optic foramen by tumoral or traumatic pathologies. As a result, it is important to show which way and which part we can effectively and safely decompress the pathologies affecting the optic nerves. In this study, we compared the decompression of the proximal segment of the optic canal Likewise, we investigated the anatomy and histopathology of the opticocarotid region from below and above. MATERIALS AND METHODS: A total of 30 adult sellar and parasellar samples were extracted from human cadavers. Anatomical dissection and histological examination were performed from transcranial and transsphenoidal ways. The walls of the proximal optic canal were evaluated with an operating microscope and endoscope. The relationship between the optic canal, the internal carotid artery, and the optic nerve were qualitatively and quantitatively examined. RESULTS: Similar rates of circular optic canal decompression were achieved by each approach; however, by means of decompression, the transsphenoidal approach was superior for the inferior and medial portions of the optic nerve and transcranial approach was superior for the superior and lateral portions and also more appropriate for optic nerve mobilization. CONCLUSION: This is one of the first studies to reveal the ways of the decompression of the proximal optic canal by transcranial and transsphenoidal approaches. According to this study, the medial and inferior proximal portions of the optic nerves are histologically more prone to injury caused by traction or compression. Transcranial or transsphenoidal approach should be preferred according to the location of the pathology and anatomical and histological characteristics of this region.

Leptomeningeal dissemination and vertebral bone involvement in a child with pilocytic astrocytoma.

In low-grade glioma, metastasis is rarely seen. Few cases of leptomeningeal dissemination have been reported in children. Vertebral bone metastasis has not been reported so far. Herein is described the case of a pediatric patient with the diagnosis of pilocytic astrocytoma, and leptomeningeal dissemination detected at the time of diagnosis, who then received radiotherapy and chemotherapy upon development of vertebral bone metastasis during treatment.

Transnasal Transsphenoidal Surgical Method in Pediatric Pituitary Adenomas.

AIM: To evaluate the clinical outcome in a 13-year consecutive series of children operated for pituitary adenomas with transnasal transsphenoidal surgery. METHODS: All patients <18 years who were operated on at our center by transsphenoidal surgery for pediatric pituitary adenomas were included in the study. Clinical features, hormonal profile, radiology, surgical approach, results and complications were analyzed. RESULTS: Eighteen patients (90%) had functional pituitary adenomas and 2 (10%) patients had nonfunctional pituitary adenoma. The most common type was prolactin-secreting adenoma (n = 12), followed by corticotropinoma (n = 4), growth hormone-secreting adenoma (n = 2), and nonfunctioning adenoma (n = 2). Prolactin-secreting adenomas in children occurred more commonly with suprasellar expansion than did other adenomas. CONCLUSION: Transsphenoidal surgery was effective for decompression of suprasellar extension and relieved the chiasmal compression immediately. Prolactin-secreting tumors required postoperative medical therapy for persistently elevated prolactin levels.

The artery of Percheron revisited: a cadaveric anatomical study.

BACKGROUND: The artery of Percheron (AOP) is a single thalamoperforating arterial trunk that provides bilateral supply to the paramedian thalami and the rostral midbrain. As this rare anatomical variant artery may be involved in endovascular procedures or encountered surgically during basilar terminus aneurysms, the present study was warranted. METHOD: Thirty-four adult (20 male and 14 female) formalin-fixed cadaveric brains underwent dissection of the 68 posterior cerebral arteries. Observations were made of the presence and the variations of the thalamoperforating arteries as well as the presence of the AOP. FINDINGS: Thalamoperforating arteries arose from the superior or posterior surfaces of the P1 segment at a mean of a 1.87 mm (range, 0.39-5.25 mm) distance from the basilar apex and entered the brain through the posterior perforated substance. The average number was 4.25 (range 1-9), and the mean diameter was 0.73 mm (range 0.46-1.16 mm). Thalamoperforating arteries were classified into four different types according to their origin at the P1 segment: type I (bilateral multiple, n = 19), 55.8 %; type II (unilateral multiple, unilateral single, n = 4), 11.7 %; type III (bilateral single, n = 7), 20.5 %; type IV [one side with a single branch, the other side with no branches (the AOP), n = 4], 11.7 %. In three separate specimens with ruptured basilar artery aneurysms, the origin of the thalamoperforating arteries was incorporated not only into the posterior aspect of the aneurysm neck but also into the fundus. CONCLUSIONS: In about one tenth of cases the possibility of the presence of a single arterial trunk that supplies the two paramedian thalamic territories should be taken into consideration during treatment planning of basilar terminus aneurysms. Furthermore, our data show that the thalamoperforating arteries may take off from both the aneurysm neck and the fundus.

Anatomical restrictions in the transsphenoidal, transclival approach to the upper clival region: a cadaveric, anatomic study.

OBJECTIVE: Tumours in the clival region are difficult to remove surgically. Before the 1970s, clival tumours had very high mortality and morbidity rates. METHODS: An anatomic dissection was performed on 24 spheno-occipital bone blocks obtained from 28 adult cadavers. The internal carotid artery, paraclival carotid tubercle, sixth cranial nerve and dorsum sellae in the upper clival region were analyzed qualitatively and quantitatively. For the histological evaluation, 4 samples were decalcified and sagittal sections were cut. From the eight blocks obtained, 32 incisions were made in the axial plane, and the tissue was analyzed. RESULTS: Using microscopy, a clival recess was clearly identified in 15 of the 24 (62.5%) samples. Paraclival carotid tubercles were observed in 19 (79.16%) of the samples. In the upper clival and petroclival region, the sixth cranial nerve had directional changes at the dural porus, the petrous apex and the lateral wall of the cavernous segment of the internal carotid artery. At the dorsum sellae level, the distance between the medial surfaces of both internal carotid arteries was a mean of 15.33 ± 2.12 mm. This distance at the pharyngeal tubercle was a mean of 38.95 ± 4.67 mm. On all the histological sections, the distance of the sixth cranial nerve from the dural porus to the cavernous sinus was within the basilar plexus, along with the subarachnoid membranes around it. On the petrous apex level, the sixth cranial nerve was fixed to the petrous apex and the internal carotid artery with connective tissue formed by dense collagen fibres. The sixth cranial nerve and the internal carotid artery are tightly surrounded by dense collagen connective tissue, and the relative proximity between the carotids on the dorsum sellae level can be easily damaged during the transsphenoidal-transclival approach. Similarly, due to the ligamentous fixation on the dural porus and the petrous apex surfaces, there is a high risk of injury to the carotid artery and sixth cranial nerve. CONCLUSION: This study determines the relationship between the sixth cranial nerve and the internal carotid artery at the upper clivus and to provide morphologic details that is essential for the risks of transclival surgery.

Anatomical aspects in the transsphenoidal-transethmoidal approach to the optic canal: an anatomic-cadaveric study.

BACKGROUND: Determining anatomic landmarks during a transsphenoidal-transethmoidal approach to the optic canal region is of critical importance. METHODS: Sella-parasella sphenoid bone blocks were extracted from adult cadavers. Anatomic dissections were performed in the optic canal region using a surgical microscope in 30 samples. Quantitative measurements were done using photographic techniques. For histological evaluation, coronal and longitudinal cross-sections were taken from the bilateral optic canal in seven decalcified samples. RESULTS: Optic protuberance (OP), carotid protuberance (CP), medial opticocarotid recess (MOCR) and lateral opticocarotid recess (LOCR) were defined as lateral landmarks determining the width of the opening in the extended transsphenoidal-transethmoidal approach. Among all anatomic markers, LOCR was the most determinant lateral marker with tubercular recess the most prominent central marker. OPs showing the optic canal direction and inter-recessal sulci had similar distinguishing rates in the sphenoid sinus base. Inter-recessal sulci formed by OPs and CPs were observed between MOCR and LOCR in most samples. In histologic sections, the dural sheath was thicker inferolaterally to the optic nerve compared to superiorly and medially; collagen arrangement was dense and irregular. CONCLUSION: Although LOCRs and tubercular recesses are safe and prominent markers in extended transsphenoidal-transethmoidal approaches, other anatomic markers should also be taken into consideration to perform an efficient optic canal approach and optic canal decompression. Other factors for safe dissection are the length of the optic canal, bone thickness, adherence of dural structures and the course of the intradural ophthalmic artery.

Surgical limits in transnasal approach to opticocarotid region and planum sphenoidale: an anatomic cadaveric study.

BACKGROUND: The significance of medial and lateral opticocarotid recesses and the planum sphenoidale region in skull base pathologies for the transsphenoidal-transplanum approach were evaluated. METHODS: The sphenoid bone block samples were extracted from adult cadavers. Dissections and measurements in the opticocarotid and planum sphenoidale regions were performed in 29 samples using a surgical microscope. For histologic evaluation, oblique sections through the bilateral opticocarotid regions were obtained and examined in eight samples. RESULTS: Optic, carotid prominences, and medial and lateral opticocarotid recesses can be identified as lateral markers intraoperatively to the extent of the exposure. The lateral opticocarotid recess was observed to be prominent in all samples. In all samples, the groove formed by optic and carotid prominences between the medial and lateral opticocarotid recesses was seen. This groove was designated the inter-recess sulcus. In the transsphenoidal-transplanum approach, the area needed for a reliable bone resection was measured as a mean of 237.32 ± 30.96 mm(2). The mean angle between optic nerves was 115.41 ± 18.39 degrees. The mean anteroposterior length of the planum sphenoidale was 14.84 ± 1.52 mm. In histologic sections, collagenous ligaments between the anterior part of cavernous sinus and the adventitia layer of internal carotid artery were more frequent and regular than the inferior part of optic nerve. CONCLUSIONS: The lateral opticocarotid recess is a reliable and persistent indicator for extended transsphenoidal surgery. To approach the opticocarotid region near the internal carotid artery and optic nerve, a careful dissection is needed to minimize surgical injuries to the optic nerve and carotid artery. Other factors determining a reliable bone resection are the anteroposterior length of the planum sphenoidale and the distance and width of the angle between optic nerves. Attention should be given to individual anatomic variations of the region when planning and performing transsphenoidal-transplanum surgery.

Anatomy of the floor of the third ventricle in relation to endoscopic ventriculostomy.

Neuroanatomical structures that form the floor of the third ventricle (FTV) and neighboring tissues are important in the context of third ventriculostomy (TV) procedures. Thorough knowledge of the anatomical and histological organization of the region would be useful in understanding and preventing surgical complications. Taking the third ventricle region as a model, we aimed to simulate TV and make measurements of 23 cadaver brains, as well as perform histological examinations of the third ventricular floor on five cadaver brains. During the endoscopic TV, we examined the degree to which the structures surrounding the FTV were affected by surgical simulation. To make a clinical comparison, the distance between the center of the FTV and the basilar apex was measured on cranial magnetic resonance images (MRIs) of 15 subjects with normal ventricular systems and 15 subjects with moderately enlarged ventricles. Histological examination revealed that the ependymal cells and arachnoid membrane formed the inner and outer surfaces of the third ventricle floor, respectively, whereas the stroma was made up of glial cells exclusively. This region was gliotic and avascular. When cadaver brains with normal and hydrocephalic ventricles were compared, there were significant differences in the distance between the center of the floor and the basilar apex (P < 0.001). On the basis of our study, the optimal site for TV fenestration and balloon inflation is just anterior to the mamillary bodies to avoid injury to neighboring structures.