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Purpose The purpose of the present study was to evaluate contrast enhancement of the infundibular recess in the normal state using heavily T2-weighted 3D fluid-attenuated inversion recovery (FLAIR) (HT2-FLAIR). Methods Twenty-six patients were retrospectively recruited. We subjectively assessed overall contrast enhancement of the infundibular recess between postcontrast, 4-hour (4-h) delayed postcontrast, and precontrast HT2-FLAIR images. We also objectively conducted chronological and spatial comparisons by measuring the signal intensity (SI) ratio (SIR). Chronological comparisons were performed by comparing SI of the infundibular recess/SI of the midbrain (SIRIR-MB). Spatial comparisons were conducted by comparing SI on postcontrast HT2-FLAIR/SI on precontrast HT2-FLAIR (SIRPost-Pre) of the infundibular recess with that of other cerebrospinal fluid (CSF) spaces, including the superior part of the third ventricle, lateral ventricles, fourth ventricle, and interpeduncular cistern. Results In the subjective analysis, all cases showed contrast enhancement of the infundibular recess on both postcontrast and 4-h delayed postcontrast HT2-FLAIR, and showed weaker contrast enhancement of the infundibular recess on 4-h delayed postcontrast HT2-FLAIR than on postcontrast HT2-FLAIR. In the objective analysis, SIRIR-MB was the highest on postcontrast images, followed by 4-h delayed postcontrast images. SIRPost-Pre was significantly higher in the infundibular recess than in the other CSF spaces. Conclusion The present results demonstrated that the infundibular recess was enhanced on HT2-FLAIR after an intravenous gadolinium injection. The infundibular recess may be a potential source of the leakage of intravenously administered gadolinium into the CSF.

BACKGROUND Modified orbitozygomatic craniotomy is characterized by simplicity and wide exposure. The purpose of the present study was to describe a modified orbitozygomatic approach without resecting the zygomatic arch for large parasellar tumor surgeries. METHODS Between April 2016 and December 2019, seven patients with parasellar tumor underwent surgiest with a modified orbitozygomatic approach. Surgical procedures, clinical outcomes, and complications were analyzed. RESULTS This study included 3 meningiomas, 2 pituitary adenomas, 1 chondrosarcoma, and 1 schwannoma. Modified orbitozygomatic craniotomy provides a wider surgical freedom in the opticocarotid and prechiasmatic cistern than frontotemporal craniotomy without orbitotomy, Total, subtotal, and partial resections were achieved for 3, 2, and 2 patients, respectively. Reasons for partial resections were tight adhesion to the carotid artery and encasing of the carotid artery. Permanent morbidities developed in one patient with 3rd nerve palsy and one patient with hemiparesis. CONCLUSION Modified orbitozygomatic approach can provide the shortest access to the interpeduncular cistern with a minimum brain retraction. Surgeons who experience surgical challenge during the conventional approach for parasellar tumor resection are recommended to learn the modified orbitozygomatic approach.

We describe the anatomical landmarks and surgical feasibility of a novel ‘safe’ brainstem entry zone to approach ventrally placed intra-axial midbrain tumors. The anatomy of the brainstem was specifically studied to evaluate safe surgical entry zone in the midbrain on two formalin fixed silicon injected cadaver head specimens. A novel entry point through the lateral one – fifth of the cerebral peduncle was identified to be ‘safe’ to approach lesions of the ventral midbrain. Three patients, having oculomotor schwannoma, peduncular glioma and a peduncular cavernoma were operated using this safe entry zone. To approach the midbrain, retrosigmoid lateral supracerebellar route was used in two patients and a basal subtemporal avenue was deployed in one patient. On the basis of fine microanatomical dissection on cadavers, a novel entry point through the lateral one-fifth of the cerebral peduncle, 5 mm anterior to the lateral mesencephalic sulcus and approximately 5 mm superior to the fourth nerve was identified. The proposed brainstem entry point traverses the parieto-temporo-occipital pontine fibers and the trajectory is between the corticospinal tracts ventrally and the substantia nigra dorsally. Three patients were operated successfully using the approach. There were no post-operative motor, sensory or extra-pyramidal deficits. The corridor through the lateral one-fifth of the cerebral peduncle presents a safe and relative ‘easy’ surgical route to approach ventrally placed intra-axial midbrain tumors.

Background Endodermal cysts of the oculomotor nerve are rare presentations. Only case reports are available to help guide clinicians with managing this rare entity. Case Description A 3-year-old boy presented with an acute on chronic left oculomotor nerve palsy due to a left interpeduncular cistern cyst found on magnetic resonance imaging. He underwent a left pterional craniotomy and fenestration of the histologically proven endodermal cyst and had initial improvement at the 2-month review. He subsequently developed clinical and radiologic evidence of recurrence and was treated surgically with a refenestration and insertion of a cysto-subarachnoid shunt through a trans-sylvian approach. At 6-month follow-up, there was complete resolution of the oculomotor nerve palsy with interval development of oculomotor synkinesis. Conclusions Magnetic resonance imaging is an essential modality in the follow-up of these patients postoperatively in the setting of unchanged or deteriorated neurology. Fenestration of the cyst is appropriate first-line surgical management; however, a cysto-subarachnoid shunt is a safe consideration in recurrent, symptomatic cysts and provides sustained symptom resolution.

An isolated fourth ventricle (IFV) is characterized by fourth ventricular dilation due to obstruction of its inlet and outlet. A disproportionately large communicating fourth ventricle (DLCFV) is a rare subtype of IFV, characterized by dilation of the fourth ventricle, regardless of the size of the lateral ventricles, with no apparent obstruction of the cerebral aqueduct. To our knowledge, this is the first case series describing endoscopic diagnosis and treatment strategy for DLCFV. We retrospectively reviewed six cases of DLCFV in which endoscopic surgery was performed at our institution and affiliated facilities between June 2013 and March 2017. DLCFV was diagnosed using radiographic imaging and intraoperative endoscopy. We also conducted a PubMed search and included only original studies related to DLCFV treatment written in English in our review of the literature. Endoscopic third ventriculostomy (ETV) was performed in all patients. Additional endoscope-assisted placement of a fourth ventriculoperitoneal (VP) shunt was performed in two patients who could not be managed with ETV alone because of severe adhesion of the interpeduncular cistern due to subarachnoid hemorrhage (SAH). The patients' symptoms and the size of the fourth ventricle improved with surgical treatment, without complications. Endoscopic surgery for DLCFV appears to be a safe and effective treatment. Based on our treatment strategy, ETV is the first-line treatment for DLCFV. Endoscope-assisted placement of the fourth VP shunt can be treatment for severe adhesion of the interpeduncular cistern.

Background and Purpose— Symptomatic vasospasm is an important factor that affects the outcomes of aneurysmal subarachnoid hemorrhage. Subarachnoid blood volume can predict symptomatic vasospasm, and we postulated that the blood clot density would also be an important factor involved in such events. The present study aimed to determine the relationship between the incidence of symptomatic vasospasm and the Hounsfield unit (HU) value of the interpeduncular cistern that reflects the density of hematomas. Methods— Data from 323 patients admitted and treated at a single center between 2008 and 2017 within 24 hours of subarachnoid hemorrhage onset were retrospectively analyzed. Initial HU values of the interpeduncular cistern were measured using CT, then correlations with the incidence of symptomatic vasospasm and HU values as well as other variables were assessed. Results— Symptomatic vasospasm developed in 54 (16.7%) of the 323 patients. The incidence of symptomatic vasospasm was low (1.8%, 2/166) for HU 50 to ≤60, and 45.3%, 29/64 for HU >60). The odds ratio for symptomatic vasospasm was 2.0 (95% CI, 1.6–2.4) per 5 HU increase. Symptomatic vasospasm correlated significantly with intraventricular hemorrhage ( P =0.05) and with intracerebral hematoma ( P =0.046) but even more significantly with the HU value of the interpeduncular cistern ( P Conclusions— The HU value of the interpeduncular cistern on initial CT is an accurate and reliable predictor of symptomatic vasospasm.

There are no literature data on brainstem arachnoid cysts in humans.To describe the clinical case of brainstem (pontomesencephalic) arachnoid cyst and to analyze classification, pathogenesis, differential diagnosis and treatment of this pathology considering literature data and own experience.A 29-year-old patient with pontomesencephalic arachnoid cyst is reported. The disease manifested in childhood with a headache aggravated by bending and pushing. Later, syncope, vegetative-visceral paroxysms, mild oculomotor disturbances, transient paresthesia and numbness of the left half of the face occurred. Headaches became significantly more severe and resulted nausea and vomiting. Magnetic resonance imaging (MRI) revealed a two-chambered arachnoid cyst. A smaller chamber was localized in interpeduncular cistern, a larger one - in brainstem.Differential diagnosis included cystic glioma and Virchow-Robin space enlargement. Fenestration of the cyst wall within interpeduncular cistern was performed via right-sided pterional approach. The diagnosis was verified by histological examination. The follow-up period was 14 months. We observed postoperative cyst reduction confirmed by MR data and regression of all symptoms except for minimal signs of medial longitudinal fasciculus dysfunction.Correct surgical approach for brainstem arachnoid cyst complicated by progressive neurological deterioration is confirmed by postoperative regression of cyst and symptoms.Арахноидальные кисты ствола мозга у человека не описаны.Представить описание клинического случая внутристволовой (понтомезенцефальной) арахноидальной кисты и обсудить вопросы патогенеза, дифференциальной диагностики и лечения данной патологии.Приводится описание клинического случая пациентки 29 лет с арахноидальной кистой, расположенной в толще ствола головного мозга в области перехода среднего мозга в мост. Заболевание проявилось в детстве головной болью, усиливающейся при наклонах и натуживании, затем присоединились обморочные состояния, вегетовисцеральные пароксизмы, легкие глазодвигательные нарушения, преходящие парестезии и онемение левой половины лица; со временем головная боль значительно усилилась, стала сопровождаться тошнотой и рвотой. При магнитно-резонансной томографии (МРТ) выявлена двухкамерная арахноидальная киста с меньшей по размеру камерой в межножковой цистерне и большей — в толще ствола головного мозга.Дифференциальная диагностика проведена с кистозной глиомой и расширением пространств Вирхова—Робина. Операция заключалась в фенестрации стенки кисты, выходившей в межножковую цистерну, и выполнена из правостороннего птерионального доступа. Диагноз верифицирован при гистологическом исследовании биоптата. Катамнез прослежен на протяжении 14 мес. После операции отмечено значительное уменьшение размеров кисты по данным МРТ, регресс всех симптомов, кроме минимальных признаков дисфункции медиального продольного пучка.Правильность выбора хирургической тактики при арахноидальной кисте ствола головного мозга, вызывающей прогредиентное нарастание клинической симптоматики, подтверждается регрессом кисты и симптомов после операции.

BACKGROUND AND PURPOSE: Classic findings of intracranial hypotension on MR imaging, such as brain stem slumping, can be variably present and, at times, subjective, potentially making the diagnosis difficult. We hypothesize that the angle between the cerebral peduncles correlates with the volume of interpeduncular cistern fluid and is decreased in cases of intracranial hypotension. We aimed to investigate its use as an objective assessment for intracranial hypotension. MATERIALS AND METHODS: Brain MRIs of 30 patients with intracranial hypotension and 30 age-matched controls were evaluated by 2 fellowship-trained neuroradiologists for classic findings of intracranial hypotension and the interpeduncular angle. Group analysis was performed with a Student t test, and receiver operating characteristic analysis was used to identify an ideal angle threshold to maximize sensitivity and specificity. Interobserver reliability was assessed for classic findings of intracranial hypotension using the Cohen κ value, and the interpeduncular angle, using the intraclass correlation. RESULTS: The interpeduncular angle had excellent interobserver reliability (intraclass correlation coefficient value = 0.833) and was significantly lower in the intracranial hypotension group compared with the control group (25.3° versus 56.3°; P < .001). There was significant correlation between the interpeduncular angle and the presence of brain stem slumping (P < .001) and in cases with ≥3 classic features of intracranial hypotension (P = .01). With a threshold of 40.5°, sensitivity and specificity were 80% and 96.7%, respectively. CONCLUSIONS: The interpeduncular angle is a sensitive and specific measure of intracranial hypotension and is a reliably reproducible parameter on routine clinical MR imaging.

The study objective is to describe the removal of the pituitary adenoma from the posterior cranial fossa through endoscopic transsphenoidal trans-cavernous approach, when the main surgical corridor was the tumor-intact cavernous sinus. Materials and methods. A 55-year-old male patient with endosupraretrosellar endocrine-inactive pituitary adenoma was admitted to N.N. Burdenko Research Center of Neurosurgery. The patient had earlier undergone two surgeries for pituitary adenoma. Using the endoscopic endonasal transsphenoidal approach, we found that these surgeries resulted in the formation of scar-altered adipose tissue in the sphenoid sinus and partly in the sella turcica; anatomical landmarks indicating the midline and the location of the internal carotid arteries were absent. We formed an access to both retro- and suprasellar portions of the tumor between the sella turcica and cavernous segment of the internal carotid artery (through the cavernous sinus); then we dissected anterior and posterior walls of the sinus and revealed a soft capsule-free pituitary adenoma, which was completely removed by a vacuum aspirator. The skull base defect was repaired using the multilayer technique with autologous tissues. Results. After surgery, neurological status and visual functions did not change. In the postoperative period, we observed no oculomotor disorders, pituitary insufficiency, diabetes insipidus, or nasal liquorrhea. Follow-up computed tomography scans revealed no signs of intracranial complications or obvious residual tumor tissue. Magnetic resonance imaging 4 month postoperatively demonstrated small laterosellar fragments of the tumor in the sella turcica. The patient was further followed up. Conclusion. Cavernous sinus is a natural anatomical corridor providing access to the structures of the posterior cranial fossa and interpeduncular cistern. The main risk (damage to the cavernous segment of the internal carotid artery) can be minimized by using intraoperative dopplerography and visual control of all manipulations.

OBJECTIVEThe expanded endoscopic endonasal approach (EEA) has shown promising results in treatment of midline skull base lesions. Several case reports exist on the utilization of the EEA for treatment of aneurysms. However, a comparison of this approach with the classic transcranial orbitozygomatic approach to the basilar apex (BAX) region is missing.The present study summarizes the results of a series of cadaveric surgical simulations for assessment of the EEA to the BAX region for aneurysm clipping and its comparison with the transcranial orbitozygomatic approach as one of the most common approaches used to treat BAX aneurysms.METHODSFifteen cadaveric specimens underwent bilateral orbitozygomatic craniotomies as well as an EEA (first without a pituitary transposition [PT] and then with a PT) to expose the BAX. The following variables were measured, recorded, and compared between the orbitozygomatic approach and the EEA: 1) number of perforating arteries counted on bilateral posterior cerebral arteries (PCAs); 2) exposure and clipping lengths of the PCAs, superior cerebellar arteries (SCAs), and proximal basilar artery; and 3) surgical area of exposure in the BAX region.RESULTSExcept for the proximal basilar artery exposure and clipping, the orbitozygomatic approach provided statistically significantly greater values for vascular exposure and control in the BAX region (i.e., exposure and clipping of ipsilateral and contralateral SCAs and PCAs). The EEA with PT was significantly better in exposing and clipping bilateral PCAs compared to EEA without a PT, but not in terms of other measured variables. The surgical area of exposure and PCA perforator counts were not significantly different between the 3 approaches. The EEA provided better exposure and control if the BAX was located ≥ 4 mm inferior to the dorsum sellae.CONCLUSIONSFor BAX aneurysms located in the retrosellar area, PT is usually required to obtain improved exposure and control for the bilateral PCAs. However, the transcranial approach is generally superior to both endoscopic approaches for accessing the BAX region. Considering the superior exposure of the proximal basilar artery obtained with the EEA, it could be a viable option when surgical treatment is considered for a low-lying BAX or mid–basilar trunk aneurysms (≥ 4 mm inferior to dorsum sellae).

BACKGROUND AND PURPOSE: Moebius sequence comprises a spectrum of brain congenital malformations predominantly affecting the function of multiple cranial nerves. Reported neuroimaging findings are heterogeneous and based on case reports or small case series. Our goal was to describe the neuroimaging findings of Moebius sequence in a large population of patients scanned with MR imaging. MATERIALS AND METHODS: An observational cross-sectional study was performed to assess brain MR imaging findings in 38 patients with Moebius syndrome studied between 2013 and 2016. RESULTS: Retrospective analysis of MR imaging studies showed flattening of the floor of the fourth ventricle floor secondary to a bilateral absent facial colliculus in 38 patients (100%) and unilateral absence in 1. A hypoplastic pons was found in 23 patients (60.5%). Mesencephalic malformations consisted of tectal beaking in 15 patients (39.5%) and increased anteroposterior midbrain diameter with a shallow interpeduncular cistern in 12 (31.6%). Infratentorial arachnoid cysts were found in 5 patients (13.2%), and cerebellar vermis hypoplasia, in 2 (5.3%). Supratentorial findings included the following: thalamic fusion (26.3%), periventricular nodular heterotopias (26.3%), ventriculomegaly (26.3%), callosal abnormalities (23.7%), and hippocampal malrotations (23.7%). CONCLUSIONS: Findings seen in this large patient cohort agreed with previously published reports. Flattening of the fourth ventricle floor secondary to a bilaterally absent facial colliculus was the most frequent MR imaging finding. The presence of other brain stem and cerebellar malformations as well as supratentorial abnormalities may help explain clinical symptoms and achieve a correct diagnosis.

Endoscopic transorbital approach is a novel development of minimally invasive skull base surgery. Recently, anatomical studies have started to discuss the expanded utilization of endoscopic transorbital route for intracranial intradural lesions. The goal of this cadaveric study is to assess the feasibility of endoscopic transorbital transtentorial approach for exposure of middle incisural space. Anatomical dissections were performed in four human cadaveric heads (8 sides) using 0- and 30-degree endoscopes. A stepwise description of endoscopic transorbital transtentorial approach to middle incisural space and related anatomy was provided. Orbital manipulation following superior eyelid crease incision with lateral canthotomy and cantholysis established space for bone drilling. Extradural stage consisted of extensive drilling of orbital roof of frontal bone, lessor, and greater wings of sphenoid bone. Intradural stage was composed of dissection of sphenoidal compartment of Sylvian fissure, lateral mobilization of mesial temporal lobe, and penetration of tentorium. A cross-shaped incision of tentorium provided direct visualization of crural cistern with anterolateral aspect of cerebral peduncle and upper pons. Interpeduncular cistern, prepontine cistern, and anterior portions of ambient and cerebellopontine cisterns were exposed by 30-degree endoscope. The endoscopic transorbital transtentorial approach can be used as a minimally invasive surgery for exposure of middle incisural space. Extensive drilling of sphenoid wing and lateral mobilization of mesial temporal lobe are the main determinants of successful dissection. Further studies are needed to confirm the clinical feasibility of this novel approach.

Background Shunting procedures have a high failure rate when used to treat pseudotumor cerebri (PTC) patients who have failed medical therapy. This failure is believed to be attributable to the collapsibility of the ventricular system when exposed to increased differential pressure gradients in the cerebral spinal fluid compartments caused by ventriculoperitoneal shunts (VPS). Objective To investigate whether prepontine/interpeduncular cistern shunting may be a reasonable alternative to VPS intervention in PTC patients with history of shunt failure. There have been no large series of cisternal-peritoneal shunt (CPS) patients in the PTC population. Methods A retrospective review of 49 patients with placement of CPS for PTC with 2 failed prior shunting procedures was performed. Shunt survivability was based on shunt patency and resolution of ophthalmologic symptoms and cranial nerve deficits. All patients were followed for a minimum of 3 yr with serial ophthalmologic and neurosurgical evaluations. Results At 3 yr, 44 of the 49 (88.9%) patients had working CPS. Three patients in this group had infections requiring complete shunt removal. Excluding infections, 44 of 46 (95.5%) shunts were functional at 3 yr. There were 3 small, asymptomatic hemorrhages that did not increase patient length of stay, and there were no catastrophic hemorrhages or strokes. There were also no abdominal complications related to shunt placement. Conclusion CPS is a viable alternative to VPS in PTC patients who have failed traditional shunting methods to give these patients a persistent benefit of a working shunt. The procedure provides this solution with low operative and perioperative morbidity.

The hippocampus is susceptible to protein aggregation in neurodegenerative diseases such as Alzheimer’s disease. This protein accumulation is partially attributed to an impaired clearance; however, the removal pathways for fluids and waste products are not fully understood. The aim of this study was therefore to map the clearance pathways from the mouse brain. A mixture of two fluorescently labeled tracers with different molecular weights was infused into the hippocampus. A small subset of mice (n = 3) was sacrificed directly after an infusion period of 10 min to determine dispersion of the tracer due to the infusion, while another group was sacrificed after spreading of the tracers for an additional 80 min (n = 7). Upon sacrifice, mice were frozen and sectioned as a whole by the use of a custom-built automated imaging cryomicrotome. Detailed 3D reconstructions were created to map the tracer spreading. We observed that tracers distributed over the hippocampus and entered adjacent brain structures, such as the cortex and cerebroventricular system. An important clearance pathway was found along the ventral part of the hippocampus and its bordering interpeduncular cistern. From there, tracers left the brain via the subarachnoid spaces in the directions of both the nose and the spinal cord. Although both tracers followed the same route, the small tracer distributed further, implying a major role for diffusion in addition to convection. Taken together, these results reveal an important clearance pathway of solutes from the hippocampus.

Oxygen-induced cerebrospinal fluid (CSF) hyperintensity artifact is inevitable in fluid attenuation inversion recovery (FLAIR) magnetic resonance (MR) images of anesthetized animals. This experimental study aimed to confirm the occurrence of this artifact on low-field magnetic resonance imaging (MRI), and to determine the fraction of inspired oxygen (FiO2) that is safe and does not induce this artifact in canine brain MRI. Six healthy dogs underwent brain FLAIR MR scans under general anesthesia with 21%, 30%, 50%, 70%, and 100% FiO2. The signal intensity (SI) ratio was calculated as the SI of CSF spaces divided by that of normalizing regions. The SI ratios of 21% FiO2 images were significantly different from those of 100% FiO2 images, indicating the presence of artifacts on 100% FiO2 images. The SI ratios of 30% FiO2 images were not significantly different from those of 21% FiO2 images for any of CSF spaces. However, they were significantly different from those of 100% FiO2 images in the cerebral sulci, third ventricle, interpeduncular cistern, mesencephalic aqueduct, and subarachnoid space at the level of the first cervical vertebra (P

Aneurysms of the basilar artery apex are generally at an increased risk of rupture compared with aneurysms in other locations, and the risk of rupture increases with increasing aneurysm size. Therefore, these lesions necessitate treatment to decrease the risk of rupture. The location, size, and directionality of dome projection influence the difficulty of microsurgical treatment. The patient presented with an incidental basilar apex aneurysm identified on workup for headaches. The aneurysm projected superoposteriorly into the interpeduncular cistern. The surgical approach involved a wide exposure of the basilar apex complex and meticulous identification and preservation of P1 perforators during clip applications. It was imperative to visualize all perforators on both sides of the clip prior to application, given the severe morbidity associated with a perforator infarct. The patient tolerated the procedure well and remained neurologically intact after the operation. This video is an exemplary demonstration of basilar apex aneurysm clip application for an incidentally discovered aneurysm. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Background The membrane of Liliequist is one of the best-known inner arachnoid membranes and an essential intraoperative landmark when approaching the interpeduncular cistern but also an obstacle in the growth of lesions in the sellar and parasellar regions. The limits and exact anatomical description of this membrane are still unclear, as it blends into surrounding structures and joins other arachnoid membranes. Methods We performed a systematic narrative review by searching for articles describing the anatomy and the relationship of the membrane of Liliequist with surrounding structures in MEDLINE, Embase and Google Scholar. Included articles were cross-checked for missing references. Both preclinical and clinical studies were included, if they detailed the clinical relevance of the membrane of Liliequist. Results Despite a common definition of the localisation of the membrane of Liliequist, important differences exist with respect to its anatomical borders. The membrane appears to be continuous with the pontomesencephalic and pontomedullary membranes, leading to an arachnoid membrane complex around the brainstem. Furthermore, Liliequist’s membrane most likely continues along the oculomotor nerve sheath in the cavernous sinus, blending into and giving rise to the carotid-oculomotor membrane. Conclusion Further standardized anatomical studies are needed to clarify the relation of the membrane of Liliequist with surrounding structures but also the anatomy of the arachnoid membranes in general. Our study supports this endeavour by identifying the knowledge hiatuses and reviewing the current knowledge base.

A 49-year-old woman presented with an acute intense headache with nausea and vomiting, followed by loss of consciousness. CT scan of head showed diffuse subarachnoid haemorrhage involving the interpeduncular cistern from rupture of a right internal carotid artery aneurysm, which was successfully treated by coil embolisation. On waking in intensive care unit, she reported bilateral central visual loss due to red scotomas. She had reduced visual acuity and unsteady gait. Her visual impairment deteriorated over a few days such that she could only see lights in central visual field and blurred outlines in the peripheral fields. Funduscopy showed vitreous haemorrhage. …

Complete resection of skull base chondrosarcomas offers the potential for a durable, or even lifelong, cure and is best achieved at the first surgery.1,2 When a skull base chondrosarcoma is located at the upper clivus and in the interpeduncular cistern and invading laterally toward the petrous apex and cavernous sinus, the traditional approaches, ie, endonasal endoscopic or middle fossa approaches, are not adequate for the exposure and resection. The transcavernous sinus approach has been utilized to remove tumor from the cavernous sinus and as a corridor to the interpeduncular cistern and upper clivus, originally described for the clipping of basilar apex aneurysms. We present a case of a chondrosarcoma centered in the upper clivus and eroding the right posterior clinoid, analogous to the location of a giant basilar apex aneurysm. Detailed study of the tumor extension, bony invasion, and relationship with neuroanatomy dictated the most effective surgical approach.3,4 Neuronavigation and intraoperative magnetic resonance imaging (MRI) facilitated the gross total resection of the tumor in the Advanced Multimodality Image-Guided Operating (AMIGO) suite. Achieving a gross total tumor removal of this World Health Organization (WHO) grade I chondrosarcoma, adjuvant irradiation can be withheld1 and the patient monitored with serial imaging. The patient did well after the surgery. The patient consented for surgery and the use of photography.

Distal basilar artery aneurysms (DBAs) consist of basilar apex and basilar artery-superior cerebellar artery bifurcation (BA-SCA) aneurysms. The authors aimed to investigate clinical and radiological differences between two locations and to evaluate the 12-month surgical outcome in unruptured DBAs. Fifty-six consecutive patients who underwent surgical treatment (37 basilar apex and 19 BA-SCA aneurysms) between April 2012 and February 2016 were retrospectively evaluated. In patients with a preoperative modified Rankin Scale score (mRS) of more than 1, neurological worsening (NW) was defined as an increase in one or more mRS. In patients without symptoms, NW was defined as mRS ≥2. The mean age of the patient population was 64 ± 9.6 years, and 48 (86%) were female. Mean follow-up period was 2.6 ± 0.94 years. An excellent (mRS 0 to 1) outcome was archived in 31 (55%), 45 (82%), and 48 (87%) patients at 30 days, 6 months, and 12 months, respectively. Clinical and radiological characteristics showed no differences between two locations. One early death (1.8%) and one severe morbidity (1.8%) due to rupture were observed. The postoperative annual rupture rate was 1.4% overall (145 patient-years). After adjustment for age and location, large or giant DBA was related to 30-day and 12-month NW [n = 22 (39%) and n = 6 (11%); p = 0.009 and 0.002, respectively], aneurysm localization in the interpeduncular cistern (LIC) and perforator territory infarction were related to 30-day NW (p = 0.002 and 0.002), and DBA that needed bypass surgery and previously treated recurrent DBA were related to NW at 12 months (p = 0.017 and 0.001). Multivariate analysis showed that LIC was significantly related to perforator territory infarction (p = 0.003). Clinical and radiological characteristics were not different between basilar apex and BA-SCA aneurysms; therefore, they should not be discussed separately. To avoid neurological worsening, results of surgical treatment for unruptured DBAs should be improved.

Deep brain stimulation has become an option for advanced Parkinson's disease treatment since the 1990s, but the first reports are from Benabid's team, a French neurosurgeon, in the 1980s. The subthalamic nucleus (STN), more specifically its dorsolateral portion, is the most commonly stimulated brain area. One of the major aspects for a good surgical result is the accurate location of this target. Therefore, the present article aimed to identify landmarks that facilitate and refine the location of the STN using nuclear magnetic resonance imaging (NMRI) of the skull. In order to achieve this goal, a search for articles was performed using the PubMed and Science Direct online databases, and articles regarding the use of NMRI to target STN were included. The precise location of the dorsolateral portion of the STN is fundamental to achieve the best possible effect on motor symptoms and to minimize side effects. One of the most used location methods is the NMRI, associated or not with tomography or ventriculography. The location strategies can be classified as direct and indirect. Landmarks are among the indirect strategies, and the most important ones (red nucleus, Sukeroku sign, dent internal capsule sign, supramammillary commissure, mammillothalamic tract, and interpeduncular cistern) are described in the present article. The various landmarks can be combined to locate with more accuracy the dorsolateral portion of the STN and the ideal position of the electrodes to achieve the best possible clinical result.

Background Most high-riding distal basilar trunk aneurysms can be surgically approached via the transsylvian route and its orbitozygomatic variant. However, on rare occasions, the basilar bifurcation may be unusually high and an approach above the carotid terminus may be required. Objective In this cadaveric study, we sought to determine the feasibility and exposure limits of the interlenticulostriate approach (ILSA). Methods A standard transsylvian approach was performed in 10 cerebral hemispheres of 5 formalin-fixed, silicone-injected cadaver heads. The interpeduncular cistern was exposed via the opticocarotid window, carotid-oculomotor window, and supracarotid ILSA window. The latter was measured and an aneurysm clip or ventriculostomy stylet was placed as high as possible through each corridor. Using noncontrast 3-D rotational angiography, clip/stylet positions were measured relative to the dorsum sellae. Results ILSA provided a 9.4 × 4.6 mm mean surgical corridor, just enough room for a standard clip applier. This space was limited by the carotid bifurcation inferiorly, the lenticulostriate arteries medially and laterally, and the optic tract superiorly. There was no difference between opticocarotid and carotid-oculomotor windows, in terms of clip position (+8.9 vs +8.6 mm, respectively; P = .78). In contrast, ILSA provided significantly improved superior exposure, compared with either approaches (mean stylet position: +14.3 mm; P = .005). The exposure benefit afforded by ILSA was consistent across all 10 hemispheres, ranging from +2.5 to +8 mm. Conclusion For high-riding distal basilar trunk aneurysms that cannot be reached via the frontotemporal orbitozygomatic approach, ILSA can provide a viable route of access. Vascular neurosurgeons should be familiarized with this approach.

In certain situations, endoscopic third ventriculostomy may be difficult to perform, such as in cases of thickening of the floor of the third ventricle and anatomical variations in the interpeduncular cistern by inflammatory reaction making it difficult to identify the anatomical parameters and perforation of the floor or when the interpeduncular cistern is reduced or occupied by an ectatic basilar artery. Therefore, alternatives to endoscopic fenestrations, diverting and restoring the CSF flow, are extremely useful. This chapter aims to present a study of the anatomical viability of performing a communication between the ventricular system and the longitudinal fissure of the brain, by means of fenestration of the rostral lamina of the corpus callosum, and establish the anatomical parameters for its performance as a surgical procedure by an endoscopic route.

The ventricular access point to the ETV is Kocher’s point, which is located approximately 2 cm lateral to the midline and 2 cm anterior to the coronal suture. The exact site for fenestration is preferably at the midpoint between the mammillary bodies and the infundibular recess. Just below third ventricle floor is located the membrane of Liliequist. The membrane is divided into two portions: the upper one (diencephalic), which is inserted anteriorly to the mammillary bodies, and the inferior one (mesencephalic), which extends to the mesencephalic-pons groove. During ETV to fenestrate mesencephalic portion is mandatory.

Background Intracranial chondromas are extremely rare and represent only 0.2% of all intracranial primary neoplasms. The histologic appearance lacks nuclear atypism and mitoses, and it usually shows low growth potential, although these benign features do not necessarily imply a good prognosis. Case Description A 44-year-old man was referred to our institution with a subarachnoid hemorrhage (SAH). He had a history of SAH 5 years previously that was diagnosed as unknown etiology at another hospital. Head magnetic resonance imaging showed a large tumor located in the prepontine cistern and extending up to the interpeduncular cistern, and the tumor was irregularly enhanced with contrast medium. Retrospective analysis of the original computed tomography of 5 years earlier identified a small contrast enhancing defect behind the dorsum sellae. Tumor removal was planned to prevent repeated SAH and control the apparently growing tumor. An extended transsphenoidal approach was performed. The pituitary gland was dissected from the bottom of the sellar floor and transposed forward to the prechiasmatic cistern with preservation of the pituitary stalk and its blood supply, and subtotal removal of the tumor was achieved. Postoperative diabetes insipidus disappeared within a few days, and the patient was discharged without neurologic or endocrinologic deficits. Histologic examination established the diagnosis as chondroma without a sarcomatous component. Follow-up examination 3 months after surgery showed a re-enlargement of the residual tumor, and gamma knife surgery was performed. Conclusions Intracranial chondroma sometimes manifests as intracranial hemorrhage and grows comparatively rapidly in a short period despite the benign histologic features. A long and careful follow-up period is essential.

The oculomotor nerve supplies the extraocular muscles. It also supplies the ciliary and sphincter pupillae muscles through the ciliary ganglion. The nerve fibers leave the midbrain through the most medial part of the cerebral peduncle and enter the interpeduncular cistern. After the oculomotor nerve emerges from the interpeduncular fossa, it enters the cavernous sinus slightly lateral and anterior to the dorsum sellae. It enters the orbit through the superior orbital fissure, after exiting the cavernous sinus, to innervate the extraocular muscles. Therefore, knowledge of the detailed anatomy and pathway of the oculomotor nerve is critical for the management of lesions located in the middle cranial fossa and the clival, cavernous, and orbital regions. This review describes the microsurgical anatomy of the oculomotor nerve and presents pictures illustrating this nerve and its surrounding connective and neurovascular structures. Clin. Anat. 30:21-31, 2017. © 2016 Wiley Periodicals, Inc.

The cisternal segments of the oculomotor nerve (OMN), which courses through the interpeduncular and oculomotor cisterns (OMC) have not been well delineated on neuroimages. The present study aimed to explore the cisternal segments of the OMN using magnetic resonance (MR) imaging. A total of 92 patients were enrolled in this study. A constructive interference in steady-state sequence was performed in coronal and axial sections. On coronal images, cisternal portions of the OMN were entirely delineated in 97 % on the right and in 98.5 % on the left. Most of the OMCs were of a round shape, with a centrally located OMN, while 9 % were ectatic with the OMN located eccentrically. In 5.3 % of cases, fetal-type posterior communicating arteries (PCoAs), which coursed adjacent to the superior surfaces of the OMNs at the oculomotor triangle (OMT), were observed. On axial images, cisternal portions of the OMN were identified in all cases. The OMN segment passing through the OMT showed medial, central, and lateral courses. The PCoAs and P2 segments of the posterior cerebral artery (PCA) were adjacent to the OMNs in 17 and 19 % of cases, respectively. The OMN most frequently courses in the medial part of the OMT and enters into the OMC. These findings indicate that OMN paresis can be caused by vascular compression at any site of the interpeduncular cistern and OMT.

Subarachnoid hemorrhage (SAH) from rupture of an intracranial arterial aneurysm is a devastating disease affecting young people, with serious lifelong disability or death as a frequent outcome. Large animal models that exhibit all the cardinal clinical features of human SAH are highly warranted. In this pilot study we aimed to develop a non-craniotomy model of SAH in pigs suitable for acute intervention studies. Six Norwegian Landrace pigs received advanced invasive hemodynamic and intracranial pressure (ICP) monitoring. The subarachnoid space, confirmed by a clear cerebrospinal fluid (CSF) tap, was reached by advancing a needle below the ocular bulb through the superior orbital fissure and into the interpeduncular cistern. SAH was induced by injecting 15 mL of autologous arterial blood into the subarachnoid space. Macro- and microanatomical investigations of the pig brain showed a typical blood distribution consistent with human aneurysmal SAH (aSAH) autopsy data. Immediately after SAH induction ICP sharply increased with a concomitant reduction in cerebral perfusion pressure (CPP). ICP returned to near normal values after 30 min, but increased subsequently during the experimental period. Signs of brain edema were confirmed by light microscopy post-mortem. None of the animals died during the experimental period. This new transorbital injection model of SAH in the pig mimics human aSAH and may be suitable for acute intervention studies. However, the model is technically challenging and needs further validation.