Search

A 53-year-old woman was admitted to our hospital for headache secondary to an acute subdural haematoma in the right cerebellar tentorium. She had been diagnosed with systemic lupus erythematosus (S...

Background Intracranial solitary fibrous tumors/hemangiopericytomas (SFTs/HPCs) are rare spindle cell tumors originating from interstitial tissue that are usually benign. Primary malignant intracranial SFTs/HPCs are extremely rare. Here we describe a case of malignant intracranial SFT/HPC. Case presentation A 59-year-old woman presented with a space-occupying lesion in the left cerebellar tentorium. Based on imaging findings, we made a preoperative diagnosis of meningioma. During the operation, we found that the tumor had an abnormally rich blood supply and could not be completely removed. Histologic findings, immunophenotype (positive for cluster of differentiation [CD]34, CD99, signal transducer and activator of transcription 6, and B cell lymphoma 2), and a Ki-67 proliferative index of 20-30% for the primary tumor were typical of malignant intracranial SFT/HPC. The tumors showed high sensitivity to radiotherapy and the residual tumor was significantly reduced after intensity-modulated radiation therapy. The patient has had no neurologic symptoms and no recurrence of the tumor in 2 years of follow-up. Conclusion Intracranial SFTs/HPCs are extremely rare. Radiologic examination before the operation is helpful for making a definite diagnosis and judging tumor grade; STAT6 immunohistochemistry is a sensitive alternative diagnostic method. Adjuvant radiotherapy is effective in cases of incomplete resection, and strict follow-up is essential in order to monitor for possible recurrence.

Background and importance The occipital transtentorial approach is used to address lesions at the posterior incisural space or upper cerebellum. This approach is rarely used, making standardization of the surgical procedure challenging. Here we describe the effectiveness of indocyanine green (ICG) and dye markings before tentorial incision in charting a safe and bloodless surgical trajectory for improved manoeuvrability. Clinical presentation The first case was a 40-year-old man with a residual pineal mass after chemoradiation therapy for pathologically-proven germinoma. Surgical resection was performed via left occipital craniotomy. Incision of the left cerebellar tentorium by a radiofrequency knife was preceded by visualization of the straight sinus and venous lake, which were marked with dye, enabling safe entry into the quadrigeminal cistern. Finally, total-resection of the mature teratoma was achieved. The second case was a 50-year-old man with an enhancing mass at the cerebellar vermis and left hemisphere. Left occipital craniotomy was followed by ICG administration, illuminating the straight sinus and a complex structure of dural venous channels, which were marked with dye. This visualization maximized the tentorial incision by carefully avoiding venous structures and widely exposed the upper cerebellum. Subtotal-resection of the tumor was achieved, with a diagnosis of glioblastoma. Conclusion ICG administration and dye marking are feasible and useful methods for precise identification/visualization of venous structures. They enable maximization as well as safe and appropriate tentorial incision to provide a sufficient surgical corridor for the occipital transtentorial approach.

Patient: Male, 42-year-old Final Diagnosis: Traumatic posterior cerebral artery aneurysm Symptoms: Deterioration of mental status and disorientation Medication: — Clinical Procedure: Parent artery occlusion by endovascular approach Specialty: Neurosurgery Objective: Unusual clinical course Background: Subdural hematoma (SDH) caused by traumatic intracranial aneurysm (TICA) is rare. TICAs are known to rupture easily, resulting in a high morbidity and mortality rate. Therefore, accurate diagnosis and treatment are crucial for preserving life. We describe a case of delayed SDH in the setting of posterior cerebral artery (PCA) aneurysm. Case Report: A 42-year-old man presented with sustained head injury from a traffic accident, and was being followed-up conservatively for traumatic SDH and subarachnoid hemorrhage. Three weeks after the head trauma, the patient developed a sudden deterioration of mental status and disorientation. Computed tomography revealed de novo SDH at the cerebellar tentorium. Computed tomography angiography and magnetic resonance imaging demonstrated TICA in the PCA. The patient was diagnosed with SDH due to a ruptured PCA aneurysm at the quadrigeminal segment. To avoid SDH growth due to re-rupture of the aneurysm, parent artery occlusion was subsequently performed with no complications. The patient was discharged home 2 months after endovascular treatment, with moderate disability. Follow-up angiography 2 years after the operation showed no recanalization, and the patient had returned to work. Conclusions: TICA in the PCA can cause tentorial SDH with or without the presence of subarachnoid hemorrhage. Routine cerebrovascular assessment is crucial for head trauma with hematoma adjacent to the cerebellar tentorium. Parent artery occlusion via an endovascular procedure is an alternative treatment for TICA in the PCA that is less invasive than other approaches.

Background A rare case of a solitary fibrous tumor/hemangiopericytoma (SFT/HPC) expanding the superior and inferior cerebellar tentorium is described. Case description A 28-year-old male presented with convulsions. Magnetic resonance imaging revealed a tumor around the right cerebellar tentorium. The tumor was completely removed after embolization of the feeding arteries, and the pathological diagnosis was World Health Organization grade III SFT/HPC. The patient's postoperative course was uneventful, and there was no recurrence or extracranial metastasis at 1.5 years following the operation. Conclusions It was possible to fully remove the SFT/HPC tumor; however, strict observation of the whole body is needed because of the possibility of recurrence and extracranial metastasis.

In this study, we present a rare clinical case of haemangiopericytoma (HPC) of the supra/infratentorial cerebellar tentorium invading the transverse and straight sinuses and the torcular Herophili in a 31-year-old woman. The patient underwent total microsurgical tumour removal (World Health Organisation [WHO] grade II, International Classification of Diseases [ICD]: 8815/1) and received adjuvant radiation therapy on the site of the resected tumour bed. Despite treatment, HPC metastasised to the thoracic (Th7) and lumbar (L4) spinal regions after 18 months. The metastatic foci were removed, and Th6–Th9 transpedicular stabilisation was performed. The degree of anaplasia of the secondary foci increased to WHO grade III, ICD-8815/3. Cases of intracranial HSC spinal metastasis are rare and poorly understood. Moreover, the close connection between the cerebral venous outflow and paravertebral venous plexus and the absence of the valve system allows the metastatic embolus to remain in the vertebral body. Therefore, sinus wall invasion and metastasis into the sinus lumen is a risk factor for dissemination. Based on our experience, remote metastases can have a higher degree of malignancy, indicating the need for the early diagnosis of metastatic foci.

Objective Dural arteriovenous fistulae of the middle meningeal artery are rare. There are few reports of complications associated with endovascular therapy. This report describes two cases of iatrogenic middle meningeal arteriovenous fistula due to vascular injury sustained during endovascular treatment. Case description Case 1 was that of a 46-year-old woman. She was treated for an incidentally discovered dural arteriovenous fistula of the cerebellar tentorium by transarterial embolization. During the procedure, a middle meningeal arteriovenous fistula occurred because of vessel laceration by the forced advancement of the distal access catheter (DAC). After the intervention, she developed tinnitus. Follow-up angiography revealed a middle meningeal arteriovenous fistula. The fistula was treated by coil embolization of the affected middle meningeal artery. The second case was that of a 56-year-old woman who developed a middle meningeal arteriovenous fistula from the perforation caused by the microguidewire during tumor embolization. The fistula was treated by occluding the proximal segment of the affected artery with coils. Both patients were discharged without neurological complications after the endovascular procedures. Conclusion Endovascular surgeons should be aware of the possibility of middle meningeal arteriovenous fistula as a potential complication of endovascular procedures.

Objective To evaluate the usefulness of a Doppler technology highly sensitive for low-velocity flow in the antenatal imaging of the torcular herophili (TH) in the second trimester of pregnancy. Design Prospective study. Setting Referral Fetal Medicine Unit. Population Non-consecutive series of singleton pregnancies submitted to antenatal neurosonogram between 20 and 28 weeks of gestation. Methods A midsagittal section of the fetal brain was obtained by insonating through the anterior fontanelle, then the MV-Flow™ and LumiFlow™ presets were selected to visualise the TH as the posterior confluence of the superior sagittal sinus and the straight sinus. Main outcome measures Evaluation of the anatomic relationship of the TH with the 'transpalatal line' joining the upper bony palate to the fetal skull. Results A total of 99 pregnant women were recruited, including one fetus with open spina bifida, one with Dandy-Walker malformation (DWM) and two with Blake's pouch cysts. In normal fetuses, the TH appeared to lie on or just below the 'transpalatal line'. In the cases of Blake's pouch cyst, the position of the TH appeared normal if compared with controls, whereas in DWM a supra-elevated position of the TH in respect of the transpalatal line was demonstrated. Finally, in the fetus with Chiari II malformation the TH was identified below the 'transpalatal plane'. Conclusions Prenatal ultrasound visualisation of the TH by means of newly developed Doppler technologies characterised by high sensitivity for low-velocity flow is feasible and allows the indirect evaluation of the insertion of cerebellar tentorium in the second trimester. Tweetable abstract Prenatal imaging of the torcular herophili using a Doppler technology highly sensitive for low-velocity flow.

The trigeminal nerve is often displaced by petroclival meningioma (PCM) compression, making it difficult to locate during PCM surgery. This study investigated whether the deviated position of the trigeminal nerve could be easily predicted using the main tumor feeding artery. We retrospectively examined 32 patients who underwent surgery for primary PCM. The deviation of the trigeminal nerve was classified as either Type 1 (displacement toward the back of the cerebellar tentorium), Type 2 (toward the back of the superior petrosal sinus), Type 3 (toward the back of the petrous apex dura), Type 4 (toward the inferior aspect of the tumor), or Type 5 (toward the surface of the brain stem). The main feeding artery was determined by preoperative angiography. The trigeminal nerve was classified as Type 2 in 60% of cases where the proximal tentorial artery (TA) was the main feeding vessel. The nerve was Type 5 where the distal portion of the TA was the main feeding vessel (60% of the cases). The nerves were Type 3 and Type 4 where the proximal inferior lateral trunk (ILT) (60%) and distal ILT (75%), respectively, were the main feeding vessels. In 66.7% of the cases where the dorsal meningeal artery was the main feeding vessel, the nerve was Type 3. Type 1 classification applied in all cases where the ascending pharyngeal artery was the main feeding artery. The main feeding artery can be used to predict trigeminal nerve transposition during PCM surgery.

Objectives: To describe the outcome of primary meningeal sarcoma (PMS) in a pediatric population. Methods: We conducted a retrospective study on patients harbouring a PMS based on the French registry of paediatric tumours. Questionnaires were sent to all French paediatric oncologists. Data on patient characteristics and treatments were collected. Pathology and imaging were centrally reviewed. Results: Between August 1989 and May 2010, 12 patients from 6 French centres, aged 3 months to 14.5 years (mean: 3.3 years) were treated for a PMS. Mean follow-up was 12 years (range: 3 months to 24 years). Tumour locations were: frontal (3), parieto-occipital (2), parietal (1), temporal (1), occipital (1), thalamic (1), pontocerebellar angle (1), cerebellar tentorium (1), ambient cistern (1). No metastasis was observed. The first-line treatment was surgery in 10 cases, chemotherapy in 2. Resection was total in 6 cases, partial in 6. Central pathology review concluded to: high-grade undifferentiated sarcoma (8), chondrosarcoma (2), fibrosarcoma (1), myxoid desmoplastic tumour (1). Seven tumours were smaller than 5 cm in size. Eleven patients received 2 to 10 courses of chemotherapy (median: 5) but no response was observed. Four out of 6 patients for whom a total resection was performed were still alive at time of study, compared to 2 when only partial resection was possible. Four out of 6 patients who received radiotherapy are still alive, compared to 1 out of 4 patients without radiotherapy. The 5-year Event-Free Survival (EFS) and Overall Survival (OS) rates were 50%. The median EFS in case of total resection was 39 months versus 16 months in case of partial resection. Neither correlation was found between tumour size and location or between age at diagnosis and EFS/OS. Conclusions: We report the first multicentre case series describing clinical, radiological presentation and outcome of PMS in children. In this short series of very rare tumours, age and tumour size did not seem to be prognostic factors. Total resection and radiotherapy seem to be essential. The role of chemotherapy remains unclear.

Background: Tentorial dural arteriovenous fistula (TDAVF) is a rare intracranial vascular shunt. A TDAVF can be supplied by the Artery of Wollschlaeger and Wollschlaeger (AWW). However, a limited number of cases of TDAVF fed by the AWW have been reported to date. Case Description: A 70-year-old woman complaining of the right motor weakness underwent magnetic resonance imaging. A vascular lesion beneath the cerebellar tentorium was incidentally found with chronic infarction of the left corona radiata. Angiographically, the vascular lesion was a TDAVF supplied by the bilateral posterior meningeal arteries. No other apparent feeders were detected. The TDAVF had a shunting point on the inferior surface of the cerebellar tentorium with venous retrograde flow (Borden type III, Cognard type III). To prevent vascular events, endovascular embolization was performed using n-butyl-2-cyanoacrylate. Following embolization of the shunting point, a residual shunt fed by the AWW was identified. The shunt supplied by the AWW was not observed preoperatively. Follow-up angiography performed 1 week later revealed spontaneous disappearance of the residual shunt. The patient was followed-up in our outpatient clinic, and no recurrence of the TDAVF was confirmed postoperatively. Conclusion: Detection of mild feeding from the AWW to a TDAVF can be elusive preoperatively. Following embolization of the main shunting point, residual shunting from the AWW can resolve spontaneously.

Background Accumulation of contrast medium in the subdural space after diagnostic intraarterial and intravenous contrast administrations is a rare observation. The authors report the case of a subdural contrast effusion (SCE) mimicking an acute subdural hematoma (SDH) presenting during embolization of an intracranial dural arteriovenous fistula (DAVF). Clinical history A 52-year-old woman was admitted to our department with a four months history of left-sided numbness of the upper lip, cheek, tongue and forehead. Digital subtraction angiography showed a right tentorial DAVF with a venous ectasia. The DAVF was mainly supplied by the right middle meningeal artery, occipital artery and the artery of Bernasconi-Cassinari and drained into the Galenic venous system. Procedure The patient underwent endovascular treatment with triaxial catheterization of the right occipital artery. Transarterial embolization using PHIL was performed and monitored by control runs made with an intermediate (distal access) catheter. After several injections, increased accumulation of contrast medium along the cerebellar tentorium and the walls of both transverse sinuses was noted. An immediately performed Dyna CT showed extensive contrast medium in the subdural space of the posterior cranial fossa and foramen magnum suspicious for an acute SDH. The catheters were removed, and the procedure was terminated. The patient woke up presenting no new symptoms and had an uneventful postoperative course. A 24-hour follow-up Dyna CT was completely normal suggesting the diagnosis of an asymptomatic SCE. We believe that repeat high pressure contrast injections via a large bore intermediate catheter into the territory of a (even partly) occluded DAVF may have induced leakage of contrast medium into the extravascular subdural space thereby causing a SCE. Summary In conclusion we present the unique case of an asymptomatic SCE, which developed during transarterial embolization of a DAVF. SCE can occur during endovascular therapy and may mimic an acute SDH. Differentiation between the two by computed tomography or Dyna CT and early neurological examination can be crucial for patient management. Disclosures R. Dahl: None. V. Eskesen: None. G. Benndorf: None.

To provide anatomic basis for the retrosigmoid supra-tentorium to infra-tentorium keyhole approach and to explore the feasibility, 60 skulls were observed and measured to demonstrate the position relations among related bony landmarks, 12 cadaveric heads were dissected and measured for localization of the keyhole and the incision through tentorium. For giving the angle and depth for endoscopic approach, 40 adult volunteers were performed head MRI scan and the pictures were measured and analyzed. The surface projection of sigmoid and transverse sinus can be positioned by mastoidale, external occipital protuberance, and anterior end of parietomastoid suture (AEPMS) on body. There is a safe trigone of cerebellar tentorium (STCT) among inner edge of upper curve of sigmoid sinus, entrance of tentorial sinus/vein and midpoint of posterior edge of temporal arcuate eminence. 15 mm superior to the midpoint between asterion and AEPMS can be recognized as the central point of the keyhole. Magnetic resonance imaging pictures show there is potential subarachnoid space for endoscopic approach from the indicated keyhole to pontocerebellar trigone. This study demonstrated endoscopy can arrive at pontocerebellar trigone through the STCT and the keyhole supra-tentorium to infra-tentorium endoscope approach is feasible in anatomy and will contribute to excise lesions involving both supra- and infra-tentorial structures.

We report a case of primary intracranial malignant melanoma (PIMM) with extracranial metastases. The patient was an 82-year-old woman diagnosed with PIMM under the left cerebellar tentorium. We performed a tumor resection followed by gamma knife surgery. An magnetic resonance imaging at 11 months after surgery showed a local intracranial recurrence. At 12 months, vertebral metastasis was suspected, and 2-[fluorine-18]-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) showed multiple extracranial metastases. She died at 13 months after surgery. Although extracranial metastases of PIMM are extremely rare, we should carefully follow up extracranial metastases together with intracranial ones, especially by FDG-PET/CT, even at an early asymptomatic stage.

Background Recently, transposition of the offending vessel has become the gold standard technique in microvascular decompression for trigeminal neuralgia. Teflon felt is the main material used, and the effectiveness of transposing the offending vessel to the cerebellar tentorium using Teflon felt has been widely demonstrated. However, foreign body reaction occurs in some cases causing granulation tissue formation and recurrence of trigeminal neuralgia. We investigated an alternative technique where the offending vessel (superior cerebellar artery) is transposed to the superior petrosal vein without use of Teflon felt for treating trigeminal neuralgia. Methods This study involved 12 patients who underwent surgery using the hanging technique for trigeminal neuralgia in which the superior cerebellar artery was the offending vessel. Surgery was performed using the retrosigmoid approach. The horizontal fissure of the cerebellum was opened, the root entry zone of the trigeminal nerve was accessed via the infratentorial supracerebellar approach, and the superior cerebellar artery was detached and released. The artery was then moved to the tentorium, formed into a loop, hung on the superior petrosal vein, and affixed with fibrin glue. Results Facial pain improved in all cases and sufficient decompression of the trigeminal nerve was confirmed on imaging postoperatively. Conclusion This hanging technique is expected to have low risk of recurrence of trigeminal neuralgia because it does not use foreign materials potentially causing granulation tissue formation and adhesion around the trigeminal nerve. This simple practical technique using existing anatomical structures and no foreign materials appears promising, although long-term follow-up is required.

The main birth traumatic injuries of the skull and brain are described: caput succedaneum, subaponeurotic (subgaleal) hemorrhage, region of periosteal congestion of the skullcap, cephalhematoma, fractures of the skull bones, epidural hemorrhage, injuries of the cerebellar tentorium, injuries of the falx, bridging veins, and compression of the skull and brain. It is the detection of these lesions that is the basis for diagnosing the birth trauma of the skull and brain. The chapter describes in detail the law, first discovered by the author, between the location of the region of periosteal blood congestion (RPC) and the localization of Tentorium cerebelli (TC) laceration. The author explains why lesions of TC occur more often in his left half. A detailed morphological classification of TC injuries is given. The chapter focuses on signs of compression of the brain, which are often not detected.

For brain magnetic resonance (MR) examination, three-dimensional imaging is commonly performed. Radiologists need to know the appropriate imaging angle for viewing. We present six imaging angles for the axial images. Each angle is determined by the reference line. The landmarks on the midsagittal MR image to determine the angle of the reference lines are as follows: the supraorbito-meatal line (the center of the mammillary body and the fastigium of the fourth ventricle), the orbito-meatal (OM) line (the center of the mammillary body and the most posterior point of the cerebellar tentorium), the Talairach anterior commissure (AC)-posterior commissure (PC) line (the superior edge of the AC and the inferior edge of the PC), the Schaltenbrand AC-PC line (the center of the AC and the center of the PC), the subcallosal line (the inferior border of the genu and the inferior border of the splenium of the corpus callosum), Reid’s baseline (the center of the pituitary gland and the most posterior point of the cerebellar tentorium) and the brainstem vertical line (the line perpendicular to the posterior border of the brainstem). The AC-PC line is most commonly used in MR examination. The OM line is most commonly used in computed tomography examination. The supraorbito-meatal line is recommended for avoiding irradiation to the orbit. In cases of multiple sclerosis, the subcallosal line is recommended in the guidelines. For lesions in the orbital cavity, paranasal cavity or skull base, Reid’s baseline is useful. For cases of brainstem lesions, the brainstem vertical line is useful.

Hemangiopericytoma of the cerebellar tentorium with sub and supratentorial growth, Fungal granulomas, Fibrosarcoma of the skull base

We describe a case of atretic cephalocele (AC) characterized by the presence of various cerebral anomalies of different midline structures. In our patient the presence of a parietal AC was associated with an embryonic position of the straight sinus, fenestration of the superior sagittal sinus, an abnormal insertion of the cerebellar tentorium with prominence of the superior cerebellar cistern and a septum pellucidum cyst. These findings, associated with AC, could lead to a worse prognosis with regard to neurodevelopmental milestones. This suggests that even if AC is a benign lesion, a complete evaluation of the brain structures should always be performed in these young patients.

The intracranial space (ICS) is incompletely separated by the cerebral falx and the cerebellar tentorium into three compartments. To simulate brain herniation, defined as part of the brain shifting from one compartment to another, we proposed a simplified model of the supratentorial space (STS) based on computed tomographic (CT) images obtained from 50 subjects. After identifying skull regions, we manually outlined the STS regions on CT slices. Pertinent dimensions of the STS and its openings were measured. The average volumes of the ICS and the STS were 1326 and 1154 mL. The average length, width and height of the STS were 154.7, 136.1, and 90.3 mm. The average length and height of the subfalcine space (SFS) were 85.8 and 52.1 mm, while the average length and width of midbrain were 37.9 and 30.9 mm. Based on these data, we constructed a half sphere STS model with a diameter of 160 mm and a volume of 1072 mL. A 40 mm circle representing the tentorial incisura is removed from the center of its equatorial plane. This model is then divided into two compartments by its intact mid-sagittal plane, which had another 80 mm semicircle removed to simulate the SFS.

Transient bradycardia, hypotension, and asystole arise from activation of the trigemino-vagal reflex by direct stimulation of the trigeminal nerve or branches in the dura mater or cerebellar tentorium. We report two cases of transient asystole during surgery by activation of the trigemino-vagal reflex. In one case, a 63-year-old woman with an unruptured internal carotid artery aneurysm at the origin of the anterior choroidal artery underwent craniotomy. When a clip applied for neck clipping touched the dura mater, transient asystole occurred twice, lasting 4-5 seconds each. After immediate cessation of surgical manipulation, heart contractions recovered spontaneously. The trigemino-vagal reflex may occur in any open craniotomy surgery, and is not rare in clipping operations for supratentorial unruptured aneurysm. However, this reflex recovered without any postoperative complications following prompt cessation of surgical manipulations. (Received July 9, 2012;accepted April 2, 2014)

The authors describe a modified anterior transpetrous approach (ATPA) for the surgical resection of 21 cases of petroclival meningiomas (PCMs). Briefly, a curved periauricular skin incision was used. The cerebellar tentorium and the dura on the petrous apex were coagulated and incised to expose the petrous apex bone fully. The drilling of the petrous apex bone was performed subdurally and began internally from the trigeminal impression, not exceeding 1.5 cm laterally, not exceeding 6 mm from the posterior edge of the petrous ridge, and not exceeding 8 mm in depth from the surface of the petrous bone. The tumors were removed totally in 12 (57.1 %) cases, subtotally in 8 (38.1 %) cases, and partially in 1 (4.8 %) case. The transient neurological deficit includes mild oculomotor nerve palsy in three cases, abducens nerve palsy in six cases, language disorder in three cases, and mild hemiplegia in two cases. Facial numbness became worse postoperatively in six patients, and only two patients improved at 6 months after surgery. No death occurred in this series. The modified ATPA is an efficient treatment alterative for large or giant PCMs located at the medial and superior internal acoustic meatus with relatively low risk of complications.

Sarcoidosis is a systemic granulomatous disease with unknown cause, which very rarely occurs exclusively in the central nervous system. The authors performed biopsy sampling of a mass that developed in the left tentorium cerebelli that appeared to be a malignant tumor. The mass was diagnosed as a sarcoid granuloma, which was confirmed with the onset of antibody reaction product against Propionibacterium acnes. Findings suggesting sarcoidosis to be an immune response to P. acnes infection have recently been reported, and they give insight for diagnosis and treatment of this disease. The authors report the possible first case that was confirmed with P. acnes infection in a meningeal lesion in solitary neurosarcoidosis.

Three patients undergoing surgery for cerebello-pontine angle meningioma suffered transient episodes of asystole. All patients exhibited return to the previous heart rate with cessation of surgical manipulations and administration of anticholinergic agents. These reactions were apparently elicited by activation of the trigeminocardiac reflex (TCR) by direct stimulation of the trigeminal nerve or branches in the dura mater or cerebellar tentorium. Remifentanil was used in all three cases as an anesthetic agent, so may be a cause of the TCR. The possibility of activation of the TCR should be considered during surgical manipulation around the trigeminal nerve or the distribution of the trigeminal nerve branches. Transient bradycardia, hypotension, or asystole can occur regardless of whether there is pressure on the brainstem during posterior fossa meningioma surgery.

This 15-year-old boy with a tentorial cavernous angioma reported occasional headache and scintillation in his left visual field. Magnetic resonance imaging revealed a well-demarcated, homogeneously enhanced tumor originating from the right cerebellar tentorium and extending into both the supratentorial and infratentorial spaces. Although a meningioma was suspected, vertebral artery angiography revealed a thickened meningeal branch originating from the right posterior inferior cerebellar artery and flecked tumor stain with pooling of contrast medium until the late venous phase. A cavernous angioma of the tentorium was suspected based on this finding, and as expected from the radiological findings, profuse bleeding was encountered during tumor removal. The histological diagnosis was a cavernous angioma. A cavernous angioma of the tentorium is extremely rare but should be differentiated from a meningioma preoperatively given that a cavernous angioma of dural origin tends to bleed massively during removal.

✓ The upward odontoid displacement observed in basilar invagination (BI) is generally associated with a horizontal clivus and craniocervical kyphosis, conditions that exert ventral compression at the spinomedullary junction. Ventral brainstem decompression by reduction or elimination of the odontoid invagination is part of the desired treatment. The authors describe a case of BI in an adult, who was effectively treated with the easy and safe reduction of odontoid invagination via cervical traction. Normalization of kyphosis at the craniovertebral junction and the vertical position of both a previously horizontal clivus and the cerebellar tentorium demonstrated that these conditions were not part of the original malformation but instead were caused by a reducible craniovertebral instability.

The paediatric posterior fossa is a complex structure made up of both neural elements and skeletal pieces. The first structures to be formed are the neural elements followed later by bones moulded around the already patterned neural elements. The nervous structures derive from the neural tube at the exact level of the rhombencephalon (also called the hindbrain). This neural tube is segmented into neuromeres called the rhombomeres. These structures form compartments in which cell migration is restricted. Furthermore, these compartments display specific gene expression and if the expression of a gene is forced into an aberrant rhombomere, a severe defect is determined in its own development. The cerebellum, that is one of the major neural components at this level, derives from rhombomere 1. It grows in a rostral to caudal direction like a curtain because its rostral progression is prevented by the cerebellar tentorium. The cerebellum arises as two distinct primordia that unite on the midline thanks to migration of the primordium of this structure. An impairment of this structure will generate a defective fusion at the midline. It is important to note that the different anatomical parts of the cerebellum are not regulated by the same molecular processes leading to a heterogeneity of this organ. Lastly, the bony structures of the posterior fossa derive from the mesoderm. We will review the exact contribution of both the somites and the cephalic mesoderm in such a context.

A 56-year-old man presented with episodic intense facial pain. Trigeminal neuralgia was the presumed diagnosis. MRI revealed vascular compression of the root entry zone (REZ) of the trigeminal nerve (TN) (figure 1, A and B). A dural arteriovenous fistula was detected at the left side of the cerebellar tentorium on digital subtraction angiography (figure 2). A dysplastic venous aneurysm of the draining vein was determined to be the compressive vascular lesion seen on MRI. Trigeminal neuralgia is a common neuropathic disorder characterized by episodes of intense facial pain, most often because of a vascular compression of the REZ of the TN.1,2

A 12-week-old female Wire-haired miniature dachshund presented with non-progressive ataxia and hypermetria. Due to the animal’s clinical history and symptoms, cerebellar malformations were suspected. Computed tomography (CT) and magnetic resonance imaging (MRI) detected bilateral ventriculomegaly, dorsal displacement of the cerebellar tentorium, a defect in the cerebellar tentorium and a large fluid-filled cystic structure that occupied the regions where the cerebellar vermis and occipital lobes are normally located. The abovementioned cystic structure and the defect in the cerebellar tentorium were comparable to those seen in humans with Dandy-Walker syndrome. However, the presence of the cystic structure in the occipital lobe region was unique to the present case. During necropsy, the MRI findings were confirmed, but the etiology of the condition was not determined.

Background The primary aim of surgical treatment for falcotentorial meningiomas is gross total excision. The vital surrounding brain structures make this a complex task. Seeking elements that might facilitate presurgical planning we reviewed our surgical records of falcotentorial meningiomas treated during the past 20 years. Methods Between 1975 and 1996, in the Neurosurgical Unit at the University of Rome, “La Sapienza,” 13 consecutive patients underwent surgery for falcotentorial meningiomas that had been localized on preoperative imaging and confirmed by histology. The surgical approach varied according to the site of the tumor. Results Nine meningiomas were totally removed and 4 subtotally. Three patients (23.0%), all treated early in the series, died after the operation. Ten patients (76.9%) survived: 3 (23.0%) had postoperative neurologic complications necessitating reintervention, and 7 patients (53.8%) had an uneventful postoperative course. Two of the 4 patients who had subtotal resections had regrowth at 1 year that responded to radiosurgery. Conclusions The ideal surgical approach to falcotentorial meningiomas should allow gross total removal and minimum brain retraction while safeguarding the galenic system and other vital neighboring structures. Toward achieving this aim we propose detailed preoperative imaging studies to classify falcotentorial meningiomas according to their site and direction of growth—craniocaudal or anteroposterior—in relation to the cerebellar tentorium.

A 9-year-old Boxer dog was referred to the Veterinary Teaching Hospital of the University of Bern for a history of chronic neck pain and gait problems, which rapidly progressed to a non-ambulatory status. Magnetic resonance imaging (MRI) examination of the head revealed a large intra-axial space-occupying lesion that was divided in two portions interconnected by a thin isthmus at the level of the cerebellar tentorium. Histopathology revealed a biphasic malignant neoplasm composed of neuroepithelial and mesenchymal elements. The former displayed characteristics of conventional anaplastic oligodendroglioma involving brisk mitotic activity and glomeruloid microvascular proliferation on a background of a fibrillary round cells with "honeycomb-like" perinuclear vacuolation. Conversely, the sarcomatous moiety exhibited haphazard fascicles of spindle cells amidst an intricate mesh of pericellular basal lamina and broad bands of collagen. Both tumor cell populations immunoreacted for Olig-2 and – to a lesser extent – GFAP. In addition, the sarcomatous areas focally expressed vimentin, muscular actin, and smooth muscle actin. "Oligosarcoma" - an exquisitely uncommon pattern of oligodendroglial malignancy in humans - has not previously been reported to affect dogs, although oligodendroglioma is a common CNS tumor in this species. Whether canine oligosarcoma shares with its human counterpart not only morphological aspects, but also molecular signatures, clinical behavior and responsiveness to therapy merits further investigation. In humans, oligodendroglial differentiation tends to confer significant clinical advantage with respect to prognosis and adjuvant treatment options. The awareness of such hallmarks and the investigation of their impact on prognosis are crucial for improved therapeutical strategies in dogs.

We report our experience and long-term results in the surgical treatment of 27 tentorial meningiomas （TMs）. These cases were operated on between 1980 to 2000.5 and represented 9.8% of all 275 surgically treated intracranial meningiomas in that period. Of the total 29 TMs （additional 2 non-surgically treated TMs）, 25 were women and 4 were men ranging in age from 26 to 75 years （mean 55.2 years）. According to the site of tumor attachment and the venous sinuses, these 29 TMs were divided into 6 subgroups: central （C; 3）, anterolateral （AL; 3）, posterolateral （PL; 6）, free edge （FE; 6）, anteromedial （AM; 3）, and posteromedial （PM; 8）. Various surgical approaches were selected on the tumor location and extension, however, these are divided into 2 approaches. One is anterior or posterior petrosal approach, selected in AL and FE cases and the other is combined occipital-suboccipital approach, selected in C, PL, AM, and PM cases. In 17 patients, total removal （Simpson Grade 1 : 8, II : 9） was achieved, subtotal removal （SG III） in 4, and partial removal （SG IV） in 6. Four patients had surgical complications. Gamma knife radiosurgery was performed in 4 residual and 3 recurrent meningiomas. In all these 7 meningiomas, tumor sizes have been well controlled. With a mean follow-up of 70 months （2 to 157 months）, recurrences occurred in 5 patients （21.7%）, which were subtotal and partial removal cases. Glasgow Outcome Scale scores were GR in 21 patients （77.8%）, MD in 3 （11.1%）, VS in 1 （3.7%）, and D in 2 （7.4%）.

Objective and importance A rare case of dura-based primary cerebral Hodgkin's disease clinically and radiographically indistinguishable from a meningioma is described. Clinical presentation A 55-year-old immunocompetent woman presented with headaches and ataxia. Magnetic resonance images demonstrated a circumscribed diffusely enhancing mass with a dural tail attached to the cerebellar tentorium. Intervention Operative inspection also suggested a meningioma, but a frozen section of the firm mass revealed an inflammatory lesion. Subsequent pathological analysis demonstrated Hodgkin's disease, nodular sclerosing type. An extensive workup revealed no systemic disease. Conclusion This case illustrates the rare occurrence of primary intracranial Hodgkin's disease and its mimicry of meningioma.

Objective The technical difficulty of using the petrosal approach and the likelihood of encountering venous complications depend on the particular temporal venous anatomy. To reduce such potential risks, neurosurgeons must have adequate knowledge of the variations in the anatomy of the temporal venous drainage system, particularly of the temporal bridging veins. Methods In 20 cadaveric specimens, the temporal bridging veins were examined with the aid of an operating microscope. The anatomic location of their termination and of the tributaries of these bridging veins was noted. Results Forty-four terminations and 109 tributaries of the temporal bridging veins were identified in our specimens. The temporal bridging veins were divided into three groups according to the anatomic location of their terminations: 1) the transverse sinus group (seen in all 20 hemispheres), with drainage into the lateral part of the cerebellar tentorium, to which most of the vein of Labbe belongs; 2) the tentorial group (seen in 50% of the 20 hemispheres), with drainage into the medial part of the tentorium, which is composed mainly of the middle and posterior temporobasal veins; and 3) the petrosal group (seen in 55% of the 20 hemispheres), with entry around the superior petrosal sinus, which may limit mobility of the temporal lobe in the petrosal approach. On the basis of this anatomic information, we propose a new classification of the temporal venous drainage system and discuss the clinical implications of these findings. Conclusion In planning the petrosal approach, great care should be taken not only with the vein of Labbe but also with the petrosal bridging veins. Knowledge of this venous anatomy can reduce venous complications during the lateral cranial base approach.

Presentation of Case A 75-year-old woman was admitted to the hospital because of weakness and a tendency to fall. Eight months earlier, a temporal-artery biopsy, with negative results, had been performed elsewhere because of frequent headaches and an elevated erythrocyte sedimentation rate. Magnetic resonance imaging (MRI) of the brain at that time showed enhancement by gadolinium of the cerebellar tentorium, which was more prominent on the right side, in the posterior middle cranial fossa and posterior fossa, without mass effect or evidence of obstruction. Soon thereafter, esophagogastroduodenoscopic and colonoscopic examinations revealed active gastritis, for which the patient received omeprazole. Two . . .

A 20-year-old woman presented with a 2-day history of headache. She had a congenital grayish-blue pigmented nevus on her left side face, which involved ipsilateral sclera and oral mucosal membrane, diagnosed as nevus of Ota (figure 1, A and B). Neuroradiologic manifestation revealed a lesion in the left cerebellar hemisphere, the etiology of the presenting tumor apoplexy (figure 1, C–F). A left cerebellar hemisphere craniotomy was performed. A well-defined black lesion involved dura mater to the pia mater and was firmly attached to the cerebellar tentorium (figure 2, A and B). Histopathologic examination confirmed a meningeal melanocytoma. Postoperative CT demonstrated total tumor resection.1

BACKGROUND AND PURPOSE: The trochlear nerve is so thin that it is rarely observed with MR imaging. Therefore, we used high-resolution MSDE to reliably visualize the cisternal segments of the trochlear nerve. MATERIALS AND METHODS: Participants were 10 healthy young adults (mean age, 24 years), and 20 trochlear nerves were examined. HR-MRC, BS-MRC, and HR-MSDE were performed. A neuroradiologist judged the visibility of the trochlear nerves as 1 of 4 grades (“Excellent,” “Good,” “Fair,” and “Not”) in each MR imaging sequence. The findings were then statistically analyzed with the χ(2) test. RESULTS: Of all 20 trochlear nerves, 6 with HR-MRC, 13 with BS-MRC, and 18 with HR-MSDE were judged as “Excellent.” CSF flow-related artifacts and vessels in the cistern and cerebellar tentorium in HR-MRC tended to prevent the neuroradiologists from identifying the trochlear nerve. Vessels in the cistern and cerebellar tentorium in BS-MRC also tended to prevent the neuroradiologists from identifying the trochlear nerve. Compared with other sequences, HR-MSDE visualized the trochlear nerve more often. The χ(2) test revealed statistically significant differences among the 3 MR imaging sequences (P < .01). The scan time of HR-MSDE was approximately 1.5–2.2 times longer than that of the other sequences. CONCLUSIONS: HR-MSDE is able to clearly visualize the trochlear nerve and has the same or better ability to delineate the trochlear nerve compared with other MR imaging sequences, though its long scan time does not yet yield practical use.

Introduction The resection of petroclival meningiomas presents great neurosurgical challenges. Although multiple surgical approaches have been developed, the retrosigmoid route tends to be used to address tumors that are predominantly located in the posterior fossa. Our modification of the lateral suboccipital retrosigmoid approach with the placement of a tentorial incision yields good visualization of the supratentorial part of the tumor around the midbrain. Methods We treated four patients, one with primary and three with recurrent petroclival meningioma, by our modified approach. After lateral suboccipital craniotomy, the infratentorial part of the tumor was removed after detaching it from the tentorial surface. The cerebellar tentorium was then carefully incised from the supracerebellar angle, taking care not to damage the superior cerebellar artery and trochlear nerve. Results The operative field surrounding the midbrain was widened by this procedure, and safe dissection of the tumor from the brainstem and other neurovascular structures was performed with direct observation of the interface. Conclusions Our approach is a useful modification of the retrosigmoid approach to petroclival meningiomas. It facilitates the safe resection of the supratentorial part of the tumor in the ambient cistern behind the tentorium.

The surgical anatomy of the temporal bone and the cerebellopontine angle was studied in cadavers, by performing simulated surgery via the extended middle cranial fossa approach. This approach is classified into 3 types according to extension of the drilling area of the temporal bone. In this paper, the surgical anatomy visualized by the EMCF type II and type III is described. In the EMCF type II, mastoidectomy and labyrinthectomy are performed completely through the middle cranial fossa, and in the EMCF type III permitting hearing preservation surgery, sections of the middle cranial fossa dura and the cerebellar tentorium are added to House's middle cranial fossa approach. The comprehension of these anatomical structures is essential for surgeons in performing acoustic neuroma surgery. We believe that this study will serve to expand our knowledge of surgical anatomy, and that as a result the EMCF approach for acoustic neuroma surgery will become more popular.