Tentorial Research Articles

Expanding the Horizon of the Suboccipital Retrosigmoid Approach to the Middle Incisural Space by Cutting the Tentorium Cerebelli: Anatomic Study and Illustration of 2 Cases

Complex skull base approaches are often used to treat lesions within the middle incisural space; yet the well-known retrosigmoid route may provide an effective avenue to this difficult-to-reach region. The purpose of this study was to quantify the exposure advantages on the middle incisural space provided by cutting of the tentorium cerebelli via a standard suboccipital retrosigmoid approach (i.e., via the cerebellopontine cistern route). Also, 2 illustrative cases are presented. A suboccipital retrosigmoid approach to the middle incisural space was performed bilaterally in 3 specimens in the semisitting position. A quantitative analysis of the brainstem surface exposed above the origin of the trigeminal nerve was performed before and after tentorial incision. Tentorial cutting significantly improved the exposure of the middle incisural space cisternal structures such as the oculomotor and trochlear nerves and the superior cerebellar and posterior cerebral arteries. The mean brainstem surface exposed more than doubled (2.13-fold increase) after tentorial incision with an average increase from 73.18 mm(2) to 155.76 mm(2). When the endoscope was used, it was possible to follow the entire course of the cisternal, infratentorial trochlear nerve segment during theopening of the tentorial free edge, facilitating its preservation. In the illustrative cases, 2 cerebellopontine angle meningiomas with supratentorial and infratentorial extension were removed without any postoperative complication. Tentorial incision may be useful to extend the rostral exposure of the middle incisural space via a simple retrosigmoid approach, avoiding the need for more complex skull base routes.

Basal vein in the posterior incisural space: An anatomical comparison based on autopsy, digital subtraction angiography and computed tomographic venography.

During surgical procedures, the basal vein in the posterior incisural space is susceptible to obstruction. In such circumstances, venous infarction can occur along with venous damage. The aim of this study was to correlate the microanatomy of the basal vein in the posterior incisural space with the digital subtraction angiography (DSA) and computed tomographic venography (CTV). Twenty cadavers and 42 patients were examined in this study. The head of each cadaver was injected with blue-colored gelatin via the internal jugular veins. Venograms for each patient were obtained from the venous phases of DSA or CTV. Compared to the cadavers, in the patients, DSA and CTV revealed 90% and 95% of the basal vein, respectively. According to difference of entrance, three types of basal veins were identified. No statistical difference of typing was found among the cadavers, DSA images and CTV images. On three sides of the cadavers and one side of the CTV images, the basal vein entered the straight sinus through the meningeal vein in the tentorium cerebelli. Preoperative DSA and CTV are useful in the design of individualized surgical approaches and the preservation of the basal vein in the posterior incisural space.

Correlations between Pathological Changes of the Skull Roof during Childbirth and Localization of Hemorrhages in the Tentorium Cerebelli in Newborns

Background: At birth in cephalic presentation in fetuses formed a region on the skull roof – area of the periosteal blood stagnation (APS) that persists in newborns. In newborns with minimal birth trauma, in the Tentorium Cerebelli (TC) formed intradural hemorrhages, which do not lead to death. The relationship between these pathological changes has not been studied. The present study aims to examine it. Method and findings: In a group of 53 neonates and intrapartum dead fetuses it was investigated the correlation between the location of the APS on the skull roof and localization of hemorrhages in TC, consisting of two halves. Two patterns are revealed. First, at a central location in the APS 83.3% of cases there are bilateral uniform hemorrhage in TC, and to an asymmetric, corresponding asynclitic insertion head, - unilateral hemorrhage or prevailing on one side (84%; P <0.01, Q = 0.86). Secondly, the unilateral hemorrhage (or hemorrhage, which is larger in the bilateral hemorrhage) in the TC is predominantly (95.2%) on the side opposite the direction of movement of APS, and more frequently in the left half of the vehicle. Conclusion: The results of the study showed that the emplacement of the hemorrhage in TC of the neonates and fetuses born in cephalic presentation depends on the location of the APS.

En-Plaque Central Nervous System Tuberculoma - An Uncommon Entity: Clinico-Radiological Profile in a Cohort from a Tertiary Referral Centre.

Case reports pertaining to Magnetic Resonance Imaging (MRI) diagnosis of en-plaque tuberculoma are limited. To the best of our knowledge, descriptions about en-plaque tuberculoma are limited to few isolated case reports. This paper comprehensively depicts the clinical and radiological features in such patients and may serve not to miss this uncommon manifestation of a common central nervous system infection. A descriptive documentation of the patient cohort with a detailed history and neurological examination were carried out in all the patients. All underwent MRI Brain which revealed en-plaque tuberculoma. Relevant investigations including Cerebrospinal Fluid (CSF) were done in all patients. CSF Polymerase Chain Reaction (PCR) was done in all. Eight adult patients (two women and six men) with MRI showing en-plaque CNS tuberculoma were seen during a period of five years. None had suffered from TB in the past nor had history of contact with tuberculosis. All patients demonstrated extra axial dural based lesions and none had cerebral ooedema, parenchymal lesions, mass effect or midline shift. The lesions were located in bilateral corresponding regions in two patients and the rest six had unilateral lesions. Seven patients had lesions located in the supratentorial compartment; one had lesion extending to the infratentorium along the tentorium cerebelli. Various patterns of enhancement were noted in our patients: thin peripheral (n=3), homogenous (n=3), varied enhancement (n=1) and open ring enhancement (n=1). CSF Polymerase Chain Reaction (PCR) was tested positive for tuberculosis in all of our patients. While MRI provides an understanding of the topography of the lesion, PCR helped in establishing the diagnosis of tuberculosis in our patients. Awareness about en-plaque tuberculomas can heighten the index of suspicion and can thus prevent aggressive surgical resections and thereby reduce mortality and morbidity.

Embryological Consideration of Dural Arteriovenous Fistulas.

The topographical distribution of dural arteriovenous fistulas (DAVFs) was analyzed based on the embryological anatomy of the dural membrane. Sixty-six consecutive cases of intracranial and spinal DAVFs were analyzed based on the angiography, and each shunt point was identified according to the embryological bony structures. The area of dural membranes was categorized into three different groups: a ventral group located on the endochondral bone (VE group), a dorsal group located on the membranous bone (DM group) and a falcotentorial group (FT group) located in the falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragm sellae. The FT group was designated when the dural membrane was formed only with the dura propria (meningeal layer of the dura mater) and not from the endosteal dura. Cavernous sinus, sigmoid sinus, and anterior condylar confluence was categorized to VE group, which had a female predominance, more benign clinical presentations, and a lower rate of cortical and spinal venous reflux. Transverse sinus, confluence, and superior sagittal sinus belonged to the DM group. Olfactory groove, falx, tent of the cerebellum, and nerve sleeve of spinal cord were categorized to the FT group, which presented later in life and which had a male predominance, more aggressive clinical presentations, and significant cortical and spinal venous reflux. The DAVFs was associated with the layers of the dural membrane characterized by the two different embryological bony structures. The FT group was formed only with the dura propria as an independent risk factor for aggressive clinical course and hemorrhage of DAVFs.

BMET-33ENDOSCOPIC ENDONASAL TRANSPHENOIDAL RESECTION OF A MANTLE CELL LYMPHOMA TO THE SELLA TURCICA

The authors present a case of a 71 year old female with a past medical history significant for mantle cell lymphoma isolated to the peritoneal cavity treated approximately 10 years prior. The patient was deemed to be in remission, but presented to her primary care physician with symptoms of progressive deterioration of her visual fields. An MRI of the brain revealed a contrast enhancing sellar lesion which extended posteriorly to the tentorium cerebelli on the left side. The lesion was noted to cause optic chiasm compression as well as invasion within the cavernous sinus. The patient underwent a successful optic chiasm decompression via an endoscopic endonasal transphenoidal resection of the lesion. Post-operatively, the patient was noted to have a marked improvement in her visual fields. The final pathology revealed mantle cell lymphoma within the sella turcica lesion. The patient received systemic and intra-thecal chemotherapy with exceptional results. Follow-up MRI of the brain revealed interval resolution of the lesion. To the authors' knowledge this is the first reported case of mantle cell lymphoma within the sella turcica.

Intracranial Solitary Fibrous Tumor: A Mimicker of Meningioma.

In September 2009, a 56-year old woman presented to our hospital with meningitis-like complaints. A CT scan demonstrated a small intracranial lesion in the posterior fossa. MRI, performed for further evaluation for this lesion, showed a broad dural-based implantation on the lower surface of the tentorium cerebelli, and a marked enhancement after administration of intravenous contrast (arrow in Fig. A). The diagnosis of a small tentorial meningioma was made. A control CT scan six months later showed no volume increase, after which she was lost to follow up. In October 2011, a new CT scan performed in the context of a minor head trauma, showed a significant volume-increase of this lesion. A new MRI scan was performed which confirmed this. The scan also demonstrated the development of a slight mass-effect on the left cerebellar hemisphere together with minor tumor invasion of the cerebellum and minimal surrounding edema. The tumor showed a heterogeneous aspect on T2 weighted imaging with some small cystic foci (Fig. B). After administration of Gadolinium, a heterogeneous enhancement was present (Fig. C). The preferred diagnosis remained that of a meningioma. Since the tumor appeared to be progressive, surgery was performed with complete resection. Pathological examination of the specimen revealed the lesion to be a meningeal solitary fibrous tumor with malignant features.

Pediatric proximal anterior cerebral artery aneurysm: A case report

Intracranial aneurysms are extremely uncommon in children (≤ 18 years old) and their incidence increases with age. Their epidemiology is poorly understood and certain features like location, morphology and presentation make them unique in comparison to adults. The internal carotid artery bifurcation is the most frequent site for aneurysm in this age group. We report a case of an 8-year-old boy with history of sudden unconsciousness followed by generalized tonic clonic seizures. The computerized tomography scan revealed subarachnoid hemorrhage with blood seen in the left Sylvian fissure, along tentorium cerebelli and posterior falx. There was focal intracerebral hematoma in the left temporal lobe abutting the Sylvian fissure and blood could also be seen in the fourth, third and both lateral ventricles with mild ventriculomegaly. The digital subtraction angiography revealed a large intracranial aneurysm arising from the left proximal anterior cerebral artery just distal to left internal carotid artery bifurcation. The aneurysm was clipped using standard microsurgical techniques. The child did well postoperatively. Intracranial aneurysms are rare in childhood and proximal artery anterior cerebral artery aneurysms are amongst the rarer sites. This report highlights one such rare case.

Craniocerebral Injuries and the Glasgow Coma Scale Score in the Patients under the Influence of Alcohol Admitted to Hospital Emergency Department

Introduction. Alcohol abuse constitutes a significant social and health problem in Poland. Consumption of even a small amount of alcohol causes an increase in the probability of the injury.Aim. The objective of the thesis was to determine the relationship between the scoring in the Glasgow Coma Scale and head injuries in the patients under the influence of alcohol admitted to the Hospital Emergency Department in an urgent mode.Material and Methods. On the basis of the retrospective analysis the group of 210 intoxicated patients of the Hospital Emergency Department of the University Hospital in Cracow (167 men and 43 women) who sustained head injuries during the period from 1st May 2011 to 1st May 2012 was examined. The data included in the medical documentation, such as: age, gender, result of the scoring in the Glasgow Coma Scale, blood alcohol level, sustained head injuries on the basis of the CT examination and selected co-existing post-traumatic disorders were taken into consideration.Results. Among the patients with high blood alcohol level there were people with both high and low results in the Glasgow Coma Scale. The patients with fractures of the facial bones and skull base, epidural haematoma, pericerebral haematoma, subdural haematoma, intracerebral haematoma, subarachnoid haematoma, cerebral edema, displacement of the ventricular system and blood in the location of the cerebellar tentorium had the lower scoring in the Glasgow Coma Scale than other patients. The lowest score in the Glasgow Coma Scale had the patients who fell from height, the highest one — patients after a suicide attempt.Conclusions. Blood alcohol level did not have an influence on the scoring in the Glasgow Coma Scale. There is a relationship between the scoring in the Glasgow Coma Scale and head injuries. The GCS score depended on the symptoms that co-exist with the head injuries. The mechanism (cause) of sustained head injury determined the score in the Glasgow Coma Scale. (JNNN 2015;4(2):56–61)

The technical report of three-dimension visualized image-guided stereotactic biopsy for lesions in pineal region and brain stem

Objective To investigate the methodology, technical essential and significance of three-dimension visualized image-guided stereotactic biopsy(SB) for lesions in pineal region and brain stem. Methods A total of 88 cases of lesions in pineal region and brain stem underwent image-guided SB in our department were retrospectively studied. Frame-based and CAS-2 type frameless SBs were performed in 57 and 31 cases respectively. Pre-biopsy three-dimension visualized image reconstruction was performed by SB planning software and the structure related to possible trajectory in each image slice was confirmed. The most suitable trajectory was selected accordingly. For lesions in pineal region, anterior-frontal trans-tentorium cerebella hiatus trajectory for avoiding tentorial margin was used. For lesions in mesencephalon, posterior-frontal trans-lateral ventrical- thalamus trajectory via the vertical axis of brain stem was used. For pontal lesions , supra-occipital trans- pedunculus cerebellaris medius trajectory was used. Results Histological diagnosis was established in all 88 cases, which gave a high diagnostic yield (100%). Fifty-six lesions (64%) located in brain stem (middle brain and pons) and 32 (36%) in pineal region. In 56 brain stem lesions, there were 38 cases (68%) of glioma, 3(5%) lymphoma, 2(4%) neurodegenerative disease, 6(11%) multiple sclerosis and tumefactive demyelinating lesion, 2(4%) non-specific inflammation, 2(4%)brain infarct, 2(4%) brain metastases, and 1 (2%) radiation necrosis. For lesions in pineal region, there were 18 cases (56%) of germ cell tumor, 4(13%)glioma, 9 (28%) pineal cell tumor, and 1(3%) Wernicke encephalopathy. One case(1 %)died of biopsy-related hemorrhage. The neurological deficits became severe because of hemorrhage in 5 cases, the medical treatment was adopted in 3 cases(3%)and drainage in 2 (2%). Conclusions Stereotactic biopsy for lesions in pineal region and brain stem was a safe and effective procedure that could help for the selection of clinical management and provide important prognostic information. Three-dimension visualized image-guided technique could realize virtually individual visualized intuitionistic view of biopsy trajectory. It could remarkably improve the safety and decrease the operative complications. Key words: Stereotaxic techniques; Biopsy; Brain stem; Pineal region

Frontal Lobe Meningioma Masquerading as Depressive Disorder

Meningiomas are a diverse set of tumors thought to arise from the arachnoid cap cells, which reside in the arachnoid layer covering the surface of the brain [1]. Meningiomas account for approximately 25% of all primary intracranial neoplasms; most of them are benign and their incidence increases with age [2]. These tumors can arise anywhere, most commonly within the skull and at sites of dural reflection (falx cerebri, tentorium cerebelli, venous sinuses) [3]. Meningiomas are extremely slowed growing and often asymptomatic. Small tumors (e.g., <2.0 cm) are usually incidental findings at autopsy without having caused symptoms. Larger tumors can cause symptoms depending on the size and location. The frontal lobes of the brain are notoriously “silent”: Benign tumors such as meningiomas that compress the frontal lobes from the outside may not produce any symptoms other than progressive change of personality and intellect until they are large. Patients with such tumors are often referred first to psychiatrists, and the correct diagnosis may emerge only when the tumor has grown large and has begun to displace the brain [4].

Feasibility and safety of prophylactic tentorium cerebelli hiatus incision in surgery of glioma located in lateral fissure area.

To discuss the feasibility and safety of prophylactic tentorium cerebelli hiatus incision in surgery of glioma located in lateral fissure area. There were 80 patients with glioma located in lateral fissure area who received treatment from May 2012 to May 2015, divided into two groups, the research group (n=40) and control group (n=40), and then statistical analysis was carried out. Difference in total resection rate and subtotal resection rate of glioma between patients of the research group and those of the control group was not significant (P>0.05); intracranial pressure of patients in the research group was significantly lower than that of control group (P<0.05), their hospital stay was significantly shorter than that of the control group (P<0.05), times of using mannitol were significantly fewer than control group (P<0.05), but the differences of acute renal function damage and second surgery occurrence rate between patients of the two groups were not significant (P>0.05). Prophylactic tentorium cerebelli hiatus incision in surgery of glioma located in lateral fissure area can effectively reduce patients’ intracranial pressure, shorten patients’ hospital stay and reduce patients’ times of using mannitol without increasing the rate of patients’ acute renal function damage and second surgery.

Falx Cerebelli Meningioma: Technical Note

Abstract The falx cerebelli is a small sickle-shaped fold of dura mater below the tentorium cerebelli, which projects forward into the posterior cerebellar notch. We report a rare case of 28 year female presented with the history of headache of six months duration off and it increased in severity and frequency over last 15 days. Imaging findings were suggestive of meningiona arising from the falx cerebelli. The lesion could be excised totally and safely.

Lateral suboccipital retrosigmoid approach with tentorial incision for petroclival meningiomas: technical note.

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.

Recovery of the corticospinal tracts injured by subfalcine herniation: a diffusion tensor tractography study.

Recovery of the corticospinal tracts injured by subfalcine herniation: a diffusion tensor tractography study.

A Simple Geometric Model for Simulating Brain Herniation Using CT Craniometry

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 1154mL. The average length, width and height of the STS were 154.7, 136.1, and 90.3mm. The average length and height of the subfalcine space (SFS) were 85.8 and 52.1mm, while the average length and width of midbrain were 37.9 and 30.9mm.Based on these data, we constructed a half sphere STS model with a diameter of 160mm and a volume of 1072mL. A 40mm 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 80mm semicircle removed to simulate the SFS.

未破裂脳動脈瘤クリッピング術中に三叉迷走神経反射による心停止をきたした2例

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)

J0250102 回転性脳損傷に関わる頭蓋内構造因子の検討([J025-01]傷害防止工学セッション(1),バイオエンジニアリング部門)

Diffused Axonal Injury is a type of head injury which occurs frequently in traffic accidents. It is said that it is caused by rotational head movement, and elucidation of the mechanism is necessary. There are three factors affecting the occurrence of DAI based on the intracranial structure; A complicated brain and skull structure, relative motion of the brain and skull with cerebrospinal fluid present?, and the restraint of the brain motion due to cerebral flax and tentorium cerebelli. Although various studies are done based on these three factors, it is difficult to reproduce in solid-model and simulation model, and while the influence of three factors in computational dynamics has been unknown, the simplification of the model is performed in the simulation. In this study, constructed the head neck solid-models which the intracranial structure factors differ, and considered the influence of an intracranial structure factors. The experiment which imitated the collision from the side was conducted on three sorts of the head neck solid-models, and brain depths distortion was measured. It turned out that the experimental result of three sorts of head neck substance models is compared, and it has influence with relative motion important for brain depths distortion between a brain slot and a brain-skull.

A new method for piercing the tentorium cerebelli for implanting fragile electrodes into the brain stem in the rhesus monkey (Macaca mulatta)

Recent developments in neuron recording techniques include the invention of some fragile electrodes. The fragility of these electrodes impedes their successful use in deep brain recordings because it is difficult to penetrate the electrodes through the dura mater, especially the tentorium cerebelli (TC) enclosing the cerebellum and brain stem. This paper reports a new method to pierce the TC for inserting fragile electrodes into the inferior colliculus of rhesus monkeys. Briefly, a unique tool kit, consisting of needles with sharp tips, a guide tube and an "impactor," was used in a multistep protocol to pierce the TC. The impactor provided a brief force that quickly thrusts the needles through the meninges without causing significant damage to the brain tissue under the TC. Using this novel approach, tetrodes were successfully implanted into the inferior colliculus of a rhesus monkey and neuronal discharge signals were recorded. This method, which is simple, convenient and economical, allows neurophysiologists to study the electrophysiological characteristics of deep brain structures under the TC with advanced, albeit fragile, electrodes.

Microanatomical study of the endoscopy-assisted extreme lateral supracerebellar infratentorial keyhole approach to the dorsolateral mesencephalon region

Objective To explore the microanatomy technique of the endoscopy-assisted extreme lateral supracerebellar infratentorial keyhole approach and clinical significance.Methods The extreme lateral supracerebellar infratentorial keyhole approach was imitated in 10 vascular perfusion adult cadaveric heads fixed in formalin,the dorsolateral mesencephalon region was dissected and observed by microscopy and neuroendoscopy from December 2012 to March 2013.Results The extreme lateral supracerebellar infratentorial keyhole approach could be fully exposed the ambient cisterns,the posteromedial tentorial incisura,the dorsolateral mesencephalon region,the trochlear nerve,the root of the trigeminal nerve,the superior cerebellar artery,the posterior cerebral artery and other important anatomical structures.The temporal lobe and parahippocampal gyrus could be exposed when the tentorial was incised.The application of neuroendoscopy could clearly reveal the trigeminal nerve and surrounding structures.Conclusion The extreme lateral supracerebellar infratentorial keyhole approach is suitable for the surgical resection in dorsolateral mesencephalon region.The application of neuroendoscopy can make up for the lack of the trigeminal nerve observed under microscopy and expand the operative field. Key words: Extreme lateral supracerebellar infratentorial approach ; Keyhole approach ; Neuroendoscopy ; Mesencephalon; Microanatomy