Tentorial Incisura Research Articles

Removal of the roof of the external auditory meatus in approaching the tentorial notch through a low temporal craniotomy

Improved access to the tentorial notch can be obtained by removal of the roof of the external auditory meatus in association with a low temporal craniotomy. This approach decreases temporal lobe retraction and the risk of venous infarction. This method was perfected in the surgical laboratory on five cadavers and was successfully performed in a patient with a giant aneurysm of the posterior cerebral artery.

Magnetic Resonance Imaging of Kernohan's Notch

Abstract Compression of the cerebral peduncle against the tentorial incisura contralateral to a supratentorial mass, the so-called Kernohan's notch. can be a cause of false localizing motor signs. The authors present a case of Kernohan's notch secondary to a traumatic extradural hematoma. The patient developed an oculomotor palsy and a dense motor deficit ipsilateral to the extra-axial hematoma. Magnetic resonance imaging in the postoperative period clearly showed the midbrain lesion. The motor deficit and 3rd nerve palsy subsequently resolved.

Magnetic resonance imaging of Kernohan??s notch

Compression of the cerebral peduncle against the tentorial incisura contralateral to a supratentorial mass, the so-called Kernohan's notch, can be a cause of false localizing motor signs. The authors present a case of Kernohan's notch secondary to a traumatic extradural hematoma. The patient developed an oculomotor palsy and a dense motor deficit ipsilateral to the extra-axial hematoma. Magnetic resonance imaging in the postoperative period clearly showed the midbrain lesion. The motor deficit and 3rd nerve palsy subsequently resolved.

Intracranial dural arteriovenous malformations: factors predisposing to an aggressive neurological course

The natural history of cranial dural arteriovenous malformations (AVM's) is highly variable. The authors present their clinical experience with 17 dural AVM's in adults, including 10 cases with an aggressive neurological course (strictly defined as hemorrhage or progressive focal neurological deficit other than ophthalmoplegia). Two of these 10 patients died prior to surgical intervention and a third was severely disabled by intracerebral hemorrhage. Six patients underwent surgical resection of their dural AVM, with preparatory embolization in two cases. One patient received embolization and radiation therapy without surgery. Six of the seven cases without an aggressive neurological course were treated conservatively, and the seventh patient underwent embolization of a cavernous sinus dural AVM because of worsening ophthalmoplegia. In order to clarify features associated with aggressive behavior, a comprehensive meta-analysis was performed on 360 additional dural AVM's reported in the literature with sufficiently detailed clinical and angiographic information. The location and angiographic features of 100 aggressive cases were compared to those of 277 benign cases. No location of dural AVM's was immune from aggressive neurological behavior; however, an aggressive neurological course was least often associated with cases involving the transverse-sigmoid sinuses and cavernous sinus and most often associated with cases at the tentorial incisura. Contralateral contribution to arterial supply and rate of shunting (high vs. low flow) did not correlate with aggressive neurological behavior as defined. Leptomeningeal venous drainage, variceal or aneurysmal venous dilations, and galenic drainage correlated significantly (p less than 0.05) with aggressive neurological presentation. The latter three angiographic features often coexisted in the same dural AVM. It is concluded that these features significantly increase the natural risk of dural AVM's, and warrant a more vigilant therapeutic strategy.

Supraorbital-pterional approach to skull base lesions.

A surgical approach to the skull base is described. It allows excellent exposure of the cranial base with minimal brain retraction. Deep lesions can be handled via subfrontal, transsylvian, or subtemporal routes during the same operation. This approach is most suitable for large lesions in the suprasellar, parasellar, and retrosellar areas and for those that extend into the cavernous sinus, along the tentorial notch, or into the orbit. After the single bone flap is replaced, there is little or no functional, anatomical, or cosmetic deficit. Our experience in 16 cases and suggestion for the use of this approach are presented.

Arachnoid cyst of the middle cranial fossa--aplasia of temporal lobe?

In 11 cases of intracranial, temporal arachnoid cysts the etiology, clinical and radiographic findings, surgical treatment, and outcome are reviewed in respect of post-traumatic subdural hematoma. Cysts of the middle cranial fossa are susceptible to trauma, which may cause bleeding either into the cyst or into the subdural space. Signs and symptoms of increasing intracranial pressure (ICP), local neurological deficits, and sometimes epileptic seizures may lead to hospitalization. CT or MRI scans are diagnostic in these cases. In cases of intracranial mass lesion with displacement of the midline structures and increasing ICP, osteoplastic craniotomy is performed and the lateral wall of the cyst is resected down to the tentorial notch by a microsurgical procedure, with opening into the basal cisterns. There were no operative or postoperative complications in 11 consecutive cases. However, one boy required a cystoperitoneal shunt 3 months later as a result of hydrocephalus following subdural hematoma. Asymptomatic arachnoid cysts are discussed with respect to brain function and social behavior.

Radiology of large transincisural masses

A large, potentially resectable mass that crosses the tentorial incisura may present unique problems for the neurosurgeon. Fifteen patients with large trans-incisural extraaxial masses were reviewed. The computed tomography and angiography findings are discussed. The importance of alerting the clinician to the presence of a transincisural mass and accompanying computed tomography and angiography findings are emphasized.

Cerebrospinal fluid and extracellular fluid: their relationship to pressure and duration of canine hydrocephalus.

Fifteen greyhound dogs were made hydrocephalic by the transsphenoidal injection of silicone into the basal cisterns at the level of the tentorial incisura. Six of these animals had ventriculocisternal perfusions 4 weeks later and six at 8 weeks, half at 150 and half at 100 mm H2O. Three 12-week dogs were perfused at 150 mm H2O. Serial sections of brain from the ependyma of the left frontal horn to the overlying pia were counted for 14C inulin and 3H methotrexate uptake. Tissue concentrations of both markers varied indirectly with distance from ependyma and from pia, and varied directly with perfusion pressure. The data indicate that the diffusional pathway between cerebrospinal fluid (CSF) and extracellular fluid (ECF) can be modified by CSF pressure changes, i.e., CSF flows from the ventricles and subarachnoid space into the extracellular space when CSF pressures are raised. Brain uptake of inulin and methotrexate was significantly increased in the dogs made hydrocephalic 4 weeks prior to perfusion, but was less so in the 8-week hydrocephalics. Uptake of the tracers in three 12-week animals was similar to that found previously in normal dogs at elevated pressures. These findings correspond in location and time to the periventricular lucencies that are seen by computed tomography in human subacute hydrocephalus. They are apparently due to pressure-related changes in the volume of the ECF.

Decerebrate rigidity and vegetative signs in the acute midbrain syndrome with special regard to motor activity and intracranial pressure.

Decerebrate rigidity, intracranial pressure and vegetative signs were studied in 25 patients. Advanced statistical techniques were used to analyse the interrelationships between muscle activity (IEMG), blood pressure (ABP), intracranial pressure (ICP), pulse rate (HR), respiratory rate (RR), and central venous pressure (CVP) occurring during paroxysms of decerebration. The pattern of reaction is influenced by compression or stress imposed on the brain stem at the tentorial incisure and is related to the degree of cisternal obstruction. Significant differences in reaction were disclosed between provoked and spontaneous decerebration posturing.

Microsurgical anatomy of the region of the tentorial incisura.

The microsurgical anatomy of the tentorial incisura was evaluated in 25 adult cadavers using X 3 to X 40 magnification. The area surrounding the incisura is divided into the anterior, middle, and posterior incisural spaces. The anterior incisural space is located anterior to the brain stem and extends upward around the optic chiasm to the subcallosal area; the middle incisural space is located lateral to the brain stem and is intimately related to the hippocampal formation in the medial part of the temporal lobe; and the posterior incisural space is located posterior to the midbrain and corresponds to the region of the pineal gland and vein of Galen. The neural, cisternal, ventricular, and vascular relationships of each space were examined. The arterial relationships in the anterior incisural space and the venous relationships in the posterior incisural space are extremely complex, since the anterior incisural space contains all the components of the circle of Willis and the bifurcation of the internal carotid and basilar arteries, and the posterior incisural space contains the convergence of the internal cerebral and basal veins and many of their tributaries on the vein of Galen. The discussion reviews tentorial herniation and operative approaches to the incisura.

Traumatic subarachnoid hemorrhage

One hundred and ninety-seven cases with closed head injury were encountered from April 1980 to December 1982. Computerized tomography (CT) scans of these cases showed traumatic intracranial organic lesions such as epidural hematoma, subdural hematoma, and brain contusion. Among these cases, 23 (11.7%) had only subarachnoid hemorrhage on CT scan, which was performed within several hours of the injury. The five adult patients whose CT scans showed massive subarachnoid hemorrhage in the basal, prepontine, and perimesencephalic cisterns had severe brain-stem damage, and their outcomes were poor. Four adult patients whose CT scans showed moderate subarachnoid hemorrhage in the basal cistern had disturbances of consciousness without brain-stem dysfunction, and their outcomes were fair. Impact sites of injury in the seven of 10 patients with small subarachnoid hemorrhage localized in the ambient and/or quadrigeminal cisterns, were face or forehead. This suggested that subarachnoid hemorrhage was produced by shear strain at the craniocervical junction due to hyperextension of the head or by impact at the tentorial notch. All of these cases recovered, but three of the 10 patients had peripheral oculomotor palsy. The four children had relatively good outcomes compared with the adult cases. The outcomes of the 23 cases as measured 3 months after injury according to the Glasgow Outcome Scale were as follows; good recovery 13, moderate disability 4, severe disability 1, vegetative 1, and dead 4.

Primary choroid plexus papilloma of the cerebellopontine angle

A case of choroid plexus papilloma of the cerebellopontine angle, extending from the upper cervical region to the level of the tentorial notch, in a 50-year-old woman is presented. The differential diagnosis of tumors in the cerebellopontine angle and the role of surgical treatment vs. radiation therapy are discussed. (Neurosurgery 12:334-336, 1983)

Temporal lobectomy for epilepsy: mesial temporal herniation as an operative and prognostic finding.

A Series of 23 patients who underwent unilateral temporal lobectomy for complex partial seizures, with a minimum 1 1/2-year follow-up, is reviewed. The most common pathological finding was mesial temporal sclerosis (52%), and this category represents the best overall outcome in terms of either significant improvement or complete remission of the seizure disorder. Seventy-five percent of the patients with this diagnosis had the operative finding of herniation of mesial temporal structures (specifically the uncus and hippocampus) over the tentorial incisura. This finding was also associated with an excellent result. Computed tomography scans with metrizamide enhancement may reveal preoperatively a unilateral herniated mesial temporal lobe or atrophy of mesial temporal structures, both indicating the diagnosis of mesial temporal sclerosis. Improved identification of patients with subtle structural damage to the mesial temporal lobe in association with EEG foci should increase the success of temporal lobectomy for seizure control.

Operative treatment of lesions in the region of the tentorial notch.

After a description of the topographic anatomy, the different approaches to the tentorial notch and the details of technique are illustrated by a few examples. The pterional approach permits surgical treatment of lesions in the supratentorial region of the anterior and middle third of the tentorial opening. Any approach to the infratentorial region can be enlarged and improved by incising and stitching back the free margin of the tentorium. The medial occipital approach is appropriate for space-occupying lesions situated medially in the ascending portion, that is in the posterior third of the free margin of the tentorium. Infratentorial tumours in the cerebello-pontine angle and in the prepontine region, with extension into the tentorial notch, are best treated through the lateral suboccipital approach. A subfrontal infrachiasmatic procedure is indicated in the case of suprasellar lesions with parasellar extension into the tentorial notch, if the anatomy of the optic chiasm allows it. The location of any particular lesion may call for a combination of different approaches.

Microsurgical anatomy of the pineal region.

Thirty cadaver brains were examined under X 6 to 16 magnification in order to define the microsurgical anatomy of the pineal region, particularly the relationship of the pineal body, posterior cerebral artery, superior cerebellar artery, vein of Galen, basal vein of Rosenthal, internal cerebral vein, straight sinus, bridging vein, the size of the tentorial notch, and the third and the fourth cranial nerves. The infratentorial and supratentorial approaches to the pineal region are compared from the viewpoint of microsurgical anatomy.

BRAIN DISPLACEMENT AT THE TENTORIAL NOTCH IN INTRACRANIAL SPACE-OCCUPMNG LESIONS AT DIFFERENT SITES

Acta Neurologica ScandinavicaVolume 62, Issue s76 p. 71-115 BRAIN DISPLACEMENT AT THE TENTORIAL NOTCH IN INTRACRANIAL SPACE-OCCUPMNG LESIONS AT DIFFERENT SITES First published: May 1980 https://doi.org/10.1111/j.1600-0404.1980.tb07682.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume62, Issues76May 1980Pages 71-115 RelatedInformation

RIHSA cisternography in cerebral tumours.

RIHSA cisternography was abnormal in all of 24 patients with supratentorial tumours. The most common finding was asymmetry caused by ipsilateral obstruction of the sylvian fissure and the subarachnoid space around the convexity. Another frequent finding was partial or total obstruction at the tentorial notch, often in combination with reduced or absent activity along the superior sagittal sinus. These disturbances of CSF flow may explain the pathogenesis of raised CSF pressure with cerebral tumours.

CSF-circulation pathways in experimental hydrocephalus of the rat (author's transl)

Experimental hydrocephalus of the rat was produced by cisternal injection of Kaolin-solution. Intraventricular injection of India ink disclosed obstruction of cerebrospinal fluid pathways at the tentorial incisura in the hydrocephalic rat, while the same injection to the normal rat showed diffuse spreading of the dye over whole subarachnoid space of the brain. The injection of the dye into the cerebral subarachnoid space showed obstruction of the dye at the tentorial incisura in the hydrocephalic rat, while sufficient communication was observed between supratentorial and infratentorial subarachnoid spaces in the normal rat. There were however no remarkable differences between the normal and the abnormal rats about distribution of India ink over the cerebrum under macroscopic and microscopic observations. Obstruction at the tentorial incisura was caused by arachnoid fibrosis and granulation and not by tentorial herniation. Considering experimental findings of paucity of adhesive arachnoiditis over the cerebrum and clinical reports of reversibility of the cerebral subarachnoid space, much effort should be made to promote CSF absorption over the cerebrum, instead of external drainage.

Optic Disc Edema in Raised Intracranial Pressure

The pattern and pathogenesis of nonlocalizing visual disturbances, associated with optic disc edema (ODE). raised cerebrospinal fluid pressure, and intracranial space-taking lesions were investigated experimentally in rhesus monkeys with simulated progressive brain tumor and clinically in patients with benign intracranial hypertension. The visual disturbances occurring in one of both eyes were of three types: recurrent attacks of transient obscuration, permanent blindness, and various types of visual field defects. The studies indicate that the visual disturbances are usually due to two mechanisms. The most common is ischemia of the optic disc secondary to ODE. The other, rarer mechanism probably consists of the space-taking lesion causing downward herniation of the parahippocampal gyrus into the tentorial notch, producing compression of the lateral geniculate body and optic tract.

The medial tentorium and incisura: normal and pathological anatomy.

There are large variations in the length and breadth of the tentorial incisura, its relationship to the brainstem, and in the exact course and position of the free tentorial margins. On contrast-enhanced CT scans, the obliquely sectioned posterolateral tentorial leaves of the tentorial notch can usually be delineated easily. Lesions intrinsic to the tentorial hiatus are discussed and the CT features of remote mass effects causing transtentorial herniation described.