Brainstem Retraction Research Articles

Endoscopic Endonasal Approaches for Anterior Skull Base Meningiomas.

Anterior skull base meningiomas are a diverse group of tumors that involve different locations. The role of the expanded endoscopic transnasal approach in the management of anterior cranial fossa meningiomas has significantly changed over the past 2 decades. Patient selection is paramount to benefit from the advantages of endoscopic transnasal surgery such as direct access to ventral skull base lesions avoiding brain and brainstem retraction, early de-vascularization, removal of bone infiltrated by tumor, near-field magnification, better surgical field illumination, and minimal manipulation of neurovascular structures. Here we discuss some of the main limitations and advantages of the endoscopic transnasal approach related to patient selection, including nuances of their management, discussing preoperative imaging and planning, the surgical approach, and future perspectives in the treatment of these tumors.

Apport de l’endoscopie pour la décompression microvasculaire dans l’angle ponto-cérébelleux : à propos de 27 cas

Microvascular decompression is an important procedure for the management of microvascular compression syndromes in the cerebellopontine angle (CPA) like trigeminal neuralgia or hemifacial spasm. The ability to identify the offending vessel is the key to success. Can the endoscope help surgeons to identify and understand the responsible conflict in order to treat them? Our series concerns 27 consecutive patients who underwent microvascular decompression systematically using an endoscope with an angulation of 30° at the beginning and the end of the intervention. The decompression procedure was done under microscope. Endoscopic exploration was successful for all patients. Endoscopy improved visualization of the cranial nerves and allowed to see and understand the neurovascular conflicts, which were not able to be observed using the microscope alone for two of the 27 patients. The endoscope is a useful adjunct to microscopic exploration of the cranial nerves in the CPA avoiding significant cerebellar or brainstem retraction.

Surgery of Craniocervical Meningiomas

Objective: To study the different surgical approaches to craniocervical meningiomas in different locations in the area of the foramen magnum, whether anterior, posterior, antrolateral or posterolateral Methods: Twenty six patients with craniocervical meningiomas were operated upon during the period from 2000 to 2009 using the standard posterior approach for posterior lesions (14 cases), extreme lateral approach without drilling of the occipital condyle in the antrolateral and posterolateral lesions(6 cases) and transcondylar approach for anterior lesions (6 cases). Results: This study included 16 females and 10 males, the patients’ age ranged from 23 to 64 years with a mean of 51.8 years. Tumor size ranged from2 to 6.4 in its maximum diameter. Tumor location was posterior in 14 patients, lateral in 6 patients and anterior in 6 patients. Total tumor resection was done in 23 (88.4%) patients and subtotal in 3 (11.6%) patients. Postoperative complications included transient lower cranial nerves affection, transient hemiparesis. There was no mortality in this study. The follow up period ranged from 6 months to 4.8 years. Conclusion: Surgical approach to craniocervical meningioma has to be tailored according to the location of the tumor. Posterior tumors are safely totally removed through the slandered suboccipital approach. Posterolateral and antrolateral tumors are easily removed via the postero lateral retrocondylar approach without drilling of the occipital condyle benefiting from the working space given by lateral displacement of the brain stem. Anteriorly located tumors are better approached through the extreme lateral transcondylar approach to avoid brain stem retraction. Key words: Foramen magnum, meningioma, occipital condyle, suboccipital approach.

Adjunctive use of endoscopy during posterior fossa surgery to treat cranial neuropathies.

The objective of this study was to determine the utility and safety of rigid endoscopy as an adjunct during posterior fossa surgery to treat cranial neuropathies. A suboccipital craniotomy was performed for 19 patients with non-neoplastic processes involving the Vth, VIIth, and/or VIIIth cranial nerves. Ten patients with trigeminal neuralgia (n = 8), hemifacial spasm (n = 1), or intractable tinnitus (n = 1) underwent primarily microvascular decompression procedures. One patient with geniculate neuralgia underwent nervus intermedius sectioning combined with microvascular decompression. Eight patients underwent unilateral vestibular nerve neurectomies for treatment of Meniere's disease. A 0- or 30-degree rigid endoscope was used in conjunction with the standard microscopic approach for all procedures. All patients experienced resolution or significant improvement of their preoperative symptoms after posterior fossa surgery. The endoscope allowed improved definition of anatomic neurovascular relationships without the need for significant cerebellar or brainstem retraction. Cleavage planes between the cochlear and vestibular nerves entering the internal auditory canal and sites of vascular compression could not be microscopically observed for several patients; however, endoscopic identification was possible for all patients. There were no complications related to the use of the endoscope. The rigid endoscope can be used safely during posterior fossa surgery to treat cranial neuropathies, and it allows improved observation of the cranial nerves, nerve cleavage planes, and vascular anatomic features without significant cerebellar or brainstem retraction.

The Extreme Lateral Transcondylar Approach to Aneurysms of the Vertebrobasilar Junction, the Vertebral Artery, and the Posterior Inferior Cerebellar Artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.

The far lateral/combined supra- and infratentorial approach. A human cadaveric prosection model for routes of access to the petroclival region and ventral brain stem.

A far lateral approach to the ventral brain stem, lower clivus, and anterior foramen magnum is described. Methods for further exposure of the superior petroclival region by incorporating a subtemporal craniotomy and posterior petrosectomy are also demonstrated. Eight sequentially illustrated steps depict this technique. The far lateral/combined supra- and infratentorial exposure is a comprehensive surgical approach that provides direct access to the entire anterior and lateral brain stem and craniovertebral junction. It minimizes brain-stem retraction and maximizes visualization of the neurovascular structures.

Foramen Magnum Meningioma and Arachnoid Cyst Coinciding in the Lateral Cerebellomedullary Cistern —Case Report—

An extremely rare foramen magnum meningioma associated with an arachnoid cyst in the lateral cerebellomedullary cistern occurred in a 65-year-old female presenting with dizziness. Neuroimaging revealed a meningioma at the left lateral edge of the foramen magnum and an arachnoid cyst mainly located in the right lateral cerebellomedullary cistern, compressing the medulla oblongata bilaterally. After fenestration of the cyst wall and tumor removal, the clinical symptoms ameliorated. We recommend that where a foramen magnum tumor coexists with an arachnoid cyst of the posterior fossa, the tumor should be removed after shrinking the cyst to obviate the need for brainstem retraction.

The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction

The authors review their experience with a dorsolateral approach to the anterior rim of the foramen magnum and adjacent region. The operative technique includes exposure of the vertebral artery at C1, partial resection of the occipital condyle and lateral atlantal mass, and extradural drilling of the jugular tubercle. This approach has been applied in six patients who harbored intradural space-occupying lesions located ventral to the lower brain stem. Excision of the neoplasm was virtually total in all but one patient, in whom biopsy was the primary goal of the intervention. No morbidity and no mortality were associated with this approach. The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction.

The Dorsolateral, Suboccipital, Transcondylar Approach to the Lower Clivus and Anterior Portion of the Craniocervical Junction

Abstract The authors review their experience with a dorsolateral approach to the anterior rim of the foramen magnum and adjacent region. The operative technique includes exposure of the vertebral artery at C1, partial resection of the occipital condyle and lateral atlantal mass, and extradural drilling of the jugular tubercle. This approach has been applied in six patients who harbored intradural space-occupying lesions located ventral to the lower brain stem. Excision of the neoplasm was virtually total in all but one patient, in whom biopsy was the primary goal of the intervention. No morbidity and no mortality were associated with this approach. The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction.

The clinical significance of the P15 wave of the somatosensory evoked potential in tentorial herniation.

Somatosensory evoked potentials (SEPs) to median nerve stimulation and auditory brainstem evoked potentials (BAEPs) were recorded in 16 comatose patients who had suffered transtentorial herniation (TH) due to intracranial haematoma, hydrocephalus or tumour. An attempt was made to correlate the changes in the N14-P15 component of the central conduction time (CCT) and the I-V interpeak latencies (IPLs) of the BAEP with the clinical severity of TH. The N14-P15 component was not affected in seven patients at the diencephalic or early third-nerve stage, and six of these seven showed normal I-V IPLs. All six patients at the late third-nerve/midbrain stage or worse, however, showed abnormalities in the N14-P15 components. Interestingly, five patients showed dissociation of SEP and BAEP abnormalities suggesting a differential sensitivity of the medial and lateral lemnisci in the brainstem to ischaemia and/or compression. All five patients in whom the P15 potential was absent on either side had a poor outcome and there was a correlation between the electrical failure in the N14-P15 component and the degree of brainstem damage caused by TH as assessed clinically. Reversible loss of the P15 potential by brainstem retraction has been shown in intraoperative SEP monitoring during aneurysm surgery. Prolonged compression of the upper brainstem seems to cause irreversible loss of the P15 which should be regarded as being due to irrecoverable brainstem dysfunction.

Brain stem auditory evoked potentials in posterior circulation surgery.

The objectives of this study were to evaluate the use of brain stem auditory evoked potentials (BAEPs) in 10 adult patients with vascular disorders of the posterior circulation that were treated surgically and to compare the BAEPs with the neurological findings. The vascular lesions included basilar artery stenosis in 3 patients, vertebral artery stenosis in 1 patient, brain stem/cerebellar arteriovenous malformation in 2 patients, and basilar artery aneurysm in 4 patients. Measurement of BAEPs were carried out during operation in all cases. Eight patients had BAEPs measured before operation, and 9 patients had BAEPs measured after operation. Repeat postoperative studies were performed in patients with changes in neurological status. In general, BAEP abnormalities correlated with the neurological findings before and after operation. Six patients had normal intraoperative studies. None of them had clinical findings of pontomesencephalic dysfunction after operation. Three patients with significant BAEP abnormalities during operation had neurological findings of pontomedullary ischemia after operation. Transient BAEP changes in 1 patient were thought to be the result of brain stem retraction. The BAEPs were lost in 3 patients who died. The use of BAEP measurement did not lengthen the operative procedures. However, the technique used in this study required 4 to 8 minutes for the accumulation and interpretation of each average, thereby delaying feedback to the surgeon. The results of this study suggest a potential role for BAEP monitoring in identifying brain stem injury during posterior circulation surgery.