Ossama Al-Mefty

Petrosal approach for petroclival meningiomas.

Thirteen patients harboring large petroclival meningiomas are reported. The evolution of the petrosal approach is discussed, and modifications for improvement in surgical technique are described. There was no mortality in this series, and total removal was achieved in all but two patients. Morbidity included cranial nerve deficit, pulmonary embolism, and hemiparesis.

Fiber Dissection Technique: Lateral Aspect of the Brain

OBJECTIVE The fiber dissection technique involves peeling away the white matter tracts of the brain to display its three-dimensional anatomic organization. Early anatomists demonstrated many tracts and fasciculi of the brain using this technique. The complexities of the preparation of the brain and the execution of fiber dissection have led to the neglect of this method, particularly since the development of the microtome and histological techniques. Nevertheless, the fiber dissection technique is a very relevant and reliable method for neurosurgeons to study the details of brain anatomic features. METHODS Twenty previously frozen, formalin-fixed human brains were dissected from the lateral surface to the medial surface, using the operating microscope. Each stage of the process is described. The primary dissection tools were handmade, thin, wooden spatulas with tips of various sizes. RESULTS We exposed and studied the myelinated fiber bundles of the brain and acquired a comprehensive understanding of their configurations and locations. CONCLUSION The complex structures of the brain can be more clearly defined and understood when the fiber dissection technique is used. This knowledge can be incorporated into the preoperative planning process and applied to surgical strategies. Fiber dissection is time-consuming and complex, but it greatly adds to our knowledge of brain anatomic features and thus helps improve the quality of microneurosurgery. Because other anatomic techniques fail to provide a true understanding of the complex internal structures of the brain, the reestablishment of fiber dissection of white matter as a standard study method is recommended.

The “Subdural” Space

ABSTRACTTHIS REVIEW CONSIDERS the structure of the meninges, as seen at the electron microscopic level, with particular emphasis on the dura-arachnoid junction and whether a naturally occurring space is found at this interface. The classic view has been that a so-called subdural space is located bet

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.

Hyperostosis associated with meningioma of the cranial base : Secondary changes or tumor invasion

OBJECTIVE Hyperostosis associated with intracranial meningiomas is a well-described entity. The cause, management, and prognosis of these bony changes have long been a point of controversy. Some authors have postulated that hyperostotic changes are secondary to the formation of the tumor and do not constitute invasion of the tumor into the bone. Determining this point has direct implications in the treatment of these patients, especially regarding surgical considerations. To more thoroughly evaluate this question, a study correlating the morphology to the radiology is necessary. METHODS In this study, 51 patients underwent resection for meningiomas involving the cranial base. Preoperative radiographic evaluation using magnetic resonance imaging and/or computed tomography was performed, and areas of hyperostosis were identified. During the resection of the tumor, biopsies from these hyperostotic regions were sent for histological evaluation regarding the presence or absence of tumor invasion of the bone. RESULTS Preoperative neuroradiological assessment identified 26 patients with radiographic evidence of hyperostosis. Histological examination of the resected bone showed tumor invasion in 35 patients, including the area of radiographically identified hyperostosis in 25 of the 26 patients. The floor of the middle fossa was a specific area of low sensitivity for preoperative assessment of associated hyperostosis. CONCLUSION These results indicate that hyperostosis associated with meningiomas involving the cranial base are caused by tumor invasion of the bone histologically.

Chordoma and chondrosarcoma: Similar, but quite different, skull base tumors

Chordoma and chondrosarcoma of the skull base are frequently amalgamated because of similar anatomic location, clinical presentation, and radiologic findings. The chondroid chordoma variant has been reported to carry a better prognosis. The objective of the current study was to investigate the distinctions between these 3 entities.

Vascular considerations and complications in cranial base surgery.

The technical evolution of cranial base surgery has resulted in approaches that allow more radical surgical extirpation of complex cranial base lesions. Our service has extensively applied these cranial base approaches for lesions of the cranial base. A subgroup of 100 patients who had cranial base tumors involving potential manipulation or sacrifice of carotid arteries underwent 20-minute balloon test occlusions coordinated with vascular assessments consisting of a combination of the following: 1) four-vessel cerebral angiogram with compression studies; 2) occlusion transcranial Doppler ultrasonography; 3) occlusion single-photon emission computed tomography perfusion studies; and 4) xenon-133 cerebral blood flow studies. Transient neurological deficits associated with balloon test occlusion occurred in 7 of 100 patients (7%). Subsequently, 18 patients underwent permanent carotid occlusion by endovascular detachable balloons. Delayed ischemic complications (> 72 h) occurred in 4 of 18 (22%) patients. Additionally, a number of vascular complications not predicted by the balloon occlusion tests and vascular assessments were experienced. Repeat vascular assessments defined the causes and guided treatment of ischemic patients. Ischemic complications were caused by hemodynamic insufficiency, embolization, vasospasm, radiation vasculopathy, and venous anomaly. Our experience leads us to believe that no vascular assessment exists today that can predict the occurrence of vascular complications accurately. The current enthusiasm for cranial base surgery must be tempered with the sober reality that management of cerebrovascular anatomy and physiology remain significant limitations. Consideration of potential cerebrovascular complications is paramount to successful outcome and implementation of cranial base surgery.

Surgery of tumors invading the cavernous sinus

Potential injury to neurovascular structures within the cavernous sinus often prohibits total removal of various cranial base tumors. This report discusses the rationale of direct cavernous sinus surgery and describes a surgical technique refinement as evolved from experience in 18 histologically benign operative cases. The nature of tumor extension mandated entry to the sinus, either through the superior or lateral wall or both. The operative microscope facilitated dissecting and preserving the carotid artery and cranial nerves transversing the sinus. Venous bleeding was controlled by packing. There was one death unrelated to cavernous sinus surgery. Five patients, however, had complications related to cavernous sinus surgery, including hemiplegia in one patient and cranial nerve palsy in four.

Combined petrosal approach to petroclival meningiomas.

OBJECTIVE To study the use and advantages of combining the posterior petrosal approach with the anterior petrosal approach to petroclival meningiomas. METHODS Seven cases of petroclival meningiomas operated on via the combined petrosal approach were retrospectively analyzed. The basis on which this approach was selected was assessed, as were its benefits and risks. RESULTS Gross total resection was achieved in five of the seven patients. No mortality or decrease in Karnofsky performance score was observed at the time of the last follow-up examination. Six of the seven patients had serviceable hearing before the operation. Only one patient lost hearing after the operation, and this hearing loss occurred in only one ear. Before the operation, six patients were House-Brackmann facial nerve function Grade I, and one patient was Grade II to III. At the last follow-up examination, facial nerve function was Grade I in five patients, Grade II in one patient, and Grade V in one patient. Tumors in all patients involved the cavernous sinus, Meckel’s cave, petroclival junction, and middle clivus. All patients possessed a large posterior fossa component of tumor measuring an average of 3.6 × 3.5 × 4.2 cm. In four patients, the tumor was attached for the entire width of the clivus to the contralateral petroclival junction. Four patients displayed central brainstem compression. Four patients displayed bony changes at the petrous apex. All patients displayed total or partial encasement of the vertebrobasilar artery and its major branches. CONCLUSION The combined petrosal approach should be considered for patients who have a large petroclival meningioma and serviceable hearing. This approach enhances petroclival exposure and the degree of tumor resection, especially in the area of the petroclival junction, middle clivus, apical petrous bone, posterior cavernous sinus, and Meckel’s cave. The combined petrosal approach also allows better visualization of the contralateral side and the ventral brainstem, which facilitates safe dissection of the tumor from the brainstem, the basilar artery, and the perforators. If a patient has an early draining bridging vein to the tentorial sinus (before it reaches the transverse-sigmoid junction) or a prominent sigmoid sinus and jugular bulb, the combined petrosal approach provides significant working space.

Grade zero removal of supratentorial convexity meningiomas.

Although meningiomas are benign intracranial tumors, their frequency of recurrence after surgery has not been as low as expected. The recurrence rate of meningiomas is clearly related to the degree of tumor removal. Simpson Grade I removal, which entails excising the tumor and its dural and sinus attachments, is associated with the lowest rate of recurrence. To further minimize the recurrence of convexity meningiomas, we removed an additional dural margin of about 2 cm around the tumor (Grade 0 removal). For tumors involving bone, we removed the hyperostotic bone with a healthy margin and pericranium in en bloc resection. Between 1982 and 1992, 37 patients (15 men, 22 women) with an average age of 52.1 years were operated on by the above technique. Nineteen had a follow-up period of more than 5 years. To date, no tumors have recurred and no morbid incidences have occurred with this maneuver. We believe that the recurrence rate of convexity meningiomas can be diminished by including in the resection a margin of dura that might harbor a foci of tumor cells.