Foramen magnum meningiomas: detailed surgical approaches and technical aspects at Lariboisière Hospital and review of the literature

Abstract

Foramen magnum meningiomas are challenging tumors, requiring special considerations because of the vicinity of the medulla oblongata, the lower cranial nerves, and the vertebral artery. After detailing the relevant anatomy of the foramen magnum area, we will explain our classification system based on the compartment of development, the dural insertion, and the relation to the vertebral artery. The compartment of development is most of the time intradural and less frequently extradural or both intraextradural. Intradurally, foramen magnum meningiomas are classified posterior, lateral, and anterior if their insertion is, respectively, posterior to the dentate ligament, anterior to the dentate ligament, and anterior to the dentate ligament with extension over the midline. This classification system helps to define the best surgical approach and the lateral extent of drilling needed and anticipate the relation with the lower cranial nerves. In our department, three basic surgical approaches were used: the posterior midline, the postero-lateral, and the antero-lateral approaches. We will explain in detail our surgical technique. Finally, a review of the literature is provided to allow comparison with the treatment options advocated by other skull base surgeons.

Versatility of sub-occipital approach for foramen magnum meningiomas: a single centre experience

“…In his series, worsening of neurological condition is reported in 7.5%. In our experience, with limitation to a few cases, we report two complications (1,5,15).…”

Posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: quantitative anatomical study using three-dimensional computed tomography angiography

“…Even in a far lateral or extreme lateral approach, which often requires identification or mobilization of the VA, the measurements in this study may have limited usefulness because the anatomical relationship of the VA to the posterior arch of the atlas are modified by rotation of the head in surgical positioning. 3,12 However, the quantification of the protrusive course of the VA performed in the present study can serve to alert the surgeon to the possibility of an irregular course of the VA, irrespective of patient's age or disease.…”

The far-lateral approach for foramen magnum meningiomas

“…2,8,28,33,41,44,47,49 Some authors advocate the need for preoperative embolization of arterial feeders to minimize intraoperative bleeding and operative time; complete 6-vessel angiography would be mandatory in those situations, because the majority of those lesions have arterial feeders derived from external carotid circulation or extracranial VA. However, this has not been the practice at our institution.…”

“…At the level of the most superior dentate ligament, the VA is surrounded by a periosteal sheath that invaginates into the foramen magnum lateral dura and forms a fibrous ring. 8 The origin of the ipsilateral posterior spinal artery and the distal portion of the first cervical nerve can sometimes be found inside this sheath. 11,36,37 The PICA can have an extracranial extradural origin in 5%-20% of the cases.…”

“…However, anterior or anterolateral lesions were associated with increased surgical morbidity, due to medullary tissue retraction needed for adequate exposure. 2,5,8,14,15,23,26,31,41,42,44,47 In 1988, George et al 14 described the far-lateral approach for lesions involving the anterior portion of the foramen magnum, similar to the technique described by Heros 21 for treatment of vertebral and vertebrobasilar lesions. Since then, the far-lateral approach and its variants has become an essential technique for neurosurgeons treating lesions involving the lower clivus or the foramen magnum.…”