Foramen Magnum Meningiomas: A Review from Personal Experience of 37 Cases and from a Cooperative Study of 106 Cases

Summary: Foramen magnum (FM) meningiomas are reviewed from our personal experience of 37 cases over 12 years and a cooperative study done in 1993 in which patients were collected from 21 French departments of neurosurgery over the period 1982–1992. FM meningiomas account for 6.5% of posterior fossa meningiomas and 1.5% of all intracranial meningeal tumors. Historical background and clinical features are presented first. Then reported are the histological and radiological data. Finally, the surgical technique is described, detailing postoperative clinical condition and extent of resection. Important specific points are emphasized: (a) the limits of what is defined as the FM area, which is generally not described in the literature; (b) the high frequency (56%) of psamommatous tumors; and (c) the great value of magnetic resonance imaging (MRI) and angio-MRI in defining the localization regarding the dura (14% of FM meningiomas have an extradural extension), the vertebral artery (48% of FM meningiomas are developed above the vertebral artery), and the anteroposterior location (31% of FM meningiomas are anterior and 56% are lateral). These points are fundamental to choosing the best surgical technique. The technique always includes drilling of the FM lateral wall according to tumor localization, thus providing lateral access to the premedullary spaces. This lateral approach can be posterolateral (a lateral extension of the standard midline approach mainly used to excise intradural tumors) or anterolateral (applied in the excision of extradural tumors). The lateral approach is currently the technique that permits the most complete resection (96%) with minimal mortality and morbidity.