Gamma knife radiosurgery of meningiomas involving the foramen magnum

BACKGROUND: Foramen magnum meningiomas represent a challenging clinical entity. Although resection is performed for those with a mass effect, complete resection is not always feasible. For some patients, stereotactic radiosurgery may be used as the primary treatment modality. We evaluatedthe long-term outcome of Gamma Knife radiosurgery (GKRS) for the treatment of patientswith a foramen magnum meningioma. MATERIALS AND METHODS: Between 1991 and 2005, 222 patients with a meningioma in the posterior fossa were treated with GKRS at the University of Virginia. Of these patients, 5 had meningiomas involving the foramen magnum. At the time of GKRS, the median age of the patients was 60 years (range, 51–78). Three patients were treated with radiosurgery following an initial resection and 2 were treated with upfront radiosurgery. The patients were assessed clinically and radiologically at routine intervals following GKRS. RESULTS: The median tumor volume was 6.8 cc (range 1.9–17 cc). The GKRS tumor received a marginal dose of 12 Gy (range 10–15), and the median number of isocenters was 5 (range 3–19). The mean follow-up was 6 years (range 4–13). One lesion increased in size following GKRS requiring a second treatment, resulting in size stabilization. At the time of the last follow-up, all meningiomas had either demonstrated no growth (n = 4) or reduction in size (n = 1). No patients experienced post-radiotherapy complications. CONCLUSIONS: GKRS affords a high rate of tumor control and preservation of neurologic function for patients with foramen magnum meningiomas. Further study of its role in the neurosurgical management of such patients seems warranted.