NeoplasmsStereotactic radiosurgery for anterior foramen magnum meningiomas
Section snippets
Clinical materials and methods
Between August 1987 and April 1997, five patients (three men and two women) with foramen magnum meningiomas underwent stereotactic radiosurgery with the 201-source cobalt-60 gamma knife at the Center for Image-Guided Neurosurgery, University of Pittsburgh. Three patients had radiosurgery as their primary procedure and two patients had radiosurgery for a recurrence of their previously operated foramen magnum meningioma. All patients had been rejected for either initial or repeat surgical
Case 1
An 82-year-old female with a history of congestive heart failure presented with difficulty in walking and ataxia. Imaging confirmed a meningioma in the region of the anterior foramen magnum. Neurological examination revealed a broad-based ataxic gait, impaired tandem walking, and positive Romberg sign. She declined open surgical resection and was referred for Gamma Knife radiosurgery. The tumor had a volume of 12 ml. She was treated with a maximum dose of 30 Gy, tumor margin dose of 15 Gy with
Case 2
An 81-year-old male presented with a 5-year history of cervical pain and a 2-month history of progressive upper extremity numbness and weakness combined with increasing lower extremity spasticity. Neurologic examination demonstrated weakness of the right arm with increased reflexes, patchy sensory loss and marked spasticity of the lower extremities with associated ankle and patellar clonus. He underwent posterior fossa craniectomy and upper cervical laminectomy followed by partial tumor
Case 3
An 81-year-old man with a history of dysequilibrium and vertigo had undergone craniotomy 3 years before presentation for a large foramen magnum-clival meningioma. At presentation he had a memory deficit and disturbance of equilibrium. MRI scans showed hydrocephalus and a large tumor measuring 18.5 ml in volume. The maximum tumor dose was 25 Gy and the tumor margin dose was 10 Gy (40% isodose). Eight isocenters of irradiation were used using a combination of three 18-mm, on 14-mm, and four 8-mm
Case 4
A 73-year-old woman had a history of pituitary tumor for which she underwent two resections and radiation therapy. She developed a foramen magnum meningioma that gradually enlarged on serial imaging studies. Radiosurgery was performed for a tumor volume of 1.8 ml. The tumor received a maximum dose of 28 Gy and a margin dose of 14 Gy using five 8 mm isocenters. At follow-up 1 year later she was clinically unchanged and the tumor volume was stable.
Case 5
An 84-year-old man developed progressive limb weakness, decreased hearing, diplopia, and hoarseness of voice. MRI revealed a foramen magnum and clival tumor measuring 4.6 ml in volume. In view of his age, surgery was deemed too high a risk. Radiosurgery was performed using a maximum dose of 32 Gy and a margin dose of 16 Gy with two isocenters of irradiation (one 18-mm and one 8-mm collimator) (Figure 3). Four and half years after treatment, follow-up imaging showed a reduction in the size of
Discussion
Foramen magnum meningiomas are relatively rare lesions. Yasuoka et al reported an incidence of 3.2% among 1139 meningiomas encountered during a 20-year period [25]. These tumors pose a formidable challenge to surgeons because of their anterior location that prevents easy access to the tumor. In addition, adjacent critical neural and vascular structures may be injured during the course of tumor removal or exposure. Initial neurosurgical experience suggested that the lower cranial nerves and
The role of radiosurgery
Radiosurgery for meningiomas in other locations has provided safe and effective tumor control with follow-up that now extends to 10 years 7, 11, 14, 15, 17, 21. The twin goals of radiosurgery are tumor control and reduced morbidity. In all five patients in this series these goals were acheived. No patient showed growth of the tumor or additional neurological deficits attributable to radiosurgery. No patient showed imaging signal changes in the adjacent brainstem or spinal cord. We believe that
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