Stereotactic radiosurgery in the management of angiographically occult vascular malformations

Purpose: To evaluate the role of stereotactic radiosurgery in the treatment of angiographic ally occult vascular malformations (AOVMs). Methods and Materials: From 1987 to 1996, 21 patients, 10 males and II fema les, median age of-II years (range: 7-75 years), with an intracerebral AOVM underwent stereotactic radiosurgery at our institution. All were considere d at high risk for surgical intervention. The vascular lesions were located in the brainstem (17 patients), basal ganglia (2), occipital lobe (1), and cerebellum (1), Diagnosis was based on high-resolution magnetic resonance imaging (MRI). Clinical presentation at onset included previous intracerebr al hemorrhage (20 patients) and epilepsy (1). All patients were treated wit h a linac-based radiosurgical technique. The median dose delivered was 25 G y (range 13-50 Gy), typically prescribed to the 80-90% isodose surface (ran ge 50-90%), which corresponded to the periphery of the vascular malformatio n. Patients were followed by clinical neurologic assessment and by MRI on a regular interval basis. Results: Follow-up was obtained in 20 patients; clinical or MRI information was not available for 1 patient, and this patient was excluded from our an alysis. At a median follow-up of 77 months (range: 4-141 months), follow-up MRIs postradiosurgery do not demonstrate any changes in the appearance of the AOVM. Four patients developed an intracranial bleed at 4, 8, 35, and 57 months postradiosurgery, Annual hemorrhage rates were considerably higher in the observation period preradiosurgery than postradiosurgery (30% vs. 3. 2%,p < 0.001). Complications postradiosurgery were observed in 4 patients. Three patients developed mild to moderate edema surrounding the radiosurgic al target, expressed at 5, 8, and 24 months, respectively. In all cases, th e edema was transient and resolved completely on subsequent MRIs. One of th e 4 patients developed radiation necrosis 8 months after radiosurgery, Conclusion: The use of stereotactic radiosurgery in the treatment of AOVM c ontinues to be controversial. Our results appear to show a reduction in the risk of symptomatic hemorrhage post treatment. Patients with previous hist ory of hemorrhage or progressive neurologic deficit and small, well circums cribed lesions may benefit from a trial of stereotactic radiosurgery. (C) 2 001 Elsevier Science Inc.