Gamma Knife Radiosurgery of The Brain Stem Cavernous Angioma

From December 2001 to December 2007, twenty one patients with symptomatic brainstem cavernous angioma were treated using the Leksell gamma knife. The median marginal dose was 15 Gy (range 13~18 Gy) at 50% isodose (range 45~80%). Mean follow up period was 33 months (range 4~67 months). Symptomatic improvement was achieved in 14 (66.6%) patients. There were 5 (23.8%) patients with neurological deterioration during follow-up period. Among them one patient aggravated due to overt bleeding and radiation effect was thought be the cause of deterioration in the others. Two patients needed surgical treatment subsequently and the other three patients improved with conservative management. Digital volumetry was performed before and after GKS with mean interval of 17 months (range 5~51 months). Mean volume of the lesions was 1155.6 $mm^3$ (range 130.7~3800 $mm^3$) before GKS and 724.8$mm^3$ (range 36.8~1322 $mm^3$) at the last follow-up. Volume of the lesion decreased in 17 patients (81.0%). GKS is an effective treatment modality for brainstem cavernous angioma in surgically unfavorable location. However, neurological deterioration after GKS was not rare (23%), particularly within 1 yr after GKS. It is necessary to be cautious in dose prescription.