GAMMA-KNIFE RADIOSURGERY IN 11 HEMANGIOBLASTOMAS

One suprasellar, one mesencephalic, and nine cerebellar hemangioblasto mas were treated with the gamma knife in 10 patients (median age 48 ye ars) in Stockholm between 1978 and 1993. Four patients had von Hippel- Lindau dis ease, a dominant inherited trait predisposing to multiple h emangioblastomas. Six hemangioblastomas were treated with radiotherapy at a median margin dose of 25 Gy (20-35 Gy) before 1990 and the next five with a median of 10 Gy (5-19 Gy). Computerized tomography or magn etic resonance images were available for 10 of the 11 hemangioblastoma s at a median follow-up time of 26 months (4-68 months) after radiosur gery. The solid part of six hemangioblastomas shrank in a median of 30 months, whereas four hemangioblastomas were unchanged at a median of 14 months. Five hemangioblastomas had an adjoining cyst and three of t hese cysts had to be evacuated after radiosurgery. One solitary hemang ioblastoma later developed a de novo cyst that also needed evacuation. One patient with two cerebellar hemangioblastomas (margin dose 25 Gy each) developed edema at 6 months and required a shunt and prolonged c orticosteroid treatment. The combined follow-up data of the 23 hemangi oblastomas in 15 patients from previous literature and the present ser ies indicate that, first, a solitary small- or medium-sized hemangiobl astoma usually shrinks or stops growing after radiosurgery. The recomm ended margin dose is 10 to 15 Gy. Second, the adjoining cyst often doe s not respond to radiosurgery but requires later, sometimes repeated e vacuation.