Results of γ-Knife Radiosurgery of Brain Arteriovenous Malformations

Abstract

Between 1992 and 1996 γ-knife radiosurgery was performed on 192 patients with the diagnosis of brain intracerebral arteriovenous malformations (AVM) at Na Homolce Hospital, Prague. The largest diameter of the nidus ranged between 0.6–5.4 cm, median 2.2 cm. The nidus volume ranged 0.15–28.6 cm², median 3.9 cm². Thus far, the angiographic evaluation after radiosurgery was performed in 162 patients. The treatment result reference was defined as follows: the interval with a lower limit represented by the percentage of the complete obliteration in the whole group of patients and the upper limit represented by the percentage of the obliteration only in the group of patients with control angiography. The total obliteration of the AVM 1 year after radiosurgery was reached in 18–32% patients, after 2 years in 59–72%, after 3 years in 69–81%, and 4 years after radiosurgery in 71–93% patients. The morbidity of radiosurgery was 6% and, in a majority of the cases, was caused by the postirradiation edema and resolved after corticotherapy. The improvement of secondary epilepsy was observed in 35% of the patients and the improvement of the neurological status in 50%. The mortality of radiosurgical procedure itself was zero. The risk of mortality of the patients with AVM treated with the γ-knife was related to the latent period from treatment until complete obliteration. This period took between 1–3 years when the natural risk of the repeated hemorrhage was the same as that in the nontreated patient. The rebleeding occurred in eight patients; three of them died and five patients were without neurological sequela. If the obliteration did not occur up to 3 years after the γ-knife radiosurgery, reirradiation was indicated. AVM of Spetzler grade I–III proved to have a high rate of obliteration after γ-knife radiosurgery, while only one-third of patients with Spetzler grade IV obliterated after the first radiosurgery. Radiosurgery was not indicated for AVMs Spetzler grade V. AVMs with an average diameter up to 3 cm were good indications for primary radiosurgery as a noninvasive treatment. In AVMs with the average diameter larger than 3 cm, radiosurgery, microsurgery, and embolization are the methods of choice and the radical treatment may require an adequate combination of these methods.