Effect of Radiosurgery on Symptomatic Epilepsy

ABSTRACT

It has been suggested that focused radiation generated and delivered by several means can reduce seizure frequency in idiopathic and lesional epilepsy. Stereotactic radiosurgery has become one of the most acceptable means of treating intracranial arteriovenous malformations or tumors, and has been found to have an effect on seizures serendipitously while being used for other indications. Between 1988 and 1996, 595 lesions of 490 patients with AVM or brain tumors were treated with radiosurgery(55 by Linear accelerator, 545 by Gamma Knife). Lesional epilepsy was accompanied in 73 patients before treatment. Among them, 24 cases had chronic repeated seizure(more than 4 times per 1 year over 1 year) and were on anticonvulsants before treatment, and were followed longer than 1 year. The lesion volume was 2.9-27.9cc(mean, 16.2+/-15.1cc). The estimated dose was 10-26.4Gy(mean, 15.9+/-4Gy) at the margin. Mean follow-up is 20 months(from 12 to 42.3). Epilepsy worsened transiently in 2 cases due to radiation induced imaging changes that were improved with steroid medication. Four cases were seizure-free after treatment. Six patients presented a reduction of seizure frequencies by more than 50%. Reduction of the lesion volume did not correlate with the reduction of seizures. However, the mean volume of preoperative lesions in improved cases(19.3+/-2.8cc) was larger than in unimproved cases(13.1(8.2cc) and it was the only statistically significant variable. It seems that radiosurgery employing a standard neuro-oncological dose can improve seizures and this effect is not related to the lesion volume reduction.