Radiosurgery of epilepsy. Long-term results.

Based on experimental research, since 1982 until 1991 a series of 11 patients diagnosed as suffering from idiopathic focal epilepsy have been treated with stereotactic radiosurgery. Focus location was determined with cortical electrodes and confirmed by stereotactically placed deep electrodes. Stereotactic radiosurgery was performed with photons from a cobalt source with a dose of 10 to 20 Gy, except in two cases in whom a betatron was used. The results were: complete cessation of seizures in four cases and a significant reduction in the number of seizures in five additional cases. Seizures began to decrease gradually after a period of three months of one year, except in two cases in whom there was an immediate response after treatment. In two cases there was no change. No complication related to the irradiation was recorded. The gradual and delayed effect, obtained with low doses, may favour the hypothesis that non-descructive permanent structural changes, possibly related to the neuronal plasticity phenomenon, constitute the mechanism underlying these facts. Although the number of cases so far is too small, the absence of side-effects may make this bloodless method the one of choice specially in those cases in whom eloquent areas are involved.