Gamma knife surgery for mesial temporal lobe epilepsy

Object. Gamma knife radiosurgery (GKS) allows precise and complete destruct ion of chosen target structures containing healthy and/or pathological cell s, without causing significant radiation damage to adjacent tissues. Almost all the well-documented cases of radiosurgery for epilepsy are for epileps ies associated with space-occupying lesions. These results prompted the aut hors to investigate the use of radiosurgery as a new way of treating epilep sy not associated with space-occupying lesions. Methods. To evaluate this new method, 25 patients who presented with drug-r esistant mesial temporal lobe epilepsy (MTLE) were selected. A follow up of more than 24 months is now available for 16 patients. The preoperative eva luation was performed as it usually is in patients selected for microsurger y for MTLE. In lieu of microsurgery, the treatment of amygdalohippocampal s tructures was performed using GKS. Thirteen (81%) of these 16 patients are seizure free, and two are improved. The median latent interval from GKS to seizure cessation was 10.5 months ( range 6-21 months). Two patients were immediately seizure free. The median latency in aura cessation was 15.5 months (range 9-22 months). Morphologica l changes on magnetic resonance imaging were visible at II months (median) after GKS (range 7-22 months). During the onset period of these radiologica l changes, three patients experienced headache associated, in two cases, wi th nausea and vomiting. In these three patients the signs resolved immediat ely after prescription of low doses of steroids. No cases of permanent neur ological deficit (except three cases of nonsymptomatic visual field deficit ), or morbidity, or mortality were observed. Conclusions. This initial experience indicates that there is short- to midd le-term efficiency and safety when using GKS to treat MTLE. Further long-te rm follow up is required. It seems that the introduction of GKS into epilep sy treatment can reduce the invasiveness and morbidity.