Gamma knife surgery for mesial temporal lobe epilepsy

Object. Gamma knife radiosurgery (GKS) allows precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without causing significant radiation damage to adjacent tissues. Almost all the well-documented cases of radiosurgery for epilepsy are for epilepsies associated with space-occupying lesions. These results prompted the authors to investigate the use of radiosurgery as a new way of treating epilepsy not associated with space-occupying lesions. Methods. To evaluate this new method, 25 patients who presented with drug-resistant mesial temporal lobe epilepsy (MTLE) were selected. A follow up of more than 24 months is now available for 16 patients. The preoperative evaluation was performed as it usually is in patients selected for microsurgery for MTLE. In lieu of microsurgery, the treatment of amygdalohippocampal structures 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). Morphological changes on magnetic resonance imaging were visible at II months (median) after GKS (range 7-22 months). During the onset period of these radiological changes, three patients experienced headache associated, in two cases, with nausea and vomiting. In these three patients the signs resolved immediately after prescription of low doses of steroids. No cases of permanent neurological 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 middle-term efficiency and safety when using GKS to treat MTLE. Further long-term follow up is required. It seems that the introduction of GKS into epilepsy treatment can reduce the invasiveness and morbidity.