Long-term outcome of gamma-knife surgery in temporal lobe epilepsy

Indication of gamma-knife surgery (GKS) in temporal lobe epilepsy (TLE) remains a matter of debate. Either positive or negative results have been reported in studies with a maximum follow-up of 24 months. No long-term data have been published yet.

We collected data from 15 TLE patients who underwent GKS and whose follow-up was longer than 24 months. Localisation and extension of the epileptogenic zone (EZ) were assessed by SEEG in eight patients. Ten patients were presenting with mesial TLE (mTLE) while in the other five SEEG showed that the EZ was extending beyond mesio-temporal structures. GKS procedure was targeted to the EZ at a dose of 21.1+/-2.6Gy at the margin.

The mean duration of the follow-up was 60+/-22.3 months. At last follow-up, seven patients (46.7%) were free of disabling seizure. The last seizure following GKS occurred on average after a delay of 19.75+/-20.62 months. No patient suffered recurrent seizures after a long period free of disabling seizures. No significant prognostic predictor could be individualized in this population. However, 6 of the 10 patients with mTLE (60%) were seizure free whereas only 1 of the 5 (20%) whose EZ was more extended exhibited the same seizure outcome.

When a positive outcome is achieved, the risk of seizure recurrence remains low at long term. In patients with typical mTLE, long-term GKS results may be closed to those observed after conventional surgery. Conversely, this procedure should not be proposed to patients in whom SEEG results suggest that the EZ is not restricted to mesial temporal structures.