Abstracts

RATIONALE:_Drug resistant epilepsy associated with Hypothalamic Hamartomas (HH) can be cured by microsurgical resection of the lesion. Morbimortality risk of microsurgery in this area is significant. Gamma Knife Surgery (GKS) reduced invasivity seems to be well adapted in this indication. METHODS:_In order to evaluate the safety and efficacy of GKS in this infrequent pathology we organized a multicenter retrospective study. Ten patients were treated in 7 different centers. The follow-up was superior to 12 months for the 8 patients with a median follow up of 28 months (mean 35 range 12-71months). All patients had severe drug-resistant epilepsy including frequent gelastic and generalized tonic or tonicoclonic attacks. Median age was 18,5 (range 2-34) and 3 patients had precocious puberty. All patients had sessile HH. The median marginal dose was 15,25 Gy (range 12-20). Two patients were treated two times (at 19 and 49 months) due to unsufficient efficacy. RESULTS:_All the patients were improved. Four patients were seizure free, one had rare nocturnal seizures, one had some rare partial seizures and no more generalized attacks and two were only improved with a reduction in frequency of seizures but persistance of some rare generalized seizures. A clear correlation between efficacy and dose was observed in this series. The marginal dose was superior to 17 Gy for all the patients in the successful group and inferior to 13 Gy for all the patients in the " improved " group. No side effect was reported except for pokilothermia in one patient. Behavior was clearly improved in two patients (with only slight improvement of their epilepsy). Complete coverage of the HH did not seem to be mandatory since in two patients from the successful group, the dosemetry spared a significant part of the lesion. CONCLUSIONS:_We report the first series demonstrating that GKS can be a safe and effective treatment of epilepsy when related to HH. We advocate marginal doses superior or equal to 17 Gy and partial dose planning when necessary for avoidance of critical structures. Due to high mortality morbidity risk with microsurgical resection we speculate that GKS will become the reference treatment.