Gamma knife surgery for epilepsy related to hypothalamic hamartomas

OBJECTIVE: Drug-resistant epilepsy associated with hypothalamic hamartomas (HHs) can be cured by microsurgical resection of the lesions. Morbidity and mortality rates for microsurgery in this area are significant. Gamma knife surgery (GKS) is less invasive and seems to be well adapted for this indic ation. METHODS: To evaluate the safety and efficacy of GKS to treat this uncommon pathological condition, we organized a multicenter retrospective study. Ten patients were treated in seven different centers. The follow-up periods we re more than 12 months for eight patients, with a median follow-up period o f 28 months (mean, 35 mo; range, 12-71 mo). All patients had severe drug-re sistant epilepsy, including frequent gelastic and generalized tonic or toni coclonic attacks. The median age was 13.5 years (range, 1-32 yr; mean, 14 y r) at the time of GKS. Three patients experienced precocious puberty. All p atients had sessile HHs. The median marginal dose was 15.25 Gy (range, 12-2 0 Gy). Two patients were treated two times (at 19 and 49 mo) because of ins ufficient efficacy. RESULTS: All patients exhibited improvement. Four patients were seizure-fre e, one experienced rare nocturnal seizures, one experienced some rare parti al seizures but no more generalized attacks, and two exhibited only improve ment, with reductions in the frequency of seizures but persistence of some rare generalized seizures. Two patients, now seizure-free, were considered to exhibit insufficient improvement after the first GKS procedure and were treated a second time. A clear correlation between efficacy and dose was ob served in this series. The marginal dose was more than 17 Gy for all patien ts in the successful group and less than 13 Cy for all patients in the "imp roved" group. No side effects were reported, except for poikilothermia in o ne patient. Behavior was clearly improved for two patients (with only sligh t improvements in their epilepsy). Complete coverage of the HHs did not see m to be mandatory, because the dosimetry spared a significant part of the l esions for two patients in the successful group. CONCLUSION: We report the first series demonstrating that GKS can be a safe and effective treatment for epilepsy related to HHs. We advocate marginal doses greater than or equal to 17 Gy and partial dose-planning when necessa ry, for avoidance of critical surrounding structures.