Gamma Knife Surgery For Hypothalamic Hamartomas Causing Refractory Epilepsy: Preliminary Results From A Prospective Observational Study

Keywords: hypothalamic hamartoma, gamma knife, epilepsy, outcome, radiosurgery

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     Hypothalamic hamartomas (HH) are congenital lesions typically presenting with medically-refractory epilepsy. Open or endoscopic surgical procedures to remove or disconnect the hamartoma have been reported to be effective but are associated with significant morbidity. Published studies of gamma knife radiosurgery for HH report encouraging rate of epilepsy resolution with minimal side effects.
     At the Centre Hospitalier Universitaire de Sherbrooke, we have undertaken a prospective observational study of the outcomes of patients who had radiosurgery for HH.
     Patients were included in the study if they had HH with refractory epilepsy and no other suspected seizure focus.
     After radiosurgery, seizure status was assessed every 3 months and reported using the Engel scale. Quality of life evaluation was performed using a standardized questionnaire (QOLIE-89) every year, and neuropsychological evaluation after 2 years.
     Nine patients have been included in the study. Age ranged from 12 to 57 years. Epilepsy began in infancy for all patients. Patients used an average of 2 antiepileptic drugs before radiosurgery. Using the Régis classification, 6 patients had smaller hamartomas (grade I-III) and underwent treatment of the entire lesion, using a margin dose of 14 to 20 Gy. Treatment volume ranged from 0.3 to 1.0 cc. Three patients had larger lesions (grade IV-VI) for which a radiosurgical disconnection was attempted, targeting the area of attachment to the hypothalamus. For those patients, the margin dose was 15 or 16 Gy, with treatment volume ranging from 0.8 to 1.8 cc. For all patients, the radiation dose received by the optic pathways was kept below 10 Gy.
     This is a retrospective study.
     Radiosurgery is safe and effective to control the epileptic disorder in HH patients when the entire lesion can be targeted, and should be a first-line therapy in medically-refractory patients.
     Radiosurgical disconnection is ineffective and cannot be recommended.


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