Abstracts

Rationale: Surgical intervention for HH has been limited due to modest outcomes (37- 50% seizure freedom), difficult location, and associated surgical morbidity (7-10% permanent). Seizures are primarily gelastic and may occur every few minutes, often progressing to intellectual deterioration, and behavioral impairment. The seizures are often not recognized early as they typically consist of mirthless laughter beginning early in infancy. Most patients fail appropriate trials with antiepileptic medications. We report seizure outcomes after completion of minimally invasive stereotactic laser ablation (SLA) procedure in five patients. Methods: After diagnosis, the parents were offered epilepsy surgery with a transcallosal craniotomy, a subfrontal endoscopic resection, stereotactic radiotherapy, or laser ablation. In all cases, they elected laser ablation and informed consent was obtained. An MR-compatible laser catheter (1.6mm dia) was navigated to the deep seated midline target with frame-based stereotaxy and a 3.2mm twist drill hole. An FDA-cleared laser surgery system (Visualase; Visualase, Inc., Houston, TX) was utilized to monitor the ablation process with real-time MRI thermometry. After confirmation test at 3W, higher doses of 6-10 W for 50-120 seconds were used to ablate the stalk and body. Temperature limits were set to protect the hypothalamus (above) and basilar artery and optic tract (below). Results: At last follow-up, continued seizure freedom was observed in all 5 patients. The average OR time was 4.1 hrs and average MR time was 1.4 hrs. No surgical complications, neurological or vision deficits, or endocrine disturbances including diabetes insipidus occurred. Conclusions: SLA was demonstrated to be a safe and effective minimally invasive tool to destroy epileptogenic HH. Seizure freedom was achieved without surgical morbidity. Short ablation times (60-120 seconds) and real-time MRI thermometry enabled protection of adjacent critical structures. Early intervention with SLA provides a precise minimally invasive tool to achieve seizure freedom in HH. Stereotactic laser procedures for minimally invasive treatment of epilepsy enables destruction of deep seated seizure foci like HH with the potential for higher rates of seizure freedom, in comparison to traditional surgeries.