Abstracts

Rationale: Hypothalamic Hamartoma is a rare but disabling epileptic syndrome that imparts severe refractory gelastic seizures, frequently presenting with epileptic encephalopathy. Surgery to cure gelastic seizures has traditionally been open and highly morbid. Recently minimally invasive techniques have designed to decrease operative morbidity. We present the safety profile of the multi-center experience of the use of MR-Guided Stereotactic Laser Thermoablation (SLA) in the treatment of hypothalamic hamartoma. Methods: 23 pediatric patients from five epilepsy centers presented with intractable epilepsy associated with hypothalamic hamartoma. An IRB approved protocol was for pediatric patients (2-18 y.o.) with medically intractable, focal, lesional epilepsy. An FDA-cleared surgical laser ablation system (Visualase Thermal Therapy System; Visualase, Inc., Houston, TX) was employed in this work. The cooled laser applicator is MR-compatible (1.6mm in diameter) with a central 400- m core silica fiberoptic applicator with 1 cm and 3 mm light-diffusing tips. Framed and frameless stereotaxy was used to navigate the laser applicator to the targeted foci. Magnetic resonance temperature imaging (MRTI) was used to test dose at 3-4W for 15-45 seconds to confirm applicator position, doses of 5-8W for 45-120 seconds were used to ablate the foci. Safety limits (50 C) were placed near the margin of the desired thermal ablation zone to protect critical structures like the optic tract, fornix and mammalothalamic tract. After completion of the ablation procedure, post ablation T1-weighted plus gadolinium contrast (T1 + Gd) and DWI series were acquired. Follow-up period was from 1-32monthsResults: Seizure freedom was obtained in 81% of the patients. Of the ten patients that are more than one year post-ablation, 9 are seizure free. In the 13 patients with < 1 year follow-up, 10 achieved seizure freedom and 3 had seizure reduction. Three patients achieved seizure freedom after 2nd procedure No permanent surgical complications (DI, memory impairment, hormonal changes, hemiparesis, visual changes) were noted. One patient has transient short-term memory loss, hyperthermia and hyperphagia prior to the institution of pre-ablation high does steroids. There was a single incident of sub-clinical subarachnoid hemorrhage; there were two episodes of transient hemiparesis, and three episodes of transient short-term memory deficit. There were three target inaccuracies, one with a rigid frame, two with a frameless system. There was one subgaleal CSF collection. Average LOS was 2.15 days.Conclusions: MR-Guided SLA for Hypothalamic Hamartomas appears to be a safe and effective alternative to open surgical resection in children with intractable epilepsy. Real-time, feedback-controlled ablation within the MR scanner, along with the minimally invasive approach, likely contributed to the low morbidity.