Abstracts

Rationale: Approximately, 3 million people in the United Stated have epilepsy and it is estimated that at least one-third of them continue to have seizures despite adequate treatment with anti-seizure medication. An estimated 2500 pediatric patients are eligible for epilepsy surgery yearly in the United States. Surgery is vastly underutilized, about 15%, due to its invasiveness and morbidity. Stereotactic laser ablation (SLA) for localized epileptic foci is an exciting alternative for surgical candidates and here, we will discuss the safety and one year post-operative seizure outcomes after SLA(n=23). Methods: All patients (n=23) were considered candidates for resective epilepsy surgery by the hospital Comprehensive Epilepsy Surgery Conference. The IRB approved protocol was for pediatric patients ( 2-18 y.o.) with medically intractable, focal, lesional epilepsy. Epileptic foci had varied etiologies (HH: 14, FCDs: 5, MTS: 3, TS: 1). 6 patients underwent repeat procedures. 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-μm core silica fiberoptic applicator with 1 cm or 3 mm light-diffusing tips. An MR-compatible head frame was used to navigate the laser applicator to the targeted focus. Magnetic resonance temperature imaging (MRTI) was accomplished using a fast field echo (FFE) sequence (single or multiple slices) field of view: 24 cm; acquisition matrix: 256 by 128; echo time: 20 ms; repetition time: 45 ms; flip angle: 30 degrees; band width: 12.6 kHz). After a test dose of 3-4W for 15-45 seconds to confirm applicator position, doses of 5-12W for 45-120 seconds were used to ablate the focus. Safety limits (> 50⁰C ) 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) series were acquired. Follow-up period was > 1 year for all patients. Results: 65 % of all patients had seizure freedom. 93% of the HH pts were seizure free and 60 % of the FCD pts were seizure free. No surgical complications were noted. 3 had short term memory loss which resolved. There was a single incident of sub-clinical subarachnoid hemorrhage, which required no intervention. Average LOS was 1 day. Conclusions: In the current study, stereotactic laser ablation (SLA) for epileptic foci has demonstrated rates of seizure freedom that to open surgical results, especially as seen in the HH patients. Excellent outcomes with low morbidity reduced LOS and ability to stage procedures, offers a real option for the large treatment-resistant pediatric patient population.