Abstracts

Rationale: Treatment resistant epilepsy is common in children and leads to substantial morbidity. For select patients, surgical techniques can be highly effective. In controlled trials, epilepsy surgery has been shown to be superior to medical therapy with seizure freedom rates of 70 - 80%. Despite this success, surgery for epilepsy is underutilized in the United States with only 1,500 cases performed yearly. This may in part be due to concerns regarding the invasiveness and morbidity associated with traditional surgical techniques. Stereotactic laser ablation (SLA) is a minimally invasive alternative for select surgical candidates. This report reviews the safety and clinical outcomes following SLA of 23 patients at a single children s hospital.Methods: This study was approved by the Baylor College of Medicine IRB and all patients were seen in the Comprehensive Epilepsy Program at Texas Children s Hospital, Houston, TX. The patients were considered candidates for traditional resective epilepsy surgery and were offered SLA as an alternative. Epileptic foci had varied etiologies: 14 hypothalamic hamartomas, 4 focal cortical dysplasia, 3 hippocampal sclerosis, 1 developmental tumor, and 1 tuberous sclerosis complex. An FDA-cleared surgical laser ablation system (Visualase Thermal Therapy System; Visualase, Inc., Houston, TX) was employed. The cooled laser applicator is MR-compatible (1.6mm in diameter) with a central 400- m core silica fiberoptic applicator with a 1 cm light-diffusing tip. An MR-compatible head frame was used for stereotactic navigation. Magnetic resonance temperature imaging (MRTI) was accomplished using a fast field echo (FFE) sequence field of view. After a test dose of 3-4 watts for 15-45 seconds to confirm applicator position, doses of 5-12 watts for 45-120 seconds were used to ablate the foci. Safety limits were placed near the margin of the desired thermal ablation zone to protect critical structures. After completion of the ablation procedure, post-ablation T1-weighted plus gadolinium contrast MRI series were acquired. Follow-up period was from 13-35 months.Results: In 9 patients with 1 year or more follow-up, 7 or 9 are seizure-free (Engel 1) with one patient having had 2 separate ablations. In the 14 patients with less than 1 year follow-up, 11 are seizure-free with one patient having had 2 separate ablations. Of the remaining 3 patients, 2 had a 50% seizure reduction and 1 had no change. There were no surgical complications other than a single asymptomatic minor subarachnoid hemorrhage. Average hospital length of stay was 1 day.Conclusions: Stereotactic laser ablation of epileptic foci in children is possible and this early experience suggests robust efficacy and safety for a number of different lesions. In appropriate patients, the minimally invasive approach, high degree of precision and brief hospital stay makes SLA an attractive alternative to craniotomy. More importantly, SLA may increase the acceptance of a surgical treatment for epilepsy to patients and their families thereby reducing the enormous treatment gap that currently exists.