Introduction: Traditional surgical treatment provided seizure-free outcome in ~ 58 % of patients in the only randomized surgical trial for medically refractory temporal lobe epilepsy (TLE) patients (Wiebe 2001), but vastly underutilzed. An exciting alternative is stereotactic laser ablation (SLA) that is minimally invasive. But, it is crucial to understand the ablation volume of the hippocampus and amygdala that needs to achieved to achieve seizure freedom.

Methods: 13 medically-refractory patients (6mo - 2yr follow-up) with symptomatic localization-related TLE, underwent stereotactic frame-based placement of MR-compatible laser catheter (1.6mm diameter) through a 3.2mm twist drill hole. An FDA-cleared laser surgery system (Visualase; Visualase, Inc., Houston, TX) was utilized to monitor the ablation of epileptogenic foci with real-time MRI thermometry. Anatomical structures were manually segmented on pre-procedure volumetric data sets. Post-ablation volumes were generated by manually segmented the ring enhanced ablation zone on a post-procedure T1 images. The two data sets were co-registered and percentage of amount of each structure ablated was calculated.

Results: 11/13 patients had seizure reduction. 7(54% ) out of the 13 patients achieved seizure freedom, 4(31%) had 75% or more seizure reduction and 2 patients had no change. The average percentage of ablated hippocampus and amygdala was about 60% and 45%, respectively. The percentage of amygdala ablated in seizure free group and non-seizure free group was 58% and 30%, respectively. 5/7 pts in seizure free group had smaller hippocampal volumes on ablated side. Two patients in non-seizure free group had bilateral foci and approach in another patient was inferior.

Conclusions: Seizure outcomes with SLA are comparable to the conventional surgical techniques. This volumetric analysis indicates relationship to atrophic hippocampi, >50% ablation of the amygdala and unilateral foci. More cases need to be analyzed to be indicative for seizure outcomes.

Patient Care: A better understanding of the efficacy of SLA will allow us to better define its role in the treatment of MTLE.

Learning Objectives: By the conclusion of his session, participants should be able to: 1) Acknowledge the potential of stereotactic laser ablation as a minimally-invasive alternative treatment for mesial temporal lobe epilepsy 2) Discuss the implications of preliminary findings regarding the association between volumes of ablated mesial temporal structures and seizure control

References: Samuel Wiebe, M.D., Warren T. Blume, M.D., John P. Girvin, M.D., Ph.D., and Michael Eliasziw, Ph.D. A Randomized, Controlled Trial of Surgery for Temporal-Lobe Epilepsy. N Engl J Med 2001; 345:311-318.