Abstracts

Rationale: While hippocampal atrophy has been shown to be predictive of success following temporal lobectomy, its predictive value post-super selective stereotactic laser ablation (SLA) is analyzed by the present study. Methods: Among seven centers with prospective, institutional review board (IRB)-approved protocols for investigator-initiated studies using laser ablation (Visualase, Inc., Houston, Texas) for amygdala and hippocampal ablation, case report forms (CRFs), were collected. Pre-ablation MRI data collected from these subjects was analyzed to correlate seizure freedom at 6-months post-ablation, with proportion of hippocampal atrophy. Volumetric analysis was conducted using slice-by-slice outlining comparing post-pre-ablation hippocampal volumes. Results: From the seven centers submitting data for volumetric analysis post-SLAH, data for 6-month Engel I outcome were available for 23 subjects at 6-month follow-up. Collectively, this group had 59% achieve Engel I status. Among these, if >25% hippocampal atrophy were present (comparing ablated side vs. the contralateral side), 75% of subjects achieved Engel I status; conversely, those with <25% discrepancy in ablated vs. contralateral hippocampus were found to have only 37% achieving Engel I status, with a statistical trend noted (Fisher's one-tailed exact test, p=0.07). Conclusions: A 25% or greater volumetric disparity between hippocampi in the same patient was found to trend towards greater likelihood of achieving Engel I status following super-selective stereotactic laser ablation. This preliminary data prompts the need for larger studies to establish and reinforce such parameters for optimal laser targeting of hippocampus and amygdala structures for seizure freedom in MTLE