Abstracts

Rationale: To correlate extent of amygdala and hippocampal stereotactic laser amygdalo-hippocampotomy (SLAH) for mesial temporal lobe epileptogenic foci (MTLE). Methods: Among seven centers with institutional review board-approved protocols for investigator-initiated studies, case report forms were collected for subjects who had undergone SLAH (Visualase, Inc., Houston, Texas). MRI data collected from these subjects post-ablation was analyzed to correlate Engel I status at 12-months post-ablation with proportion of amygdala and/or hippocampus determined. Volumetric analysis was conducted using slice-by-slice outlining comparing post-ablation vs. pre-ablation volumes to determine the percentage ablation of amygdala and/or hippocampus. Results: From the seven centers submitting data for volumetric analysis post-SLAH, data for ablation volume of both the amygdala and hippocampus was available for 19 subjects at both 6-month and 12-month follow-up. Correlated to seizure freedom at 12-month follow-up, ablation of >70% of either structure (hippocampus or amygdala) and >50% of the remaining structure resulted in 80% of subjects achieving Engel I status (n=5 meeting these criteria, out of total n=19); ablation of >50% of each structure simultaneously led to 56% achieving Engel I status (n=9 meeting these criteria, out of total n=19). Overall seizure freedom in the entire group post-SLAH was 58%, so ablation of less than 50% of either structure resulted in markedly lower Engel I status achievement. Conclusions: While logically the greater the volume of both hippocampus and amygdala ablated the greater the chance of improvement from seizures, the present work establishes guidelines which can help guide the surgeon using SLAH toward optimal trajectory, and help predict likelihood of improvement. This preliminary data prompts the need for larger studies to establish and reinforce such parameters for optimal targeting of hippocampus and amygdala structures for seizure improvement in MTLE. Key words: mesial temporal lobe epileptogenic foci; stereotactic laser ablation; target; volumetric analysis; outcome; seizure freedom; stereotactic laser amygdalo-hippocampotomy