Abstracts

Rationale: For patients with mesial temporal lobe epilepsy (MTLE), mesial temporal resection is an established and effective procedure with 12 month seizure free rates of 64% (non intent-to-treat analysis) in a prospective randomized trial (N Engl J Med 2001;345:311-8) and ~75% in a recent meta-analysis (Neurology 2013;80:1669-76). However, less invasive procedures may achieve comparable effectiveness while minimizing surgical adverse effects and may be better tolerated. Here we report Engel classification outcomes at 12 months in a consecutive series of 31 patients who underwent stereotactic laser ablation of the amygdala and hippocampus (SLAH) using laser interstitial thermal therapy (LITT).Methods: Patients who underwent standard diagnostic epilepsy surgery work-up and were determined in comprehensive surgery conference to be candidates for mesial temporal lobe resection were offered standard resection or SLAH. Seven patients underwent invasive EEG monitoring (iEEG) with depth, strip and/or foramen ovale electrodes to determine seizure onset zones that arose from mesial temporal structures. Thirty-one patients opted for SLAH and were enrolled in a prospective observational IRB-approved protocol to follow epilepsy and neuropsychological outcomes and MR imaging. SLAH was performed using MR thermographic imaging after stereotactic insertion of a laser fiber assembly via an occipital approach. Engel outcome was determined at 12 months.Results: Mesial temporal sclerosis (MTS) was present (as per 2 neuroradiologists) in 20 (MTS+) and not present in 11 (MTS-) patients. Overall 55% (17/31) patients were free of disabling seizures (Engel 1) at 12 months following SLAH, and 1 experienced rare seizures (3%). In MTS+ patients 70% (14/20) and 5% (1/20) were Engel 1 or 2, respectively, whereas 27.3% (3/11) of MTS- patients were Engel 1. Repeat SLAH was performed in 6 patients: 2 became seizure-free for ≥12 months (1 MTS+, 1 MTS-); 2 had no benefit (1 MTS+, 1 MTS-); and follow-up is too short in 2. Thus a total of 19 (61%) ultimately became seizure free: 15 (75%) with MTS, and 4 (36%) without. Six of 7 (85.7%) patients that underwent iEEG prior to SLAH became seizure free: 3 of 3 MTS+ and 3 of 4 MTS- patients. Thus, 3 of 4 MTS- patients that ultimately became seizure free first had iEEG. Three patients, all MTS-, underwent subsequent anterior temporal lobectomy, only one of whom became seizure free.Conclusions: SLAH is a well-tolerated minimally-invasive alternative to open temporal resection, with comparable seizure-free rates in patients with MTS. Combined with our prior results (Drane et al., Epilepsia 2015;56:101-13) showing improved neurocognitive impact compared to open resection, these results suggest that SLAH may become the first line procedure for patients with MTLE. It appears less effective for patients without MTS, as is the case with open resection. However, prior iEEG positively identifying the hippocampus as the onset zone seems to predict better outcome in both MTS- and MTS+ patients . Impacts on healthcare delivery remain to be determined.