Abstracts

Rationale: Stereotactic magnetic resonance imaging-guided laser amygdalohippocampotomy (SLAH) may offer an attractive, less invasive alternative to standard open surgeries, specifically anterior temporal lobectomy amygdalohippocampectomy (ATLAH) and selective amygdalohippocampectomy (SAH), for the treatment of pharmaco-resistant mesial temporal lobe epilepsy (MTLE). A few small, published series have demonstrated promising short term seizure results (Neurosurgery 2014; 74(6); 569-584, Epilepsia 2016; 57(2); 325-334), while also sparing patients the neurocognitive deficits typically associated with open resections (Epilepsia 2013; 54(suppl. 3); 20, Epilepsia 2015; 56(1); 101-113). 12-month seizure outcomes of SLAH are less well established when compared to ATLAH and SAH. A recent meta-analysis comparing ATLAH and SAH for treatment of MTLE showed 12-month seizure freedom rates of 75% and 67%, respectively, with the subset of patients with mesial temporal sclerosis (MTS) experiencing higher rates of 78% and 71%, respectively (Neurology 2013; 80(18); 1669-1676). Here we present the 12-month epilepsy outcomes for MTLE patients that underwent SLAH at a single center. Methods: All 42 MTLE patients (26 with MTS) that underwent SLAH with follow-up of ?-12 months are included. Surgical outcome was stratified by Engel's classification scheme. Results were retrospectively analyzed as a noninferiority trial, with the objective performance criterion (OPC) set at 67%, equivalent to the SAH seizure freedom rate, and the noninferiority margin (f) set at 8%, the absolute risk reduction between ATLAH and SAH seizure freedom rates. The subgroup of patients with MTS and without dual pathology or prior seizure surgery were similarly analyzed (OPC=71%, f=7%). Results: 47.6% (95% CI 15.8%) of all MTLE patients, and 53.8% (95% CI 20.5%) of MTS patients without dual pathology or prior resection, who received SLAH were seizure free for ?-12 months. Five of 9 patients then became seizure free for ?-12 months following repeat ablation yielding total 57.1% (95% CI 15.7%) of all MTLE patients and 61.5% (95% CI 20.0%) of MTS patients seizure free for ?-12 months. This demonstrates the statistical noninferiority of SLAH to SAH. There were 2 postoperative visual field deficits and 2 hemorrhages, both without persistent deficit, and 1 cranial nerve palsy. Conclusions: Expanding our previous series, we report the largest single center experience to date, showing that SLAH is statistically noninferior to SAH with respect to seizure freedom at 12 months. Consistent with open temporal lobe surgery there was greater likelihood of seizure freedom in patients with MTS (without dual pathology or previous resection). Five patients became seizure free after repeat ablation suggesting technical failure in the first procedure. Our results support SLAH as a viable, minimally invasive, noninferior alternative to open temporal lobe surgery in patients with MTLE. Funding: Medtronic Inc. (formally, Visualase Inc.)