Abstracts

Rationale: MRI-guided thermal ablation is a relatively new stereotactic surgical technique utilizing laser induced heat for tissue ablation. Results of surgical removal of epileptiform lesions of the frontal lobe are often suboptimal. Additionally, removal of frontal lesions may cause significant morbidity risk such as language difficulties, contralateral apraxia and persistent weakness. Disrupting circuitry or traversing normal functioning cortex is often implicated as the cause functional impairment. We hypothesized that the laser ablation technique would provide good seizure control and decreased post-surgical morbidity.Methods: The epilepsy database was reviewed from June 2013 to present. Only patients in whom frontal lobe isolated or adjoining lesions, and those with at least 3 months follow-up, were included in the analysis. All patients had pre-surgical workup consistent with seizures originating from the frontal lobe. Most had depth or subdural electrode placement for confirmation. Stereotactic placement of laser applicator probes were placed in the operating room with ablation performed in an intraoperative MRI suite. The patients had neuropsychological testing prior to and 6 months post-ablation. All patients were evaluated for seizure burden according to Engel Class for surgical outcomes at the last clinical assessment. Additionally, morbidity post-ablation was assessed.Results: 30 of 122 patients with surgical procedures (excluding VNS) had laser ablations. 8 of 30 (26.67%) had a focal frontal lesion ablated. A total of 7 ablated patients had identifiable, isolated focal lesions consistent with dysplasia. Two of these patients were diagnosed with tuberous sclerosis. The other patient had pathologically diagnosed benign glioma. 2 patients had undergone prior surgical resection and 2 underwent two ablation procedures. 5 had involvement of the right frontal lobe (cingulate, inferior frontal (operculum), prefrontal, and lateral frontal) and 3 the left frontal lobe (supplementary motor area, inferior frontal gyrus, and mesial frontal/anterior insula). Depth electrodes were placed in 6 patients (subdural electrodes in one). 7 patients in this study reported Engel Class Ia outcome and one with TS class 3a outcome. One patient had contralateral foot weakness after surgery which has completely resolved. 7 patients went home one day post ablation, but one (the patient with subdural electrodes placed) remained for two days for observation. No neuropsychological sequelae were evident in tested patients to date.Conclusions: MRI-guided stereotactic thermal ablation appears to be an effective surgical option for patients with lesional frontal lobe epilepsy. Seizure outcome with complete lesion ablation revealed equivalent or better efficacy than resective surgery thus far although longer term follow-up is obviously required. Laser ablation may therefore be an effective alternative to traditional resection for treating seizures induced by frontal lesions while providing decreased risk of physical and neuropsychological deficits.