Abstracts

Rationale: MRI-guided thermal ablation is a minimally-invasive stereotactic surgical technique utilizing laser-induced heat to ablate epileptogenic foci. Experience has been largely restricted to lesional epilepsy with limited data on morbidity and seizure outcome following laser ablation in MRI-negative cases. Favorable outcome following surgical treatment of MRI-negative epilepsy relies on accurate localization using seizure semiology, functional neuroimaging and invasive EEG findings and can require large resections of cortical areas for best results, increasing risk of morbidity. Avoiding injury to normal tissue/circuits, the minimally-invasive nature of the procedure, and the controlled approach of viewing the ablation in real time, provides thermal ablation the potential to revolutionize the approach to managing MRI-negative epilepsy in appropriately selected candidates. In an ongoing collaboration between two pediatric epilepsy centers with extensive experience in thermal ablation, patients with MRI-negative intractable localization-related epilepsy treated with MRI-guided thermal ablation were reviewed with primary measures being seizure outcome and morbidity post ablation. Methods: The data of children with MRI-negative epilepsy who underwent laser ablation were placed in a shared Red Cap Database. Patients with palliative ablations were excluded. Duration of epilepsy; number of AEDs prior to ablation; investigative studies identifying foci and function; prior epilepsy surgeries; number of laser fibers used; duration of hospital stay; seizure outcome and acute and chronic morbidity were all addressed. Results: Eleven patients with MRI-negative intractable epilepsy were treated with laser ablation. All had presurgical epilepsy protocol MRI using 1.5T or 3T magnet strength. Average age was 5.7 years at seizure onset and 12.9 years at surgery. Seizure duration prior to ablation ranged from 2-15 years. fMRI, MEG dipole analysis, and SPECT were performed in 4, 10, and 6 patients, respectively. Eight of 11 (73%) underwent invasive EEG monitoring utilizing stereo-EEG. Two patients had gross complete lesional resections and were consequently non-lesional on followup MRI but continued to have seizures prior to ablation. Regions ablated included insular, temporal, and frontal cortex. Average fibers used was 1.8 (1-3). Mean follow up was 4.5 months (0-17) and 9/11 (82%) were seizure free or had rare seizures (Engel 1 or 2). No patients had long-term morbidity. Conclusions: MRI-guided thermal ablation is a novel surgical approach to treatment of MRI-negative intractable epilepsy with minimum morbidity. In appropriately selected candidates for which seizure onset can be accurately localized through presurgical evaluation, this technique offers a dramatic reduction in invasiveness and can provide outcomes comparable to ablation in lesional epilepsy. Our early outcome data also suggests outcome is similar to MRI-negative patients treated with open resection. Further follow up and larger cohorts are needed to substantiate these findings. Funding: none