Laser Ablation of Periventricular Nodular Heterotopia for Medically Refractory Epilepsy

Objective: Periventricular Nodular Heterotopia (PVNH) is the most common neuronal heterotopia, frequently resulting in pharmacoresistant epilepsy. PVNH has a deep location which renders localization of seizure onsets and traditional surgical therapy challenging and of limited success. Here we characterize variables that predict good epilepsy outcomes following surgical intervention using SEEG informed MRgLITT. Methods: A prospectively compiled surgical epilepsy database from a single high-volume epilepsy referral center was used to identify patients who underwent SEEG evaluation for PVNH and characterize the intervention on outcomes. Results: Thirty-nine patients underwent SEEG informed MRgLITT. Associated imaging abnormalities mesial temporal sclerosis (MTS) or polymicrogyria (PMG) were treated based on SEEG. SEEG guided MRgLITT of the seizure onset zone (SoZ) in PVNH and associated epileptic tissue was carried out. PVNH and PMG were densely sampled mean 16.5(SD=2)/209.4(SD=36.9) SEEG probes/recording contacts. A single trajectory was used in 18, two in 13, and three or more in eight patients. Volumetric analyses revealed a high percentage of PVNH SoZ ablation (96.6%, SD=5.3%) in unilateral and bilateral (92.9%, SD=7.2%) cases. Mean follow-up duration was 31.4 months (SD=20.9). Seizure freedom was excellent overall: unilateral PVNH without other imaging abnormalities 80%; PVNH with MTS or PMG 63%; Bilateral PVNH 50%. SoZ ablation percentage significantly impacted surgical outcomes (p<0.001). Interpretation: PVNH plays a central role in seizure genesis. MRgLITT represents a transformative technological advance in PVNH associated epilepsy with seizure control outcomes consistent with those seen in focal lesional epilepsies. In localized unilateral cases and otherwise normal imaging, performing PVNH ablation without invasive recordings may be reasonable.