Laser Ablation of Periventricular Nodular Heterotopia for Medically Refractory Epilepsy

Objective Periventricular Nodular Heterotopia (PVNH) is the most common neuronal heterotopia, frequently resulting in pharmaco-resistant 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Committee for the Protection of Human Subjects (CPHS) of the University of Texas Health Science Center at Houston gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript * PVNH : Periventricular Nodular Heterotopia SEEG : Stereoelectroencephalography MRgLITT : Magnetic Resonance-Guided Laser Interstitial Thermal Therapy MTS : Mesial Temporal Sclerosis PMG : Polymicrogyria SoZ : Seizure Onset Zone ASM : Antiseizure Medication FDG-PET : 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography MEG : magnetoencephalography ATL : Anterior Temporal Lobectomy VNS : Vagal Nerve Stimulator FTBTC : Focal to bilateral tonic-clonic FIAS : focal impaired awareness seizures SDE : Subdural Grid Electrode SAH : Selective Amygdalohippocampectomy FCD : Focal Cortical Dysplasia HS : Hippocampal Sclerosis RNS : Responsive Neurostimulation VNS : Vagal Nerve Stimulator