Seizure onset patterns predict outcome after stereotactic electroencephalography-guided laser amygdalohippocampotomy

Abstract Objective Stereotactic laser amygdalohippocampotomy (SLAH) is an appealing option for patients with temporal lobe epilepsy, who often require intracranial monitoring to confirm mesial temporal seizure onset. However, given limited spatial sampling, it is possible that stereotactic electroencephalography (sEEG) may miss seizure onset elsewhere. We hypothesized that sEEG seizure onset patterns (SOPs) may differentiate between primary onset and secondary spread and predict postoperative seizure control. In this study, we characterized the two-year outcomes of patients who underwent single-probe SLAH after sEEG and evaluated whether sEEG SOPs predict postoperative seizure freedom. Methods This retrospective five-center study included patients with or without mesial temporal sclerosis (MTS) who underwent sEEG followed by single probe SLAH between August 2014 and January 2022. Patients with causative hippocampal lesions apart from MTS or for whom the SLAH was considered palliative were excluded. A SOP catalogue was developed based on literature review. The dominant pattern for each patient was used for survival analysis. The primary outcome was two-year Engel I classification or recurrent seizures before then, stratified by SOP category. Results 58 patients were included with a mean follow-up duration of 39 ± 12 months after SLAH. Overall one-, two, and three-year Engel I seizure freedom probability was 54%, 36%, and 33% respectively. Patients with SOPs including low voltage fast activity or low frequency repetitive spiking had a 46% two-year seizure freedom probability, compared to 0% for patients with alpha or theta frequency repetitive spiking or theta or delta frequency rhythmic slowing (log rank test, p = 0.00015). Significance Patients who underwent SLAH after sEEG had a low probability of seizure freedom at two years, but SOPs successfully predicted seizure recurrence in a subset of patients. This study provides proof of concept that SOPs distinguish between seizure onset and spread and supports using SOPs to improve selection of SLAH candidates. Key Points We described extended seizure outcomes in a five-center retrospective review of 58 patients. Seizure onset patterns (SOP) were categorized as putative positive vs. negative predictors of postoperative seizure freedom. Low voltage fast activity or low frequency repetitive spiking are associated with higher seizure freedom probability A 0% Engel I probability was found for patients whose dominant SOP was rhythmic slowing or repetitive spiking in the theta or alpha frequency bands.