Resident physician University of California-San Francisco
Rationale: A fundamental question in epilepsy surgery is how to delineate the margins of cortex that must be resected to result in seizure freedom. Whether and which areas showing seizure activity early in ictus must be removed to avoid post-operative recurrence of seizures is an area of ongoing research. While seizure spread dynamics in the initial seconds of ictus are often correlated with postoperative outcome, there is no consensus definition of early spread, nor is there a concise summary of the existing literature linking seizure spread to post-surgical seizure outcomes. The present study is intended to summarize the literature linking seizure spread to postoperative seizure outcome and provide a framework for quantitative assessment of early seizure spread. Methods: A systematic review was carried out according to PRISMA guidelines. A Medline search identified clinical studies reporting data on seizure spread measured by intracranial electrodes, having at least 10 subjects and reporting at least one-year postoperative outcome in the English literature from 1990 to 2019. Studies were evaluated regarding support for a primary hypothesis: Areas of early seizure spread represent cortex with seizure-generating potential. Results: The search yielded 4,562 studies. Fifteen studies met inclusion criteria. Seven studies supported the primary hypothesis. The methods and metrics used to describe seizure spread were heterogenous. The timeframe of seizure spread associated with seizure outcome ranged from 1 – 14 seconds, with large, well-designed, retrospective studies pointing to 3 – 10 seconds as most likely to provide meaningful correlates of postoperative seizure freedom. Conclusions: The complex correlation between electrophysiologic seizure spread and the potential for seizure generation needs further elucidation. Prospective cohort studies or trials are needed to evaluate epilepsy surgery targeting cortex involved in the first three to ten seconds of ictus. Funding: Please list any funding that was received in support of this abstract.: None
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