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Original Investigation
June 10, 2019

Association of Cortical Stimulation–Induced Seizure With Surgical Outcome in Patients With Focal Drug-Resistant Epilepsy

Author Affiliations
  • 1Montreal Neurological Institute and Hospital, McGill University, Montréal, Quebec, Canada
  • 2Department of Neurology, Grenoble-Alpes University Hospital, Grenoble-Alpes University, Grenoble, France
  • 3Department of Neurosurgery, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
JAMA Neurol. Published online June 10, 2019. doi:10.1001/jamaneurol.2019.1464
Key Points

Question  Is seizure induction by cortical stimulation during intracranial electroencephalography associated with good surgical outcome in patients with focal drug-resistant epilepsy?

Findings  In this cohort study of 103 patients with focal drug-resistant epilepsy, cortical stimulation induced typical electroclinical seizures in 59 patients (57.3%). Induction of seizures was associated with better surgical outcome; a higher percentage of resected contacts from the seizure-onset zone informed by cortical stimulation, similar to that of spontaneous seizures, was associated with better surgical outcome.

Meaning  Cortical stimulation appears to be reliable in identifying the cortical area responsible for seizure generation and to be associated with surgical outcome.

Abstract

Importance  Cortical stimulation is used during presurgical epilepsy evaluation for functional mapping and for defining the cortical area responsible for seizure generation. Despite wide use of cortical stimulation, the association between cortical stimulation–induced seizures and surgical outcome remains unknown.

Objective  To assess whether removal of the seizure-onset zone resulting from cortical stimulation is associated with a good surgical outcome.

Design, Setting, and Participants  This cohort study used data from 2 tertiary epilepsy centers: Montreal Neurological Institute in Montreal, Quebec, Canada, and Grenoble-Alpes University Hospital in Grenoble, France. Participants included consecutive patients (n = 103) with focal drug-resistant epilepsy who underwent stereoelectroencephalography between January 1, 2007, and January 1, 2017. Participant selection criteria were cortical stimulation during implantation, subsequent open surgical procedure with a follow-up of 1 or more years, and complete neuroimaging data sets for superimposition between intracranial electrodes and the resection.

Main Outcomes and Measures  Cortical stimulation–induced typical electroclinical seizures, the volume of the surgical resection, and the percentage of resected electrode contacts inducing a seizure or encompassing the cortical stimulation–informed and spontaneous seizure-onset zones were identified. These measures were correlated with good (Engel class I) and poor (Engel classes II-IV) surgical outcomes. Electroclinical characteristics associated with cortical stimulation–induced seizures were analyzed.

Results  In total, 103 patients were included, of whom 54 (52.4%) were female, and the mean (SD) age was 31 (11) years. Fifty-nine patients (57.3%) had cortical stimulation–induced seizures. The percentage of patients with cortical stimulation–induced electroclinical seizures was higher in the good outcome group than in the poor outcome group (31 of 44 [70.5%] vs 28 of 59 [47.5%]; P = .02). The percentage of the resected contacts encompassing the cortical stimulation–informed seizure-onset zone correlated with surgical outcome (median [range] percentage in good vs poor outcome: 63.2% [0%-100%] vs 33.3% [0%-84.6%]; Spearman ρ = 0.38; P = .003). A similar result was observed for spontaneous seizures (median [range] percentage in good vs poor outcome: 57.1% [0%-100%] vs 32.7% [0%-100%]; Spearman ρ = 0.32; P = .002). Longer elapsed time since the most recent seizure was associated with a higher likelihood of inducing seizures (>24 hours: 64.7% vs <24 hours: 27.3%; P = .04).

Conclusions and Relevance  Seizure induction by cortical stimulation appears to identify the epileptic generator as reliably as spontaneous seizures do; this finding might lead to a more time-efficient intracranial presurgical investigation of focal epilepsy as the need to record spontaneous seizures is reduced.

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