Electrocorticographic Patterns in Epilepsy Surgery and Long-Term Outcome
Daniel San-Juan1, Mario Arturo Alonso-Vanegas, Carlos Trenado
1Departments of *Clinical Neurophysiology and †Neurosurgery, National Institute of Neurology and Neurosurgery, Mexico City, Mexico; ‡Centre for Movement Disorders and Neuromodulation Institute of Clinical Neuroscience and Medical Psychology, University Hospital Düsseldorf, Düsseldorf, Germany; §Department Clinical Neurophysiology, "November 20" Medical Center, Institute for Social Security and Services for State Workers, Mexico City, Mexico; ‖Medicine Academic Unit, Autonomous University of Nayarit, Tepic, Mexico; and ¶Clinical Research Department, Superior School of Medicine, National Polytechnic Institute, Mexico City, Mexico.
Purpose:
The role of intraoperative electrocorticography (iECoG) and of its patterns in epilepsy surgery have shown contradictory results. Our aim was to describe iECoG patterns and their association with outcome in epilepsy surgery.
Methods:
We retrospectively analyzed 104 patients who underwent epilepsy surgery (2009-2015) with pre- and postresection iECoG. We described clinical findings, type of surgery, preresection iECoG patterns according to Palmini et al., 1995 (sporadic, continuous, burst, and recruiting interictal epileptiform discharges-IEDs) and postresection iECoG outcome (de novo, residual, and without IEDs). The Engel scale was used to evaluate the outcome. Descriptive statistics, Kaplan-Meier, the logistic regression model, and analysis of variance tests were used.
Results:
We included 60.6% (63/104) females, with a mean age of 35 (±10.2) years at the time of epilepsy surgery. The etiologies were hippocampal sclerosis (63.5%), cavernomas (14.4%), cortical dysplasia (11.5%), and low-grade tumors (10.6%). The most common preresection iECoG pattern was sporadic IEDs (47%). Postresection iECoG patterns were de novo (55.7%), residual (27.8%), and without IEDs (16.3%). Mean follow-up was 19.2 months. Engel scale was as follows: Engel I (91 patients, 87.5%), Engel II (10 patients, 9.6%), and Engel III (three patients, 2.9%). Analysis by mixed-design analysis of variance showed a significant difference between etiology groups with a strong size effect (P = 0.021, η = 0.513) and also between preresection iECoG patterns (P = 0.008, η = 0.661).
Conclusions:
Preresection iECoG patterns and etiology influence Engel scale outcome in lesional epilepsy surgery.
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