Objective Direct electrical stimulations of cerebral cortex are a traditional part of stereoelectroencephalography (SEEG) practice, but their value as a predictive factor for seizure outcome has never been carefully investigated.
Patients and method We retrospectively analysed a cohort of 346 patients operated on for drug-resistant focal epilepsy after SEEG exploration. As potential predictors we included: aetiology, MRI data, age of onset, duration of epilepsy, age at surgery, topography of surgery and whether a seizure was induced by either low frequency electrical stimulation (LFS) or high frequency electrical stimulation.
Results Of 346 patients, 63.6% had good outcome (no seizure recurrence, Engel I). Univariate analysis demonstrated significant correlation with favourable outcome (Engel I) for: aetiology, positive MRI and seizure induced by stimulation. At multivariate analysis, informative MRI, type II focal cortical dysplasia and tumour reduced the risk of seizure recurrence (SR) by 47%, 58% and 81%, respectively. Compared with the absence of induced seizures, the occurrence of ictal events after LFS significantly predicts a favourable outcome on seizures, with only 44% chance of disabling SR at last follow-up.
Conclusion Among the already known predictors outcome, seizure induction by LFS therefore represents a positive predictive factor for seizure outcome after surgery.
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Contributors Conception or design of the work AT and SF; data collection AT, RR, FC, SL, AM, GLR, DS, RC, RM, PC, FB, SF; data analysis and interpretation: AT, RR, FC, SL, AM, GLR, DS, RC, RM, PC, FB, SF; drafting the article: AT, FC, SL, AM, FB, SF; critical revision of the article: AT, FC, SL, AM, FB, SF; final approval of the version to be published: AT, RR, FC, SL, AM, GLR, DS, RC, RM, PC, FB, SF.
Funding This work has been carried out within the FHU EPINEXT with the support of the A*MIDEX project (ANR-11-IDEX-0001–02) funded by the 'Investissements d'Avenir' French Government programme managed by the French National Research Agency (ANR). Part of this work was funded by a joint Agence Nationale de la Recherche (ANR) and Direction Génerale de l'Offre de Santé (DGOS) under grant 'VIBRATIONS” ANR 13 PRTS 0011 01'.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The protocol for this study received approval from the Niguardia Institutional Review Board and by the institutional review board of the French Institute of Health (IRB15226).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. The deidentified participant data (Marse01, Marse02 Nig01, Nig02) are available from the corresponding author email@example.com. Both centre and department have to give the permission to reuse the database.