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Operculo-Insular Epilepsy: Scalp and Intracranial Electroencephalographic Findings

Levy, Ariel*; Yen Tran, Thi Phuoc*,†; Boucher, Olivier; Bouthillier, Alain§; Nguyen, Dang Khoa*

Journal of Clinical Neurophysiology: September 2017 - Volume 34 - Issue 5 - p 438–447
doi: 10.1097/WNP.0000000000000391
Original Research

Purpose: Operculo-insular seizures are heterogeneous and may resemble seizures originating from the temporal, frontal, or parietal lobe. Although surface and invasive EEG recordings are often necessary to detect operculo-insular seizures, electrophysiological features of operculo-insular epilepsies remain poorly characterized. This study describes the EEG findings of patients with operculo-insular epilepsy.

Methods: We reviewed electrophysiological data of all patients (n = 9) with operculo-insular seizures revealed by intracranial EEG and for whom operculo-insular epilepsy was confirmed by good seizure outcome after resective or radiosurgery at our center between 2005 and 2013. Patients were divided according to whether their seizure focus involved the anterior (group 1; n = 4) or posterior (group 2; n = 5) portion of the insula.

Results: Interictal scalp EEG was lateralizing and showed distinct topographical spike patterns between groups: frontal and temporal in group 1, temporal in group 2. Intracranial recordings showed abundant spikes limited to the operculo-insular region or involving distant areas in the frontal/temporal (group 1) and temporal/parietal lobes (group 2). Ictal intracranial EEG revealed discharges limited to the insula or simultaneously involving extrainsular contacts at onset, notably the orbitofrontal cortex (group 1) and the frontal and parietal opercula (group 2), and propagating to the frontal and temporal lobes in group 1 and to parietal and temporal lobes in group 2.

Conclusions: Spike distribution and seizure propagation in operculo-insular epilepsy follows an anterior-to-posterior pattern mirroring an anterior or posterior insular focus localization. When presented with frontal and/or temporal epileptiform abnormalities, an operculo-insular focus should be considered.

Supplemental Digital Content is Available in the Text.

*Division of Neurology, CHUM Notre-Dame, Université de Montréal, Montréal, QC, Canada;

Department of Internal Medicine, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam;

Département de psychologie, Université de Montréal, Montréal, QC, Canada; and

§Division of Neurosurgery, CHUM Notre-Dame, Université de Montréal, Montréal, QC, Canada.

Address correspondence and reprint requests to Dang Khoa Nguyen, MD, PhD, CHUM Notre-Dame, 1560 Sherbrooke East, Montréal, QC H2L 4M1, Canada; e-mail:

The authors have no funding or conflicts of interest to disclose.

Presented at the Annual Meeting of the American Clinical Neurophysiology Society, Orlando, FL, February 14, 2016.

A. Levy and T. P. Yen Tran contributed equally to this work.

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© 2017 by the American Clinical Neurophysiology Society