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Insular Epilepsy: Semiology and Noninvasive Investigations

Obaid, Sami*; Zerouali, Younes; Nguyen, Dang Khoa

Journal of Clinical Neurophysiology: July 2017 - Volume 34 - Issue 4 - p 315–323
doi: 10.1097/WNP.0000000000000396
Invited Review

Summary: In this review, authors discuss the semiology and noninvasive investigations of insular epilepsy, an underrecognized type of epilepsy, which may mimic other focal epilepsies. In line with the various functions of the insula and its widespread network of connections, insular epilepsy may feature a variety of early ictal manifestations from somatosensory, visceral, olfactory, gustatory, or vestibular manifestations. Depending on propagation pathways, insular seizures may also include altered consciousness, dystonic posturing, complex motor behaviors, and even autonomic features. Considering the variability in seizure semiology, recognition of insular epilepsy may be challenging and confirmation by noninvasive tests is warranted although few studies have assessed their value. Detection of an insular lesion on MRI greatly facilitates the diagnosis. Scalp EEG findings in frontocentral and/or temporal derivations will generally allow lateralization of the seizure focus. Ictal single-photon computed tomography has moderate sensitivity, whereas positron emission tomography has lower sensitivity. Among newer techniques, magnetoencephalography is highly beneficial, whereas proton magnetic resonance spectroscopy currently has limited value.

Divisions of *Neurosurgery and

Neurology, Centre Hospitalier de l'Université de Montréal (CHUM)—Hôpital Notre-Dame, Université de Montréal, Montreal, QC, Canada; and

Department of Neurosciences, Faculty of Medicine, Université de Montréal , Montreal, QC, Canada.

Address correspondence and reprint requests to Dang Khoa Nguyen, MD, PhD, CHUM—Hôpital Notre-Dame, 1560 Sherbrooke East, Montreal, QC H2L 4M1, Canada; e-mail: d.nguyen@umontreal.ca.

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

© 2017 by the American Clinical Neurophysiology Society