Insular cortex and epilepsy paradigm. Literature review

Abstract

Background: The insula, first described in 1786 by Felix Vicq d'Azyr, later renamed Reil's island in 1809, was described by Clark as the fifth brain lobe in 1896. Initially considered an isolated lobe, belonging to the autonomic nervous system, it later proved to have broad anatomical and functional connections with brain structures. The relevant terms’ combination [insula OR insular cortex] AND epilepsy was searched on PubMed database. The following filters were applied: publication date – 21 years, species – humans, age of subjects – 19+, language – English. Out of 170 identified results only Reviews (17), Retrospective studies (6), Case Reports (5) and Books (1) were analyzed (total – 27 papers). The insular cortex is a true anatomical hub for integration, with high connectivity to an extensive network of brain regions, and has a variety of functions. Insula has three main propagation pathways in the epileptogenic network, respectively, insular epilepsy can “imitate” other types of seizures: frontal hypermotor, temporal focal motor with oroalimentary automatisms or parietal focal somatosensory seizures. Insular seizures have a polymorphic semiology: from major symptoms, with insulo-opercular semiology-somatosensory manifestations, and pseudo-frontal semiology with hypermotor seizures, up to minor symptoms. Conclusions: Although insula has a variety of functions and it is a part of epileptogenic networks, it remains an enigma to many clinicians to this day, and seizures with insular onset can mimic other types of epileptic seizures. Currently there is a need to improve the recognition and understanding of the semiology of insular seizures.