Using pre-surgical suspicion to guide insula implantation strategy

• Published in: Heliyon Vol. 9; no. 7; p. e18284
• Main Authors: Cameron, Nathaniel, Fry, Lane, Kabangu, Jean-Luc, Schatmeyer, Bryan A., Miller, Christopher, Ulloa, Carol M., Uysal, Utku, Cheng, Jennifer J., Kinsman, Michael J., Rouse, Adam G., Landazuri, Patrick
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2023; Elsevier
• Subjects: Ictal-onset; Insula; Safety; sEEG; sEEG; Insula; Safety; Ictal-onset
• ISSN: 2405-8440; 2405-8440
• DOI: 10.1016/j.heliyon.2023.e18284

Insular epilepsy can be a challenging diagnosis due to overlapping semiology and scalp EEG findings with frontal, temporal, and parietal lobe epilepsies. Stereotactic electroencephalography (sEEG) provides an opportunity to better localize seizure onset. The possibility of improved localization is balanced by implantation risk in this vascularly rich anatomic region. We review both safety and pre-implantation factors involved in insular electrode placement across four years at an academic medical center. Presurgical data, operative reports, and invasive EEG summaries were retrospectively reviewed for patients undergoing invasive epilepsy monitoring on the insula from 2016 through 2019. EEG reports were reviewed to record the presence of insula ictal and interictal involvement. We recorded which presurgical findings suggested insular involvement (insula lesion on MRI, insula changes on PET/SPECT/scalp EEG, characteristic semiology, or history of failed anterior temporal lobectomy). The likelihood of pre-sEEG insular onset was categorized as low suspicion if no presurgical findings were present (“rule out”), moderate suspicion if one finding was present, and high suspicion if two or more findings were present. 76 patients received 189 insular electrodes as part of their implantation strategy for 79 surgical cases. Seven patients (8.9%) had insular ictal onset. One clinically significant complication (left hemiparesis) occurred in a patient with moderate suspicion for insular onset. There were 38 low suspicion cases, 36 moderate suspicion cases, and 5 high suspicion cases for pre-sEEG insula ictal onset. Two low suspicion (5.3%), three moderate suspicion (8.6%), and two high suspicion (40%) cases had insular ictal onset. The insula can safely receive sEEG. Having two or more presurgical factors indicating insular onset is a strong, albeit incomplete, predictor of insular seizure onset. Using pre-implantation clinical findings can offer clinicians predictive value for targeting the insula during invasive EEG monitoring. •While not risk-free, invasive epilepsy monitoring of the insula can be safely pursued when needed.•Having more than one pre-implantation finding suggestive of insula involvement is predictive of insula epilepsy.•One pre-implantation finding is predictive of insula involvement through either ictal onset or site of first spread.•Pre-surgical electroclinical and imaging data inform the diagnostic yield of insula depth electrode implantation.