Bilateral insular functional connectivity in epilepsy patients: A cortico-cortical evoked potential study

Abstract

Objective To explore bilateral insular functional connectivity in refractory epilepsy patients using electrical cortical stimulation by stereoelectroencephalography (SEEG) electrodes. Methods We retrospectively analyzed the clinical data of 4 patients with insular or insular-related drug resistant epilepsy at Epilepsy Center of Yuquan Hospital of Tsinghua University from January 2014 to August 2016. Four patients were implanted with SEEG electrodes in bilateral insular lobes for cortical electrical stimulation. The evoked potential response of each contact was determined by visual analysis and nonparametric test. The evoked potential response was recorded at the contralateral insular lobe electrode on the stimulating side, and the response rate and anatomical distribution were determined. Results A total of 28 SEEG electrodes (98 contacts) were implanted into the insular lobe in 4 patients, of which 12 electrodes (47 contacts) were implanted into the left insular lobe. Cortical-cortical evoked potential (CCEP) responses were found between bilateral insular lobes in 4 patients, and homotopic bidirectional CCEP connections were found between bilateral insular lobes. The response rate of contralateral insular CCEP was 39.8%, and the peak latency was 15.5-196.0 ms. There were bi-directional CCEP connections between corresponding bilateral insular gyri. Conclusions There are bi-directional functional connections between bilateral insular lobes in patients with insular or insular-related epilepsy, particularly in patients with post-viral encephalitis epilepsy. However, more studies are needed to confirm this result. Key words: Epilepsy; Insular; Stereoelectroencephalography; Electrical cortical stimulation; Cortico-cortical evoked potential