T144. EEG resting states are altered in focal epilepsy

Abstract

Resting states represent the basic “atoms of thought” in the resting EEG but were found to be altered in a number of psychiatric and dementia conditions. In most studies, 4 basic maps are described (A = auditory, B = visual, C = salience, D = attention). In the present study we wanted to determine if EEG resting states are also altered in patients with chronic epilepsy 25 patients with chronic unifocal epilepsy were included. All patients underwent 37 channel EEGs. Three minutes of wake EEG without any detectable spikes were selected. We fitted the 4 EEG microstates to the: (i) EEG of patient without any visible spike and (ii) resting-state EEGs of 48 healthy-controls (HC). Global Explained Variance (GEV), Mean duration (MD) and Time Coverage (TC) were used to characterize the map amount. We found a significant GEV increase of map-D (p < 0.001), and decrease of map-C (p < 0.001). For map-C there was also a decrease of MD (p < 0.001) and TC (p < 0.01). These results did not change when fitting included the patient’s individual spike map. Physiologic resting state networks are significantly altered in patients with chronic epilepsy, which affects mainly the so-called salience (map-C) and attention states (map-D). Saliency networks include the anterior insula and dorsal anterior cingulate and play a crucial role in identifying relevant events to guide and adapt behavior. The increase of the attention map (parietal cortex, anterior cingulate, thalamus) probably reflects compensation of impaired salience functions. Further studies will determine if these changes could become an EEG biomarker of epilepsy, e.g. for patients with spike-negative EEG.