Unveiling Hidden Executive Dysfunction by EEG Microstates and Functional Connectivity in Newly Diagnosed, Drug-Naïve Temporal Lobe Epilepsy

Objectives This study aimed to investigate the resting-state EEG microstate dynamics and functional connectivity in newly diagnosed temporal lobe epilepsy (TLE) patients, exploring whether these patients exhibit brain network impairment. Methods This is a retrospective case-control study. Seventeen newly diagnosed TLE patients and 16 age- and gender-matched non-epileptic controls were selected from 514 inpatients for long-term EEG during the period of 2020.1-2023.2 in Zhongshan Hospital Xiamen Branch, Xiamen, China. Resting-state EEG data epochs extracted from long-term EEG monitoring were preprocessed and analyzed for microstates using the MICROSTATELAB toolbox in EEGLAB. Functional connectivity was measured and presented by Coherence (COH), Phase-Locking value (PLV), and Phase Lag Index/weighted Phase Lag Index (PLI/wPLI). Results For microstate analysis, microstate D representing executive Control networks in TLE patients had a significantly longer mean duration, higher time coverage, and different GEV values compared to non-epileptic controls. The transition probability from microstate C representing self-referential processing to D was higher in TLE patients. In terms of functional connectivity, TLE patients showed lower PLI and wPLI in the gamma band representing cognitive function and higher values in the theta band representing epileptic network connectivity compared to controls. Conclusion Our findings demonstrate that executive dysfunction emerges at the earliest stage of temporal lobe epilepsy, prior to medication, as detected by EEG microstate and functional connectivity analyses. These results suggest novel electrophysiological markers for subclinical cognitive impairment and underscore the need for early monitoring and tailored interventions.