Differentiation with electroencephalography microstate in temporal lobe epilepsy with and without cognitive decline

Electroencephalography (EEG) microstate analysis is widely used in the study of various neurological and psychiatric disorders. We aim to assess whether EEG microstates are altered in TLE patients with and without cognitive decline.

This study included a total of 47 temporal lobe epilepsy (TLE) patients with or without cognitive decline and 14 healthy controls (HCs). All participants underwent 64-channel EEG monitoring. Two-minute epochs of preprocessed eye closed awake EEG data were extracted for microstate analysis. Participants were divided into groups based on intelligence quotient (IQ) scores assessed by the Wechsler Intelligence Scale: normal cognition group (n = 23, IQ ≥ 90) and abnormal cognition group (n = 24, IQ < 90). We conducted frequency spectral analysis on each frequency sub-bands (delta, 1-4 Hz; theta, 4-8 Hz; alpha, 8-12 Hz; beta, 12-30 Hz) of the three groups. Then the following microstate parameters were extracted for analysis over the full frequency band (1-30 Hz) and frequency sub-bands: duration, coverage, occurrence, and transition probability. Statistical analysis using multivariate analysis of variance (MANOVA) with Bonferroni correction (α = 0.0025).

Microstate analysis in the beta sub-band revealed significant differences among groups. TLE patients with abnormal cognition showed increased occurrence of Map-D; significantly higher transition probabilities from Map-A, Map-B, and Map-C to Map-D; and distinct microstate characteristics compared to patients with normal cognition and HCs. In frequency spectral analysis, the power across all frequency sub-bands showed no significant differences among TLE patients with normal cognition, TLE patients with abnormal cognition, and HCs.

Beta sub-band EEG microstates, particularly Map-D characteristics, may serve as potential neurophysiological markers for cognitive decline in TLE patients.