Electroencephalographic Phase Synchrony Index as a Biomarker of Post-Stroke Aphasia Recovery

BackgroundPost-stroke aphasia is considered a language network disorder, and neuroimaging may help understand network alterations. However, the prediction of aphasia recovery remains challenging.ObjectiveWe aimed to explore biomarkers for aphasia recovery using a novel clinically feasible method, which we previously reported as useful for evaluating motor recovery, that included the phase synchrony index (PSI) obtained from resting-state 19-channel electroencephalography.MethodsThis longitudinal observational study included patients with left frontal ischemic lesions admitted for post-acute rehabilitation. We recorded electroencephalograms at the time of admission. Recovery was defined as a change in composite speech score. Based on electrode settings, we focused on 4 language-related networks: (1) left front-temporal, (2) right front-temporal, (3) inter-frontal, and (4) inter-temporal networks. We first evaluated the correlation between these network PSIs and recovery scores and then the predictive potential of our method using the receiver operating characteristic curve and multivariable regression analyses.ResultsWe enrolled 24 patients. Electroencephalograms were recorded for a median of 37.0 days after the stroke. The median speech therapy time was 53.7 hours. Inter-temporal PSI (gamma band) was significantly positively correlated with recovery scores (ρ = .642; 95% confidence interval = 0.311-0.834; <i>P</i> = .017). The PSI could predict patients with good recovery (sensitivity = 84.6%; specificity = 90.9%), and the inter-temporal PSIs were useful in predicting recovery (adjusted <i>R</i>² = .545).ConclusionsOur results revealed an association between the posterior language network adaptive response and speech recovery in patients with frontal lesions. The PSI may reflect post-stroke network alterations and may be a biomarker of aphasia recovery.