EEG functional connectivity measures for differentiating 6-month consciousness-related outcome after brain injury

Prognostication in patients with impaired consciousness after brain injury remains challenging because clinical assessments such as the Glasgow Coma Scale (GCS) may not fully capture underlying neurophysiological function. Electroencephalography (EEG) provides an accessible approach for assessing functional brain connectivity at the bedside. This study explored the association between EEG connectivity, clinical variables, and 6-month consciousness-related outcomes after brain injury.

EEG was recorded from 111 hospitalized patients with impaired consciousness after brain injury. Baseline clinical status was assessed using the GCS. Patients were followed for 6 months and categorized according to command-following ability into good outcome and bad outcome groups. Functional connectivity was computed using weighted phase lag index (wPLI), debiased squared wPLI (wPLI²), and coherence. Clinical and EEG variables were evaluated using group comparisons, multivariable regression, receiver operating characteristic analysis, leave-one-out cross-validation, and sensitivity analyses.

Patients in the good outcome group were younger and had higher baseline GCS scores than those in the bad outcome group. Among EEG measures, alpha-band wPLI during the moving condition showed the strongest nominal group difference, with higher values in the good outcome group (nominal p = 0.006). This result did not survive false discovery rate correction across EEG connectivity variables (pFDR = 0.169). Alpha-band wPLI showed a nominal adjusted association with the 6-month consciousness-related outcome after adjustment for age and GCS, although the estimate was imprecise and attenuated in sensitivity analyses. In leave-one-out cross-validation, the clinical single-modality analysis using age and GCS achieved an AUC of 0.778, whereas the multimodality analysis combining age, GCS, and mean wPLI achieved an AUC of 0.733. The incremental improvement from adding EEG connectivity to clinical variables was not statistically significant.

Alpha-band wPLI during task-based EEG showed an exploratory association with 6-month consciousness-related outcome after brain injury. However, this finding did not survive correction for multiple EEG comparisons and did not significantly improve discrimination beyond age and GCS in this cohort. Task-related EEG connectivity may serve as a candidate complementary marker, but larger multicenter studies with external validation are needed.