Unveiling clouded consciousness: Broad-band EEG slowing tracks recovery from post-traumatic confusional state

Post-traumatic confusional state (PTCS) frequently occurs during the recovery from disorders of consciousness (DoC) following severe traumatic brain injury (TBI). Confusional symptoms span multiple domains influencing consciousness, including impairments in the access and integration of mental contents, distortions in perceptual and emotional experiences, vigilance fluctuations, and deficits in memory, orientation, and executive control. While the clinical presentation can be systematically characterized using the Confusion Assessment Protocol (CAP), the underlying neurophysiological mechanisms remain poorly understood. Specifically, slowing of both periodic and aperiodic EEG activity is a consistent finding across multiple alterations of consciousness.

We assessed whether recovery from PTCS involves a renormalization of EEG slowing.

We recorded resting-state EEG from subacute severe TBI patients at admission (T0), comparing patients with PTCS (N=22) to TBI Controls who had already emerged (N = 19). Patients with PTCS were longitudinally monitored using CAP, and a follow-up EEG (T1) was acquired after rehabilitation either upon recovery (N=19) or at discharge (N=3).

Recovery from PTCS was marked by partial normalization of the spectral profile-as indexed by the spectral exponent, and peak frequency-converging toward the profile of TBI Controls. However, marginal persistent elevations in power, indexed by spectral offset and delta power, indicated residual abnormalities. Spectral features, particularly spectral exponent and offset, correlated with CAP and robustly discriminated the presence of PTCS (bivariate model ROC AUC = 0.894).

Results show that PTCS is marked by broadband EEG slowing affecting both periodic and aperiodic activity. Spectral reorganization over time provides insight into the mechanisms of recovery from PTCS and may inform rehabilitation pathways.