Focal Electroencephalographic Changes Index Post-Traumatic Confusion and Outcome.

While the duration and severity of post-traumatic confusional state (PTCS) after traumatic brain injury have well-established implications for long-term outcomes, little is known about the underlying pathophysiology and their role in functional outcomes. Here, we analyzed the delta-to-alpha frequency band power ratios (DAR) from localized scalp areas derived from standard resting electroencephalographic (EEG) data recorded during eyes closed state in 49 patients diagnosed with PTCS. Higher global, occipital, parietal, and temporal DARs were significantly associated with the severity of PTCS, as assessed by the Confusion Assessment Protocol (CAP) observed on the same day, after controlling for injury severity. Also, occipital DARs were positively associated with both the CAP disorientation score 2, and the CAP symptom fluctuation score 4, after controlling for injury severity (n = 35). Posterior DARs were significantly associated with Functional Independence Measure-cognitive subscale average score at 1 (n = 45), 2 (n = 42), and 5 (n = 34) year(s) post-injury. The associations at 1 (temporal left) and 2 (parietal left) years survive after controlling for an injury severity index. Our finding that posterior DAR is a marker of PTCS and functional recovery post-injury, likely reflects functional de-afferentation of the posterior medial complex (PMC) in PTCS. Altered function of the PMC is proposed as a unifying physiological mechanism underlying both acute and chronic confusional states. We discuss the relationship of these findings to electrophysiological markers associated with disorders of consciousness.