While the duration and severity of post-traumatic confusional state (PTCS) following 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 analysed 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 post-traumatic confusional state. Higher global, occipital, parietal and temporal DARs were significantly associated with Confusion Assessment Protocol (CAP) severity symptoms 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 symptom fluctuation score 4, after controlling for injury severity (n=35). Posterior DARs were also 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 post-traumatic confusional state and functional recovery post-injury likely reflects functional deafferentation of the posterior medial complex in PTCS. Altered function of the posterior medial complex is proposed as a unifying physiological mechanism underlying both acute and chronic confusional states. We discuss the relationship of these findings to electrophysiologic markers associated with disorders of consciousness.ulations is proposed as the basis of our findings.