EEG Correlates of the Confusional State after Traumatic Brain Injury

Area of Science:

• Neuroscience
• Clinical Neurology
• Neurophysiology

Background:

• Post-traumatic amnesia (PTA), now known as post-traumatic confusional state (PTCS), is a critical phase after traumatic brain injury (TBI).
• PTCS shares symptoms with delirium, including memory and attention deficits, suggesting overlapping pathophysiological mechanisms.
• Electroencephalography (EEG) is a promising tool to investigate these mechanisms, particularly diffuse EEG slowing seen in delirium.

Purpose of the Study:

• To assess dynamic EEG correlates of PTCS using the grand total EEG (GTE) score.
• To investigate whether PTCS exhibits similar EEG underpinnings as delirium, specifically diffuse slowing and slow-wave activity.
• To evaluate EEG's potential as an objective biomarker for PTCS severity and recovery.

Main Methods:

• Prospective longitudinal study of 42 TBI patients.
• Patients were classified at baseline (T0) into PTA/PTCS (N=22) and TBI control (N=20) groups using the Confusion Assessment Protocol (CAP).
• Dynamic EEG was assessed using the GTE score, a composite measure of background slowing and superimposed slow-wave activity, at baseline and follow-up (T1).

Main Results:

• Patients in PTA/PTCS showed significantly higher baseline GTE scores (16.6 ± 4.5) compared to TBI controls (5.1 ± 2.8), indicating severe EEG abnormalities.
• Longitudinal follow-up revealed significant EEG improvement (GTE scores dropped from 16.5 to 8) paralleling clinical recovery.
• Higher GTE scores at follow-up correlated with longer PTCS duration (ρ = 0.56, p < 0.0001), independent of medications.

Conclusions:

• PTCS can be reconceptualized as a functional encephalopathy sharing features with delirium, with EEG slowing reflecting reversible cortical dysfunction.
• The GTE score effectively captures dynamic EEG changes associated with PTCS and recovery.
• Clinical EEG, quantified by the GTE score, offers a novel tool for diagnosing, stratifying, and monitoring PTCS in clinical settings.