Brain State Entropy as a Marker of Injury Severity and Sedation Effects Following Traumatic Brain Injury

Area of Science:

• Neuroscience
• Medical Imaging
• Systems Biology

Background:

• Traumatic brain injury (TBI) disrupts large-scale brain networks, affecting cognitive function.
• Dynamic functional connectivity (dFC) analysis reveals time-varying interactions within brain networks using fMRI.
• Understanding dFC alterations in TBI is crucial for prognosis and treatment.

Purpose of the Study:

• To investigate dFC in subacute moderate-to-severe TBI patients.
• To explore the relationship between dFC, injury biomarkers, and propofol sedation.
• To determine if dFC predicts long-term functional outcomes after TBI.

Main Methods:

• Sixty-five TBI patients and 48 controls underwent resting-state fMRI and diffusion-weighted imaging.
• dFC was analyzed using a sliding-window approach and k-means clustering to identify brain states.
• Blood biomarkers (e.g., GFAP, NFL) and white matter integrity (FA) were measured.

Main Results:

• TBI patients exhibited reduced temporal flexibility, less anticorrelated network activity, and fewer state transitions.
• Reduced brain state entropy correlated with elevated blood biomarkers and decreased white matter integrity.
• Propofol sedation significantly reduced entropy; GFAP was the strongest predictor of entropy.

Conclusions:

• Moderate-to-severe TBI disrupts dFC, characterized by reduced brain state entropy and flexibility.
• These disruptions are linked to injury severity and exacerbated by sedation, impacting prognosis.
• Preserved or normalized brain state entropy predicts better functional outcomes and biomarker changes post-TBI.