Longitudinal Multimodal Neuroimaging After Traumatic Brain Injury

Area of Science:

• Neuroscience
• Radiology
• Neurology

Background:

• Traumatic brain injury (TBI) is a leading cause of long-term cognitive impairment.
• Mechanisms of TBI recovery and the relationship between cellular and functional changes are poorly understood.
• Multimodal neuroimaging offers insights into TBI-related pathologies.

Purpose of the Study:

• To longitudinally investigate TBI-related pathologies using multimodal neuroimaging.
• To correlate changes in flumazenil PET binding potential, diffusion MRI (dMRI)-derived structural connectivity, and resting-state fMRI-derived functional connectivity and amplitude of low-frequency fluctuations.
• To explore the evolving interplay between neuronal integrity, structural connectivity, and functional dynamics post-TBI.

Main Methods:

• Longitudinal multimodal neuroimaging analysis in individuals with complicated mild-to-severe TBI.
• Quantification of four biomarkers: flumazenil PET binding potential, dMRI structural connectivity, fMRI functional connectivity, and fMRI amplitude of low-frequency fluctuations.
• Correlational analysis between biomarkers at subacute (4-6 months) and chronic (1 year) stages post-injury.

Main Results:

• Reduced flumazenil-PET binding potential in frontal and thalamic regions, with partial recovery over time.
• Initial functional hyperconnectivity in TBI subjects that declined but remained elevated; persistent cortical structural hypoconnectivity.
• Increased correlation between MRI modalities and flumazenil-PET at the chronic stage, suggesting convergence of disruptions.
• Heightened intrinsic regional activity as a potential compensatory mechanism in disconnected regions.

Conclusions:

• Multimodal neuroimaging reveals complex, dynamic changes in TBI recovery.
• Structural and functional disruptions progressively converge over time post-TBI.
• Compensatory mechanisms may play a role in managing progressive axonal degradation and functional decline.