The Role of MRI in Debunking the Fallacy of "Mild" Traumatic Brain Injury.

Mild traumatic brain injury (mTBI) is a prevalent yet often overlooked public health concern due to the absence of detectable abnormalities on CT or conventional MRI scans. Approximately 18.3%-31.3% of mTBI patients experience persistent symptoms 3-6 months post-injury, despite normal imaging results, making diagnosis and treatment challenging. In recent years, advanced neuroimaging modalities have emerged with the potential to reveal subtle physiological and structural brain changes that are invisible to traditional imaging. Diffusion MRI (dMRI), for instance, is particularly valuable for detecting white matter injury; perfusion MRI assesses alterations in cerebral blood flow; sodium MRI (²³Na MRI) provides insights into ionic homeostasis; and functional MRI (fMRI) detects disruptions in functional brain network connectivity. In this review, we first explore the underlying mechanisms of mTBI and then summarize current evidence supporting the use of advanced MRI techniques to detect injury signatures associated with these mechanisms. Finally, we highlight populations at heightened risk for repeated injuries-underscoring the urgent need for more sensitive diagnostic tools that can identify injury early, guide return-to-activity decisions, and prevent cumulative brain damage. EVIDENCE LEVEL: N/A. TECHNICAL EFFICACY: Stage 3.