In pediatric traumatic brain injury, which imaging finding is most specific for diffuse axonal injury?

• A. Diffuse edema without hemorrhage
• B. Hemorrhage in subdural space
• C. Microhemorrhages on SWI or gradient-echo sequences.
• D. Enlarged ventricles on CT

Answer: (C)

Diffuse axonal injury is driven by shearing forces that tear axons across white matter tracts, often leaving tiny bleeds that are hardest to see on standard imaging. The most specific sign on modern imaging is tiny hemorrhages in the white matter detected on susceptibility-sensitive sequences like susceptibility-weighted imaging (SWI) or gradient-echo (GRE) MRI. These microhemorrhages reflect the microscopic vascular disruption accompanying axonal injury and tend to occur in characteristic locations such as the corpus callosum and brainstem. CT can miss them, and findings like diffuse edema without hemorrhage or a subdural hemorrhage reflect other injury processes, not DAI. Enlarged ventricles can indicate other problems like hydrocephalus or brain atrophy, not DAI. So, seeing microhemorrhages on SWI or GRE is the imaging feature most specific for diffuse axonal injury in pediatric TBI.