Figure 9. CT and MR appearance of traumatic axonal injury.

Initial noncontrast CT (A) of a 24-year-old female after a helmeted bicycle accident with brief loss of consciousness shows right periorbital soft tissue swelling, but is otherwise normal. MRI (including T2*-weighted MPGR (B), DWI (C) and ADC map (D) obtained the following day shows scattered foci of reduced diffusion and increased susceptibility, compatible with traumatic axonal injuries. Example lesions include a focus of reduced diffusion (C, arrow) with low ADC value (D, arrow) and foci of increased susceptibility (B, arrow) in the left temporal stem subcortical white matter. A different patient presented after an assault (E-H). This patient's noncontrast CT shows multiple areas of hemorrhagic axonal shearing injury involving the splenium of the corpus callosum (E, arrow). This area shows reduced diffusion (G, arrow), low ADC value (H, arrow) and increased susceptibility on MPGR (F, arrow) on MRI performed the same day. The coronal MPGR image (F) also reveals numerous additional white matter shear injuries (low signal) compatible with diffuse axonal injury.