Teaching NeuroImages: Usefulness of susceptibility-weighted sequences after traumatic brain injury.

Three weeks after severe traumatic brain injury (pedestrian hit by a car) and correction of initial intracranial hypertension, a brain MRI is performed in a 22-yearold woman, who remains in a comatose state (Glasgow Coma Scale at 4, with withdrawal to painful stimuli; abolition of photomotor reflex; persistence of corneal and cough reflexes). Fluid-attenuated inversion recovery and T2*-weighted gradient-echo sequences reveal subtle hyperintensities within the brainstem. On susceptibilityweighted imaging, extensive diffuse axonal injuries are identified in the brainstem, thalami, corpus callosum, and frontal lobes, which explain the clinical state (figure). Susceptibility-weighted imaging is a gradient-echo sequence combining phase and magnitude information, Figure Brain MRI