Traumatic brain injury is a commonly encountered condition in the emergency department. Mild traumatic brain injury and its sequelae of diffuse axonal injury are difficult to diagnose with computed tomography scans as the preferred acute imaging modality. Our current decision on whether or not to scan a patient in the acute setting is best decided upon by the Canadian CT head rule. The role for MRI scans in diagnosing diffuse axonal injury is unclear, but current evidence suggests that they are preferred after the initial 48-hour period following head trauma.