A 20-year-old man is found comatose after a high-speed motor vehicle accident. He has no focal neurological deficit and his pupils are equal and reactive. CT brain shows a small area of petechial haemorrhage at the grey-white matter junction of the frontal lobes and a punctate haemorrhage in the corpus callosum, with no mass lesion and normal ventricular size. The most likely diagnosis is:

• A Acute subdural haematoma
• B Cerebral contusion of the temporal pole
• C Traumatic subarachnoid haemorrhage
• D Diffuse axonal injury ✓

Explanation

Diffuse axonal injury results from acceleration-deceleration forces causing shearing of axons at the grey-white matter interface, corpus callosum and dorsolateral brainstem. Coma out of proportion to the CT findings is its hallmark, because much of the injury is microscopic and CT can even appear normal in up to a third of cases. Petechial haemorrhages at characteristic sites, as seen here, support the diagnosis. Subdural and epidural collections produce mass effect, which is absent in this scan.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.