A 20-year-old motorcyclist is brought in comatose (GCS 6) immediately after a high speed collision. He was never lucid. CT brain shows no extradural or subdural collection and no contusion large enough to explain coma, but demonstrates multiple small petechial haemorrhages at the grey white matter interface and in the corpus callosum. MRI would show microstructural white matter disruption. The most likely diagnosis is:
- A Traumatic subarachnoid haemorrhage
- B Brainstem contusion
- C Diffuse axonal injury ✓
- D Delayed intracerebral haematoma
Explanation
Immediate prolonged coma after rotational acceleration deceleration injury, with petechial haemorrhages at the grey white junction and corpus callosum on CT, is classic for diffuse axonal injury. Shearing forces disrupt axons at the moment of impact, so coma occurs without a mass lesion. CT may even appear normal initially, and MRI with susceptibility sequences is more sensitive. Isolated traumatic subarachnoid blood or a focal brainstem contusion does not produce this characteristic distribution, and delayed intracerebral haematoma presents with progressive deterioration.
Reference: Youmans and Winn Neurological Surgery; Greenberg Handbook of Neurosurgery, 9th ed.
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Written and medically reviewed by the StethoPrep medical team.