A 24-year-old man remains deeply comatose (GCS E1VTM2) after a high-speed motor vehicle accident. Pupils are equal and reactive and there are no focal neurological signs. Initial CT head appears essentially normal apart from tiny petechial haemorrhages near the grey-white junction and corpus callosum. The most likely diagnosis explaining coma disproportionate to the CT findings is:

• A Diffuse axonal injury ✓
• B Acute subdural haematoma too small to detect on CT
• C Post-traumatic basilar artery thrombosis
• D Non-convulsive status epilepticus after concussion

Explanation

Diffuse axonal injury results from high-speed rotational acceleration and deceleration forces shearing axons at the grey-white junction, corpus callosum and brainstem. Coma is immediate and prolonged yet CT may show only small petechial haemorrhages or appear normal, because the injury is microstructural. MRI with gradient echo or diffusion sequences demonstrates the lesions far better and carries prognostic weight. An occult subdural large enough to cause deep coma would be visible on CT, and vascular occlusion produces focal deficits.

Reference: Sabiston Textbook of Surgery, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.