A motorcyclist is found deeply unconscious immediately at the scene of a high-speed collision with no lucid interval. Initial CT head is nearly normal apart from subtle swelling. Repeat imaging shows multiple small punctate haemorrhages at the grey-white matter junction and in the corpus callosum. Which mechanism best explains these findings?

• A Tearing of bridging cortical veins producing venous haemorrhage
• B Direct coup contusion beneath the point of impact
• C Rupture of the middle meningeal artery against the pterion
• D Shearing of axonal fibres from differential acceleration and deceleration forces ✓

Explanation

Diffuse axonal injury results from angular acceleration and deceleration that shear axons at interfaces of differing density, classically the grey-white matter junction, corpus callosum and dorsolateral brainstem. It causes immediate loss of consciousness without a lucid interval, and early CT may look deceptively normal while MRI shows far more. Bridging vein tearing produces subdural haematoma instead, middle meningeal rupture produces extradural haematoma, and coup contusion requires a focal impact site, none of which matches this diffuse pattern.

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.