Immediate Loss of Consciousness After Head Trauma: 5 Mechanisms

Acute post-traumatic unconsciousness results from several biomechanical and pathophysiological mechanisms:

1. Concussion (mTBI): Transient neuronal dysfunction from rotational/shear forces; LOC seconds-minutes
2. Coup-Contrecoup Injury: Impact at site (coup) + countercoup contra-lateral injury; contrecoup often more severe
3. Diffuse Axonal Injury (DAI): Widespread axonal shearing from acceleration-deceleration; often prolonged LOC
4. Intracranial Hemorrhage: Epidural, subdural, subarachnoid, or intraparenchymal bleeding → mass effect, herniation
5. Brain Herniation: Uncal, central, or tonsillar herniation from edema/hemorrhage → brainstem compression → coma

Any LOC after head trauma requires emergent neuroimaging and neurosurgical evaluation.