Prolonged unconsciousness from which the individual cannot be aroused, associated with traumatic injuries to the BRAIN. This may be defined as unconsciousness persisting for 6 hours or longer. coma results from injury to both cerebral hemispheres or the reticular formation of the brain stem. Contributing mechanisms include diffuse axonal injury and brain edema. (From J Neurotrauma 1997 Oct;14(10):699-713)