Most usually, the history of events before and after the injury must be obtained from witnesses or ambulance staff.
Important points to determine include:
- period of altered consciousness } indicates severity of
 - period of post traumatic amnesia} diffuse brain damage
 - cause and circumstances of injury - violent injuries, e.g. road traffic accidents, are associated with greater risk of extracranial injuries. Ask about relevant medical history - e.g. epilepsy.
 - presence of headache - if persistent, raises possibility of intracranial haemorrhage
 - presence of vegetative features - e.g. vomiting, inappropriate salivation, abnormal sweating/shivering, respiratory disturbances, e.g. Cheynes-Stokes breathing, hyperventilation; suggests brain stem lesions.