|Traumatic brain injury has been defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force. Classification of TBI is based on the length of loss of consciousness, Glasgow Coma Scale score and length of post-traumatic amnesia. A GCS score of 13-15 is characterised as a mild TBI, a GCS of 9-12 is categorised as a moderate TBI, and a GCS of 3-8 is characterised as a severe TBI.
Post-traumatic amnesia is an important predictor of functional outcome. Levin defined post-traumatic amnesia as the interval during which the patient is confused, amnesic for ongoing events and likely to show behavioural disturbance. More recently posttraumatic amnesia has been defined as the interval from the injury until the patient is orientated and can form and later recall new memories. A PTA up to 24 hours has been categorised as a mild TBI, a PTA between 1-7 days a moderate TBI, and PTA beyond 7 days has been characterised as a severe TBI.
Improving the Classification of Traumatic Brain Injury: The Mayo Classification System for Traumatic Brain Injury Severity: Daniel Philip Friedland.