Table 2. Clinical Criteria for TBI Severity.

Criteria	Mild	Moderate	Severe
Structural imaging	Definition dependent*	Normal or abnormal	Normal or abnormal
Loss of consciousness (LOC)	0-30 minutes	> 30 min and < 24 hrs	> 24hrs
Alteration of consciousness (AOC)**	A moment up to 24 hours	> 24 hours. Severity based on other criteria
Post Traumatic amnesia (PTA)	0-1 day	> 1 and < 7 days	> 7 days
GCS (best score in first 24 hours)	13-15	9-12	< 9

^*Patients who otherwise meet the clinical criteria for mTBI but have intracranial imaging abnormalities may be classified as complicated mTBI or moderate TBI depending on the definition used.

^**Alteration of mental status must be immediately related to the trauma to the head. Typical symptoms may include looking or feeling dazed, confusion, difficulty thinking clearly or responding appropriately to mental status questions, or inability to describe events immediately before or after the traumatic event.

Adapted from: IOM (Institute of Medicine). Gulf War and Health, Volume 7: Long-term Consequences of Traumatic Brain Injury. Washington, D.C.: The National Academies Press; 2009.