Table 1:

Classification of TBI severity

(If a patient meets criteria in more than one category of severity, the higher severity level is assigned)
Criteria	Mild	Moderate	Severe
Structural imaging	Normal	Normal or abnormal	Normal or abnormal
Loss of consciousness (LOC)	0–30 min	>30 min and <24 hours	>24 hours
Alterations of consciousness / mental state (AOC)*	Up to 24 hours	>24 hours; severity based on other criteria
Posttraumatic amnesia (PTA)	0–1 day	>1 day and <7 days	>7 days
Glasgow Coma Scale (GCS) (best available score in first 24 hours)**	13–15	9–12	<9

^*Alteration of mental status must be immediately related to the trauma to the head. Typical symptoms would be looking and feeling dazed and uncertain of what is happening, confusion, and difficulty thinking clearly or responding appropriately to mental status questions, and being unable to describe events immediately before or after the trauma event.

^**In April 2015, the DoD released a memorandum recommending against the use of GCS scores to diagnose TBI. See the memorandum for additional information.

Table reproduced from VA/DoD Clinical Practice Guideline for the Management of Concussion-Mild Traumatic Brain Injury.