Table 1

Comparison of existing ACRM mTBI definition criteria to suggested revisions by 2021 expert panel

1993 ACRM criteria32021 expert panel suggested revision4
A patient with mTBI is a person who has had a traumatically induced physiological disruption of brain function, as manifested by at least one of the following:

  1. any period of LOC;

  2. any loss of memory for events immediately before or after the accident;

  3. any alteration in mental state at the time of the accident (eg, feeling dazed, disoriented or confused);

  4. focal neurological deficit(s) that may or may not be transient; but where the severity of the injury does not exceed the following:

    • LOC of approximately <30 min;

    • after 30 min, an initial GCS of 13–15;

    • PTA not greater than 24 hours.

Diagnostic criteria for mTBI should:

  1. specify that alternative explanations for altered mental status must be ruled out;

  2. incorporate levels of certainty (eg, possible, probable and definite categories) rather than be binary;

  3. distinguish between mTBI without; neuroimaging evidence of intracranial trauma;

  4. include a maximum timeframe for the onset of symptoms;

  5. be expanded to include other observable signs (eg, blank/vacant look or motor incoordination);

  6. include a minimum duration of symptoms.


Neuroimaging evidence of intracranial trauma implies a more severe form of TBI, not an mTBI.
The terms ‘concussion’ and ‘mild traumatic brain injury’ can be used synonymously.
Rapid-onset postconcussion symptoms after head/neck trauma should indicate at least a possible mTBI.

  • ACRM, American Congress of Rehabilitation Medicine; GCS, Glasgow Coma Scale; LOC, loss of concisouness; mTBI, mild traumatic brain injury; PTA, post-traumatic amnesia.