Defining MTBI

In 1993 the American Congress of Rehabilitation Medicine (ACRM) generated a standardized definition of MTBI.

MTBI is a "traumatically induced physiological disruption of brain function" which involves at least one of the following:

  • Any period of loss of consciousness;
  • Any loss of memory for events immediately before or after the accident;
  • Any alteration in mental state at the time of accident (e.g., feeling dazed, disoriented, or confused);
  • Focal neurological deficit(s) that may or may not be transient

But where the severity of the injury does not exceed the following:

  • Loss of consciousness of approximately 30 minutes or less;
  • After 30 minutes, an initial Glasgow Coma Scale (GCS) of 13-15;
  • Post-traumatic amnesia (PTA) not greater than 24 hours.


The definition includes either a blow to the head or no blow to the head but a shaking of the head from acceleration/deceleration movement (i.e., whiplash).

The definition does not include strokes, anoxia, tumors, encephalitis, or other such conditions.

          CT scans; MRI, EEG, or routine neurological evaluations may be normal.

The definition also acknowledges that due to inadequacies of some medical systems some of the above factors are not documented during the acute phase.

In situations where there is a history of head trauma, it is prudent to review ongoing symptoms in light of a possible MTBI.

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