TBI's are generally graded as mild, moderate, or severe. Mild TBIs include concussions; these generally do not show lesions on MRI or CT scans. TBIs are specified as "mild complicated" or moderate when imaging shows evidence of lesion(s). While consensus is lacking regarding a definitive indicator of TBI severity, indices used for documenting TBI severity include:

• Length of Loss of Consciousness (LOC)
• Glasgow Coma Scale (indication of disturbed consciousness)
• Ranchos Los Amigos Scale
• Length of Post-traumatic Amnesia

Loss of Consciousness (LOC)

Duration of loss of consciousness (coma) following head trauma has historically been used as an indicator of TBI severity. However, significant TBIs do not necessarily lead to LOC, and research suggests that duration of LOC may not always be closely correlated with outcome. With these caveats in mind, below is one often used set of criteria for classifying TBI based on coma duration.

Glasgow Coma Scale (GCS)

This brief scale provides indication of disturbed consciousness. Scores range from 3-15; points are assigned based on best eye, verbal, and motor responses.

• Score of 13-15 => Mild TBI
• Score of 9-12 => Moderate TBI
• Score of < 8 => Severe TBI

The Glasgow Coma Scale

Rancho Los Amigos Scale

This scale provides a longer-term indicator of functioning, which can be used for tracking recovery, considering prognosis, planning and placement decisions, and measuring treatment effects and outcomes.

The Rancho Los Amigos Scale (Levels of Cognitive Functioning)

1. No response – the patient is fully unresponsive to sounds, movement, and touch (deep coma).
2. Generalized response – the patient responds inconsistently, nonpurposefully, and nonspecifically.
3. Localized response – the patient responds specifically to stimuli, but exhibits variable responses to stimuli, commands, orienting, and withdrawing
4. Confused-Agitated – the patient has trouble processing information and maintains an elevated level of activity
5. Confused, inappropriate – the patient is alert and can respond to simple commands with some level of consistency; he/she has significant difficulty with lack of structure and increased complexity
6. Confused-Appropriate – the patient displays goal-directed behavior, but requires external direction
7. Automatic-Appropriate – the patient demonstrates appropriateness and correct orientation at home and the hospital, but has a shallow recall of what he/she has done, may not fully understand or appreciate his/her own deficits
8. Purposeful and appropriate – the patient is alert and oriented; his/her memory is intact for recent and remote events, and maintains awareness and responsiveness to his/her environment

Posttraumatic Amnesia (PTA)

Assessment of this indicator of injury severity is not reliant on a specific scale. Rather, PTA refers to the absence of clearly formed memories for events following the TBI. In general, the absence of recall for longer periods of time generally indicates a more severe injury.

TBI Severity Classified by PTA Duration

Retrograde Amnesia (RTA)

Also not reliant on a specific scale, assessment of RTA involves determining the period of time prior to the head trauma for which the injured person has no clearly formed memories. In general, greater duration indicates a more severe injury. However, this is viewed as a less sensitive indicator of injury severity.