How does one assess severity of brain injury i.e. is the brain injury considered to be mild, moderate or severe? Threshold values relating to period of loss of consciousness, Glasgow Coma Scale and length of Post Traumatic Amnesia are applied in order assess severity.  Please refer to chart below.  These measures help predict long term prognosis.

 

The most commonly used severity ratings in brain injury are based on:

Mild Moderate Severe
Loss of Consciousness ≤ 30 minutes 30 minutes – 24 hours > 24 hours
Glasgow Coma Scale Score ≥ 13 9 – 12 < 9
Post Traumatic Amnesia ≤ 1 day 2 – 7 days > 7 days

Defining Good versus Poor Outcomes Following Brain Injury
How does one quantify outcomes between good and poor recovery? The Glasgow Outcome Scale is a commonly used measure of recovery and is measured as follows:

  • Dead.
  • Vegetative State (Unable to interact with environment; unresponsive).
  • Severe Disability (Able to follow command but unable to live independently).
  • Moderate Disability (Able to live independently but unable to return to work, school or other previous social roles).
  • Good Recovery (Able to return to work, school or other previous social roles).

Linking Threshold Values to Outcome Scales:

  • Generally one would expect a poorer outcome following a brain injury which is assessed as severe; equally one can occasionally see a good outcome following a severe brain injury.
  • Therefore there is no threshold level above or below which one can reliably predict a poor or a good outcome.
  • Thus there are some patients who might be in the three severe categories above who eventually have a good outcome and conversely some in all three mild categories who do not make a good recovery.
  • Initial severity is not reliable in predicting the rate of recovery.
  • Appearances on diagnostic imaging (MRI or CT scanning) can also be quantified in terms of severity but again without providing specific predictive values.