Severity classification is done with several different tools including the widely used Glasgow Coma Scale (GCS).

The scale recognizes three levels of severity for traumatic brain injury: mild, moderate, and severe. An injured person’s eye responses, verbal responses, and motor responses are measured. The lowest score on the GCS is a three, meaning that a person does not open their eyes, makes no sounds, and makes no movements. A person with a score of three on the GCS is in a deep coma. The highest possible score is a 15.

It is very important to know that the GCS is helpful primarily in the assessment of severe brain injury. Dr. Bryan Jennett the author of the GCS Scale, states the following about the scale in the publication, Mild Head Injury, c.Oxford, 1989, page 24, “It was not intended as a means of distinguishing among different types of milder injury. Many of these patients are oriented by the time they are assessed and therefore score at the top of the Glasgow scale. Yet some of these patients have had a period of altered consciousness, either witnessed or evidenced by their being amnesic for events immediately following injury. Impairment of consciousness is indicative of diffuse brain damage, but there can also be marked local damage without either alteration in consciousness or amnesia.”