Glasgow Coma Scale (GCS)

Introduction

The Glasgow Coma Scale (GCS) is the most widely used tool for assessing a person’s level of consciousness. Graham Teasdale and Bryan Jennett, neurosurgeons at the University of Glasgow, introduced it in 1974. It was originally designed for patients with head injuries, but it’s now used across emergency medicine, intensive care, and neurology to track consciousness over time. It scores three types of response separately, so it gives a consistent shared language for describing a patient’s condition and spotting changes.

How it’s scored: The three component scores of the Glasgow Coma Score are added for a total from 3 (no response) to 15 (fully alert and oriented). An additional result is also recorded as a Glasgow Coma Scale (E3 V3 M4), because the same total can describe very different patients.

*Individual components may be not testable due to any of the following (note this is not a comprehensive list):

• Eye: local injury and/or edema.

• Verbal: intubation.

• All (eye, verbal, motor): sedation, paralysis, and ventilation eliminating all responses. 

Untestable components: Sometimes a response can’t be tested. A patient who is intubated can’t speak, and swelling may keep the eyes shut. That component should be recorded as NT (not testable), not scored as 1, because a score of 1 means “no response” and would make the patient appear more impaired than they are. In that case the components are reported individually, for example “E3 V-NT M5,” rather than combined into a total. Some hospitals add a “T” suffix for intubated patients, such as “8T,” but that’s a local convention, not official scoring.

Results

• The Glasgow Coma Score is calculated by addition of the total points selected under each component (eye, verbal, motor) below, e.g. "15 points".

• The Glasgow Coma Scale is comprised of the individual components, e.g. "E(4) V(5) M (6)".

How results are interpreted: For traumatic brain injury, totals are commonly grouped as 13–15 mild, 9–12 moderate, and 3–8 severe. A score of 8 or less signals a severely reduced level of consciousness, and is often used as a threshold to consider protecting the airway. A falling score over repeated checks is a warning sign that needs urgent assessment, even if each single score looks moderate.

Management Considerations

• If a component is untestable, a score of 1 should not be assigned (Teasdale 2014). In this circumstance, summation of the findings into a total Glasgow Coma Score is invalid.

• Clinical decisions should not be based solely on the GCS score.

• Consider intubation if the GCS ≤8 and there is clinical concern the patient is unable to protect their airway or that they have an expected worsening clinical course based on exam or imaging findings.

• A rapidly declining or waxing and waning GCS is concerning and intubation should be considered in the context of the patient's overall clinical picture.

Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974 Jul 13;2(7872):81-4.