Hong Life CalculatorsUnderstanding the Glasgow Coma Scale — concept and principle
The Glasgow Coma Scale (GCS) describes a person's level of consciousness by scoring three kinds of response: eye opening, verbal response and motor response. It is used after head injury, in stroke and in any acutely ill patient, and repeated over time to detect improvement or deterioration.
How it is calculated
- Eye opening (E): 4 spontaneous, 3 to sound, 2 to pressure, 1 none.
- Verbal (V): 5 oriented, 4 confused, 3 words, 2 sounds, 1 none.
- Motor (M): 6 obeys commands, 5 localising, 4 normal flexion, 3 abnormal flexion, 2 extension, 1 none.
GCS = E + V + M, from 3 to 15. The calculator also shows the notation (for example E4 V5 M6) and the head-injury severity band: 13–15 mild, 9–12 moderate, 3–8 severe.
The principle
Teasdale and Jennett (1974) designed the scale so that different observers, at different times, would describe the same patient in the same way. Each component is an ordered list of the best response achieved, from normal to absent, so each level is observable rather than interpreted. The motor score carries the most prognostic weight, because it remains measurable when the eyes are swollen shut or the patient is intubated. The total is convenient, but the same total can arise from very different patterns, which is why current guidance asks for each component to be reported.
Worked example
- Defaults: eyes open spontaneously (E4), oriented speech (V5), obeys commands (M6).
- GCS = 4 + 5 + 6 = 15.
- Notation: E4 V5 M6.
- 15 is 13 or more, so the head-injury band is mild.
How to read the result
15 is fully alert. A fall of 2 or more points, or of 1 point in the motor score, is an important sign of deterioration that needs prompt review. A score of 8 or less is commonly taken to mean coma and prompts assessment of airway protection. Record the time of each assessment so trends are reliable.
Common mistakes
- Reporting only the total, for example "GCS 10", without E, V and M.
- Scoring verbal response in an intubated patient instead of recording it as not testable (often written VT or NT).
- Applying pressure incorrectly; standard sites are the fingertip, the trapezius and the supraorbital notch.
- Using the adult verbal scale for young children, who need a paediatric version.
Frequently asked questions
What is the lowest possible GCS?
3, because each component starts at 1 even when there is no response.
What changed in the 2014 update?
Terms were clarified, for example "to pain" became "to pressure" and the flexion responses were renamed, and the use of non-testable (NT) ratings was emphasised.
Is there a version for children?
Yes. A paediatric GCS adapts the verbal and some motor descriptions for children who cannot yet speak.
Sources: Teasdale G., Jennett B., Lancet, 1974 · Teasdale G. et al., The Glasgow Coma Scale at 40 years: standing the test of time, Lancet Neurology, 2014 · glasgowcomascale.org (official assessment aid)