The lowest possible Glasgow Coma Scale score is 3, not zero
Emergency teams worldwide rate consciousness from 3 to 15 by testing just three things: the eyes, speech and movement. Two Glasgow doctors built the scale in 1974 because a dozen earlier coma scales were vague, confusing and impossible to repeat at the bedside, and it is still standard trauma training today.
Head injuries were climbing during the 1960s, partly because more people were travelling by motor vehicle, and doctors worried that poor recovery reflected poor assessment. By 1974 there were 13 published coma scales, none widely used. Their categories were fuzzy, their terms overlapped, and many were too cumbersome to repeat frequently on the ward. Bryan Jennett and Graham Teasdale at the University of Glasgow set out to design something simple enough to use without special training, reliable, clinically useful and quick to repeat.
Their scale scores three responses separately: eye opening, verbal reply and motor response, always taking the best response the patient can give. A fully alert person scores 15, and someone completely unresponsive scores 3, because each test bottoms out at 1. Scores from 3 to 8 usually indicate coma. The components are recorded alongside the total, in forms such as GCS 12 made up of E3, V4 and M6, and a time is often noted too. If a breathing tube or swollen eyes make a test impossible, a letter modifier marks it, such as t for tube or c for closed.
The original motor test had five levels because staff struggled to tell normal flexion from abnormal flexion. Teasdale later split them after finding that trained personnel could distinguish the two and that they predicted different outcomes, making six motor levels the standard. He had not planned for anyone to add the scores together, but the total turned out to correlate with death and disability, so the summed score became common shorthand in research and practice, though it is not recommended as a stand-alone predictor.
Nurses in Glasgow's neurosurgical unit adopted it first. Its spread accelerated in 1978, when Tom Langfitt urged neurosurgical units to use it and it entered the first Advanced Trauma Life Support course. Limits remain: very young children need a paediatric version, and elderly patients may score well despite serious injury after something as minor as a fall from standing.
Source: Glasgow Coma Scale
