Not many years ago, in the world of medicine and psychology, there were many problems in terms of identifying signs of alteration in the level of consciousness (in early stages) of thousands of patients around the world, so that in many cases there were failures in diagnosis, then triggering in negative consequences, because the treatment that was carried out in the same way was not correct.

There was also no general consensus regarding what a “serious” head injury implied , and in different medical parts there were different terms and medical notes of a subjective nature that were not entirely clear: mild coma, deep coma, semi-coma; “he is more conscious today”, etc.

Fortunately, all that has changed, as there is now an internationally recognised scale that allows a very precise and objective assessment of a patient’s level of consciousness. This is the Glasgow Coma Scale .

Characteristics of this tool

The Glasgow Coma Scale was created at the University of Glasgow in 1974 by English neurosurgeons Bryan Jennett and Graham Teasdale. This tool, in general terms, allows the evaluation of the severity of the coma and the assessment of the state of consciousness of the person through tests that are carried out, which revolve around 3 axes: ocular response, motor response and verbal response.

On the other hand, this scale evaluates two aspects in a specific way:

1. Cognitive status

We study the level of understanding that the person may have , this through the compliance or non compliance of the orders that the evaluator asks the evaluator to carry out.

2. The state of alert

The degree to which the person is conscious is studied in the evaluation of the surrounding environment.

Advantages of the Glasgow Coma Scale

This instrument possesses the properties of discrimination, assessment and prediction, something that no other similar instrument possesses to date.

  • Discrimination : thanks to the scale we know which treatment is the most indicated for the patient, this depending on the type and severity of the injury (mild, moderate, etc.).
  • Evaluation : similarly, it allows to evaluate the progress, stagnation and even decrease that the patient has (this can be observed by the application and scoring of the scale repeatedly some time later).
  • Prediction : also manages to estimate a prognosis on the level of recovery that can be expected at the end of treatment.

As far as poor prognosis is concerned, the score obtained from this instrument, and the duration of the coma, represent two very important measures to consider in order to be able to determine the risk of cognitive impairment that may exist. The probability of death is increased in the following cases: comas lasting more than 6 hours, in elderly people, and with scores below 8 (it can be obtained from three to fifteen points).

Common error in application and interpretation

There are cases in which the patient’s limitations are not taken into consideration at the time of evaluation.Sometimes the verbal response is assessed when the person encounters an obstruction in the airway (tracheotomy or endotracheal intubation, for example). It would be a mistake then to apply it to that person, as he or she will obviously not be in condition.

Another mistake, and which goes in the same direction as the previous one, is to assess the motor response when the person is sedated or has some neuromuscular blocker in his body.

What is appropriate in these cases is not to evaluate it with a specific digit, but rather to record it as “non-valuable”, because if it is applied and qualified as if it had no impediments, there is the possibility that the medical report will leave the impression that the situation is very serious, because there would be a record of 1 point in that area, and perhaps the person evaluated could obtain the 5 points, but not at that moment that it was applied, just as we have seen, there was an object that did not allow him to perform the test in the best possible way; There were limitations that were not related to anything neurological , and we must continue with the subscales that can be evaluated.

Basic characteristics

The Glasgow Coma Scale has two very valuable aspects that have given it the opportunity to be the most widely used instrument in several medical units for making assessments of the level of consciousness:


Being a user-friendly tool, communication between different health professionals (including non-specialists such as nurses, paramedics, etc.) was greatly improved, as understanding between the parties was much greater, as they all had “the same channel” of communication.


The use of a numerical scale leaves aside any appreciation that may be considered subjective, there is no room here for different interpretations by different evaluators; in this case it is more likely to be whether it presents eye-motor-verbal movement, or not, adding points or having a point in that item.

Bibliographic references:

  • Antonio, P. P. (2010). Introduction to Neuropsychology. Madrid: McGraw-Hill.
  • Muñana-Rodríguez, J. E., & Ramírez-Elías, A. (2014). Glasgow Coma Scale: origin, analysis and appropriate use. University Nursing, 11(1), 24-35.