The Glasgow Coma Scale: definition, uses and advantages

The Glasgow Coma Scale (GCS) is a neurological assessment instrument used to assess the level of consciousness of a person with brain damage. It allows you to explore and quantify 3 parameters or criteria of clinical observation: the ocular response, the verbal response and the motor response.

Currently, its use has become widespread to such an extent that It has become the most used tool in the hospital setting and in the pre-hospital field. Among its advantages are its simplicity of application and having provided a common and objective language that facilitates communication between professionals.

What is the Glasgow Coma Scale?

It was designed in 1974 by two English neurosurgeons. members of the Institute of Neurological Sciences at the University of Glasgow: Bryan Jennett and Graham Teasdale. Both published in The Lancet magazine, under the title of Assessment of coma and impaired consciousness, the first version of this scale.

During the 60s, Jennet was creating a database with all cases in which a traumatic brain injury (TBI) had occurred and that had attended in Glasgow, along with other of his collaborators in Holland and the United States. This compilation became the basis on which the Glasglow Coma Scale was created.

Little by little, it became a key tool to objectively assess the state of consciousness of patients who had suffered a TBI. Was divided into 3 categories that individually valued 3 aspects of consciousness: eye opening, verbal response and motor response. And his total score was 14 points.

Renewal with one more point

The definitive version was created two years later, in 1976. It was decided to add a new item that assessed decortication posture, a sign of severe brain damage. This abnormal posture is characterized because the person is rigid with the arms flexed towards the body, the fists of the hands are closed and the legs are very straight.

The 3 subscales were maintained, but the total score with this new addition increased by one point. So, The maximum obtained went from 14 to 15. Thus, it has remained until today.

Applications

Initially, the Glasgow Coma Scale was designed to estimate the severity of patients who had suffered a traumatic brain injury. Currently, it is used to assess less severe states of altered consciousness in post-traumatic situations and other variables, such as the depth of the coma and its duration.

When someone suffers a strong impact to the head, the neurological examination must be carried out as soon as possible. That is, it must be simple, objective and fast. The most important aspect that must be taken into account is the level of consciousness, which is why GCS is key in these cases. So, The score obtained by the patient helps us to know the severity of the injury.

On the other hand, it allows us to identify deep coma states and see their evolution. Hence, its application can be carried out longitudinally (over time) to track the fluctuations of these changes in the level of consciousness.

Scoring and interpretation

Each of the three aspects is assessed by giving a score to the best answer obtained in each category. So, the lowest total score is 3 (1 + 1 + 1) and the highest is 15 (4 + 5 + 6). The severity of the TBI is determined based on this total score and according to the Gennarelli classification in:

Mild: 14 – 15 pointsModerate: 9 – 13 pointsSerious: < 9 points

Regarding the level of altered consciousness (coma state), the gradient varies:

Mild: > 13 points. The duration of the coma is usually less than 20 minutesModerate: 9 – 12 points. The duration of the coma is greater than 20 minutes and less than 6 hours after the patient’s admission.Serious or severe: < 8 points. The duration of the coma is greater than 6 hours after the patient's admission.

Advantages

In the healthcare field, the more precise we are with the terms and concepts we use, the better. For this reason, the Glasgow Coma Scale allows us to avoid the use of ambiguities such as “the patient is drowsy, unconscious or comatose” and to be more rigorous about the clinical status and evolution of the patient. The GCS allows us to gain precision and certainty.

On the other hand, this precision and relative simplicity have caused the rapid universalization of its use, as well as its application to other traumatic and non-traumatic pathologies. It even allows its handling in emergency situations and by different professionals.

It is a complete instrument that assesses 3 key aspects and can be used repeatedly, as it offers longitudinal information about its evolution. That’s why, It is very useful in the early phase of treatment.

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