What is GCS - Glasgow Coma Scale 

The Glasgow Coma Scale, also known as the GCS, is a tool used to measure levels and states of consciousness. The tool is used primarily for assessment of patients in a coma or in ICU. 

The concept was proposed by Graham Teasdale, and Bryan J. Jennett, professors of neurosurgery at the University of Glasgow, in 1974. The results were published in Lancet,  a prominent medical journal, and to tool has been widely used since owing to its simplicity. 

The tool ultimately combined various basic tests on the abilities of a person to respond, which in turn provide information on brain function in key areas, which overall constitute the scale. It was the idea of formalizing a scale, based on consistently understood indicators which could provide rigor to our understanding of consciousness, or lack thereof, along a spectrum.

Appropriate use of GCS

The development of the GCS was specifically related to cases of traumatic brain injury, but the applications are broader and more varied. The GCS has also been used as a factor in other medical diagnostic tools including the Revised Trauma Score, which quantifies the degree of injury for prioritization of treatment; or APACHE II, a mortality prediction tool.

GCS is appropriate to use under the following circumstances:

•	After major trauma
•	Where there is a loss of consciousness
•	Where there is suspected injury to the spinal cord, or nervous system (decortication, or decerebration)
•	For comatose patients
•	As part of an on-going assessment for all ICU patients

The Glasgow Coma Scale works on gathering data using a simple four, five, or six point scaling system, depending on the level of response. 

There are three aspects to the framework.

1.	Eye Response (E4)
Eye response uses a 4-point scaling system, measured by whether the eyes open naturally, or spontaneously in response to stimuli such as pain.

2.	Verbal Response (V5)
Verbal response uses a 5-point scale relating to a verbal response, such as clear speech, incoherent speech, some sound, or no sound at all.

3.	Motor Response (M6)
The motor-response scale, a 6-point scale is measured based on the levels of movement, and the extent to which these can be controlled by the patient. The scale would consider whether the person is moving or not, whether limbs will withdraw from pain, and whether the patient can move a limb to follow an instruction; i.e. at will.

By developing a quantified and standardized system, the GCS is able to create a framework for studying cases. This, combined with the recording of outcomes of recovery begins to provide a framework of how to implement treatment and what outcomes to expect.

The following table outlines the complete detail of this scaling system:



From this table, you can simply enter the observed values into the GCS calculate to get the overall Glasgow Coma Scale score. 

It should be noted that we separate scores for children ages 2 – 5 and 0 – 23 months in terms of the classification of each numbered score.

In order to calculate the GCS, you simply add the 3 numbers from assessing the patient for eye response, motor response, and verbal response.

The GCS Score

If a patient cannot open their eyes, cannot make a sound, and cannot move, their GCS score is 3. This is a ranking of 1 for each of the indicators in the test. This is the lowest possible GCS score. From this scaling system, the GCS enables doctors to classify brain injury according to the following classified severities:

•	Minor (GCS 13 – 15)
•	Moderate (GCS 9 – 12)
•	Severe (GCS 3-8)

A score between 3 and 8 is considered a coma. It is generally considered that scores of 8 and above provide a good chance of recovery.

Challenges

The GCS does pose some challenges in that it was never intended to simply be the sum of 3 scores. Although it was used to some extent, and in other applications as a prognostic tool, it is argued that this measure is not sufficiently complex to be able to infer outcomes. The brain and nervous system are highly complex, and the interplay between the vision, verbal and motor functions has not been sufficiently considered. For example, in diagnostic tools which aim to predict mortality, the same GCS score (for example a score of 4 comprised of lower verbal and eye response, but higher motor response) predicts a far higher mortality rate than the same score where the verbal and motor response s far lower, but the eyes open.