Glasgow Coma Scale


The Glasgow Coma Scale (GCS) was first created by Graham Teasdale and Bryan Jennett in 1974. It is a clinical scale to assess a patient’s “depth and duration of impaired consciousness and coma” [1] following an acute brain injury. Healthcare practitioners can monitor the motor responsiveness, verbal performance, and eye-opening of the patient in the form of a simple chart. The GCS is the most commonly used tool internationally for this assessment and has been translated into 30 languages. It should not, however, be confused with the Glasgow Outcome Scale (GOS), which evaluates persistent disability after brain damage. [2]

Intended Population

The Glasgow Coma Scale was originally developed to help determine the severity of a coma or dysfunction following a traumatic brain injury, but can be useful for any condition leading to impaired consciousness. [3] Today, it is consistently used for many conditions including stroke (subarachnoid haemorrhage, intracerebral haemorrhage, or ischemic stroke), infection, seizures, brain abscess, general traumas, non-traumatic coma, overdose and poisoning. [3] It can also be administered in a variety of settings such as pre-hospital, arrival at the emergency department and in the hours following admission, giving it the ability to monitor changes and trends in patient consciousness over time. [3] Modified scales have been developed for use in other populations. The Glasgow Coma Scale - Extended (GCS - E) includes the use of an amnesia scale in order to avoid the premature discharge of patients with mild traumatic brain injury. [4] There have also been modified scales developed for use in the pediatric population. The motor scale has proved the most useful for assessment in both older children and preverbal children when studying blunt trauma. [5] Research has indicated that using the motor scale alone can simplify the assessment process while maintaining the accuracy of the score. [6] 

Method of Use

The GCS Assessment Aid has four steps to the assessment process: Check, observe, stimulate, rate. [7]

GCS Steps to Assessment

The assessor should evaluate each of the subscales as listed in the Assessment Aid. Each subscale has several components. Based on the level of consciousness, a score is assigned. A higher score indicates a greater level of consciousness.

GCS Subscales and Components

The GCS uses three sites for stimulation. This includes fingertip pressure, trapezius pinch and supraorbital notch. When stimulating these areas, health care practitioners should look for one of two responses: an abnormal flexion response or a normal flexion response. [7]

GCS Responses and Sites of Stimulation

The National Institute for Health Care and Excellence (NICE) published Clinical Guidelines on Head Injuries for Assessment and Early Management. NICE recommends the following Clinical Guidelines:

  • Until a patient has achieved a GCS Score of 15 on the GCS, patients should be observed every half hour.
  • Once the GCS Score has reached 15, the patient should be re-assessed using the GCS every half hour for two consecutive hours.
  • If the patient's GCS Score remains above 15, the patient should then be observed once every hour for four hours and then every 2 hours after that.
  • Note: If at any time a patient's GCS Score drops below 15, the healthcare practitioners should revert to observing the patient every half hour.[8]

The Institute of Neurological Sciences NHS Greater Glasgow and Clyde created a YouTube video to demonstrate how to properly use the outcome measure.




The inter-rater reliability of the total Glasgow Coma Scale is p = 0.86. Some research has subdivided the inter-rater reliability for each subscale. For the eye score the inter-rater reliability is p = 0.76, the verbal score is p = 0.67, and the motor score is p=0.81. [10] The research for test-retest reliability is not recent and should be updated, however, the best available evidence is k = 0.66 - 0.77. [11]

Based on a recent systematic review, the total score is typically less reliable than the individual components with a total Kappa value of 77% as compared to the eye, motor, and verbal scores which had Kappa values of 89%, 94%, and 88% respectively. [12]


The validity of the Glasgow Coma Scale comes under fire because a lot of hospitals administer the test while patients have been sedated, often underestimating patient scores. It’s also difficult to elicit accurate scores when patients are intubated. [13] Recent research has refuted that intubation elicits significantly different survival rates with the verbal score of r = 0.90 and the total score r = 0.97. [14] The motor score is consistently the most predictive component of the GCS. [15]


Given the current best available evidence, the GCS has a low sensitivity (56.1%) and a high specificity (82.2%). Therefore, there are very few false positives predicting a low rate of survival in healthy individuals. [16]

It is argued that the GCS does not accurately score patients who are intubated and does not assess brainstem reflexes, which may account for its low predictive capacity. A GCS administered at 24 hours post-injury has an odds ratio of 0.4 for predicting in-hospital mortality. When administered at 72 hours post-injury, the odds ratio improves to 0.59 for predicting in-hospital mortality. [17]

Evidence suggests that the Glasgow Coma Scale has a 71% accuracy in predicting functional independence post-injury. The GCS also modestly correlates with the Disability Rating Scale (-0.28) and the Cognitive component of the Functional Independence Measure (0.37). [18]



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