Glasgow Coma Scale (GCS)

Evidence Reviewed as of before: 29-09-2008
Author(s): Lisa Zeltzer, MSc OT
Editor(s): Nicol Korner-Bitensky, PhD OT; Elissa Sitcoff, BA BSc

Purpose

The Glasgow Coma Scale (GCS) was developed to describe the depth and duration of impaired consciousness or coma. In this measure, three aspects of behaviour are independently measured: motor responsiveness, verbal performance, and eye opening. The GCS can be used with individuals with traumatic brain injury, stroke, non-traumatic coma, cardiac arrest, and toxic ingestions.

In-Depth Review

Purpose of the measure

The Glasgow Coma Scale (GCS) was developed to describe the depth and duration of impaired consciousness or coma. In this measure, three aspects of behaviour are independently measured: motor responsiveness, verbal performance, and eye opening. The GCS can be used with individuals with traumatic brain injury, stroke, non-traumatic coma, cardiac arrest, and toxic ingestions.

Available versions

The GCS was published in 1974 by Graham Teasdale and Bryan J. Jennett. In 1976, Teasdale and Jennett distinguished between “normal” and “abnormal” flexion, which increased the “best motor response” item by one point.

Features of the measure

Items:

The GCS is comprised of three components: 1) Best eye response, which is believed to indicate whether the arousal mechanisms in the brainstem are active; 2) Best verbal response, which is believed to be the most common definition of the end of a coma, or the recovery of consciousness; and 3) Best motor response, which is thought to be associated with central nervous system functioning. Each component has a number of grades starting with the most severe. Best eye response has 4 grades; Best verbal response has 5 grades; Best motor response has 6 grades.

Best eye response (E)

  1. No eye opening
  2. Eye opening in response to pain (patient responds to pressure on the patient’s fingernail bed; if this does not elicit a response, supraorbital and sternal pressure or rub may be used).
  3. Eye opening to speech (not to be confused with an awaking of a sleeping person; such patients receive a score of 4, not 3).
  4. Eyes opening spontaneously

Best verbal response (V)

  1. No verbal response
  2. Incomprehensible sounds (moaning but no words).
  3. Inappropriate words (random or exclamatory articulated speech, but no conversational exchange).
  4. Confused (the patient responds to questions coherently but there is some disorientation and confusion).
  5. Oriented (patient responds coherently and appropriately to questions such as the patient’s name and age, where they are and why, the year, month, etc.).

Best motor response (M)

  1. No motor response
  2. Extension to pain (decerebrate response: rigid adduction and extension of the arms, legs stiffly extended, downward pointing of the toes, backward arching of the head, wrists pronated and fingers flexed).
  3. Flexion in response to pain (decorticate response: arms flexed, or bent inward on the chest, the hands are clenched into fists, and the legs extended).
  4. Withdraws from pain (pulls part of body away when pinched; normal flexion)
  5. Localizes to pain (purposeful movements towards changing painful stimuli; e.g. hand crosses mid-line and gets above clavicle when supra-orbital pressure applied).
  6. Obeys commands (the patient does simple things as asked).

Scoring:

In the GCS, each of the component scores as well as the sum of the components are considered. The total score is out of 15-points, with lower scores indicating more severe impairment. The lowest possible GCS total score is 3, indicating deep coma or death, and the highest possible score is 15, indicating a fully awake individual. The total score of the GCS is calculated by summing E + V + M.

The score is expressed in the form GCS (total score) = score on E + score on V + score on M. For example, GCS 9 = E2 V4 M3 indicates a total score of 9, a score of 2 on Best eye response (E), a score of 4 on Best verbal response (V), and a score of 3 on Best motor response (M). Note: For a patient who is intubated, the V is expressed as V intubated.

Interpretation of the GCS total score is as follows:

  • Minor head injury = 13-15
  • Moderate head injury = 9-12
  • Severe head injury (coma) = 8 or less

Time:

Not reported.

Subscales:

The GCS has 3 subscales: Best eye response, Best motor response, and Best verbal performance.

Equipment:

Only a pencil and the test are needed.

Training of administrator:

Although no training is required to administer the GCS, one study examined whether the GCS can be used reliably and accurately by inexperienced examiners and found that experienced medical personnel can use the measure with extremely high levels of accuracy and reliability, but inexperienced examiners may create significant errors, especially in the intermediate levels of consciousness, when the detection of neurologic changes is critical to patient monitoring (Rowley & Fielding, 1991). Thus, it is recommended that the inexperienced examiner be supervised by an expert when completing the GCS.

Alternative form of the GCS:

The GCS cannot be used with children, especially below the age of 36 months. This is due to the verbal performance component which is likely to be poor in even a healthy child. Thus, the Pediatric Glasgow Coma Scale (Reilly, Simpson, Sprod, & Thomas, 1988) was developed as an alternative to the GCS.

The Pediatric Glasgow Coma Scale can be obtained at the following website:

https://www.mdcalc.com/pediatric-glasgow-coma-scale-pgcs

Client suitability

Can be used with:

The GCS can be used with clients with stroke. However, the National Institutes of Health Stroke Scale (NIHSS), developed specifically for use with a stroke population may be a more useful assessment of consciousness in this population.

Should not be used with:

  • Clients with dysphasia, aphasia, and clients who are intubated will have a reduced score on the verbal response scale resulting in a reduced total GCS score but a normal level of consciousness. This should be taken into account when interpreting the GCS results in these individuals. Although it has been suggested that the verbal score be omitted in these clients, and an 8-level (3 to 10) modified GCS be used (Prasad, 1996; Prasad & Menon, 1998), the results of a larger study has suggested that the verbal subscale still be included because it adds important prognostic information (Weir, Bradford, & Lees, 2003).
  • In clients with hemiparesis, ensure that the motor scale is being applied to the less affected arm so that a “best” response can be obtained.
  • The GCS should be administered prior to administration of a sedative or paralytic agent, or after these drugs have been metabolized. Airway, breathing, and circulation should be assessed and stabilized prior to administering the GCS.

In what languages is the measure available?

The GCS has been translated into Chinese and is available online at the following
website: http://www.coma.ulg.ac.be/medical/acute.html

Summary

What does the tool measure? To describe the depth and duration of impaired consciousness or coma.
What types of clients can the tool be used for? The GCS can be used with individuals with traumatic brain injury, cerebrovascular events, nontraumatic coma, cardiac arrest, and toxic ingestions.
Is this a screening or assessment tool? Assessment
Time to administer Not reported.
Versions Pediatric Glasgow Coma Scale
Other Languages Chinese
Measurement Properties
Reliability
  • One study examined the internal consistency of the GCS and reported excellent internal consistency.
  • Two studies examined the inter-rater reliability of the GCS using kappa statistics. One study reported adequate inter-rater reliability and the other reported excellent inter-rater reliability for all three GCS subscales.
Validity

Criterion

Predictive validity:

Three studies examined the predictive validity of the GCS. One reported that the GCS adequately predicted stroke mortality. One study reported that the total GCS score predicted acute mortality with 87% accuracy using just the Best eye response and Best motor response subscales, and with 88% accuracy using all three subscales. One study
reported that the GCS was able to predict both 2-week mortality and 3-month recovery
from stroke.

Construct

Convergent validity:

One study examined the convergent validity of the GCS with the 60-Second Test (SST) and reported an excellent correlation using Spearman’s rho.

Floor/Ceiling Effects No studies have examined floor/ceiling effects of the GCS in patients with stroke.
Sensitivity/Specificity Not reported.
Does the tool detect change in patients?

One study examined the responsiveness of the GCS and reported that it had poor sensitivity to change.

Acceptability Caution should be used in interpreting the scores of intubated clients, or clients with dysphasia or aphasia.
Feasibility The GCS is a short measure that requires no additional equipment. Although training is not required, it is recommended as the measure is more reliable when completed by an experienced clinician. The scale is simple to score and cutoffs are well established in this measure.
How to obtain the tool? The GCS is available free online from the following website: http://www.strokecenter.org/professionals/stroke-diagnosis/stroke-assessment-scales/

Psychometric Properties

Overview

We conducted a literature search to identify all relevant publications on the psychometric properties of the GCS in individuals with stroke. We identified only three studies specifically examining the GCS in stroke (Weir et al., 2003; Prasad & Menon, 1998; Weingarten, Bolus, Riedinger, Maldonado, Stein, & Ellrodt, 1990). Thus, in this review we will present psychometric data from studies examining neurological patients that include patients with stroke.

Floor/Ceiling Effects

Not reported.

Reliability

Internal consistency:
Mayer, Dennis, Peery, Fitsimmons, Du, Bernardini, Commichau, et al. (2003) examined the internal consistency of the GCS in 171 patients in the neurointensive care unit. Cronbach’s alpha was found to be excellent (alpha = 0.83).

Test-retest:
Not reported.

Inter-rater:
Gill, Reiley, and Green (2004) examined the inter-rater reliability of the GCS in 116 emergency department patients with various diagnoses (10 clients with stroke, 9% of the sample). Two attending emergency physicians independently assessed the GCS within 5 minutes of each other while blinded to each other’s scores. Kappa statistics were calculated for each of the GCS subtests and the total score. Best eye response had adequate inter-rater reliability (weighted k = 0.72) as did Best verbal response (weighted k = 0.48) and Best motor response (weighted k = 0.40). The agreement percentage for total GCS was 32% (Kendall’s T-b = 0.74; Spearman rho = 0.86; Spearman rho2 = 75%). Agreement percentage for GCS Best eye response was 74% (T-b = 0.72; Spearman rho = 0.76; Spearman rho2 = 57%), verbal 55% (T-b = 0.59; Spearman rho = 0.67; Spearman rho2 = 44%), and motor 72% (T-b = 0.74; Spearman rho = 0.81; Spearman rho2 = 65%).

Mayer et al. (2003) examined the inter-rater reliability of the CGS in 64 patients in the neurointensive care unit. The GCS was administered by 2 or 3 examiners within 5 to 10 minutes of each other. Examiners were blinded to each other’s scores. Inter-rater reliability was excellent for the total GCS (weighted k = 0.91), Best visual response (weighted k = 0.86), Best motor response (weighted k = 0.91) and Best verbal response (weighted kappa = 0.76).

Validity

Content:

Not available.

Criterion:

Concurrent:
No gold standard exists against which to compare the GCS.

Predictive:
Weingarten et al. (1990) examined whether the GCS was as accurate in predicting stroke mortality as APACHE II (Knaus, Draper, Wagner, & Zimmerman, 1985), a scale that consists of the GCS score plus 11 other physiological variables, age, and a chronic health evaluation. 246 patients hospitalized with stroke, including 49 oversampled mortalities were included in the study. The GCS was found to adequately predict stroke mortality, and was found to be as accurate as the APACHE II score in predicting stroke mortality with the oversampled mortalities (r = -0.50 and r = 0.50, respectively) and after excluding the oversampled mortalities (r = -0.40 and r = 0.39, respectively).

Prasad and Menon (1998) compared the predictive accuracy of three alternative strategies for verbal scoring in 275 patients with acute stroke who were either intubated or had dysphasia. The total GCS score predicted acute mortality with 87% accuracy using just the Best eye response and Best motor response subscales, versus 88% accuracy with all three subscales. Thus, the authors concluded that the verbal subscale could be excluded from the total GCS score without loss of predictive value in clients with stroke.

Weir, Bradford, and Lees (2002) examined the ability of the GCS to predict 2-week mortality and 3-month recovery (survival, living at home) in a large cohort of individuals with acute stroke. The results of 1217 patients with stroke (including 349 patients with dysphagia) were analyzed. Area under the receiver operating curve (AUC) was used by the authors to compare versions of the GCS. The results of the AUC calculations indicated that the total GCS score had a greater AUC than the GCS without the verbal score for predicting 2-week mortality. This was apparent for all participants together (AUC = 0.78 for the total GCS score; 0.76 for the GCS without the verbal score) and for only the participants with dysphasia (AUC = 0.72 for total GCS score; 0.71 for the GCS without the verbal score). Similarly, the total GCS score was also better than the GCS without the verbal score for predicting 3-month recovery in all participants (AUC = 0.71 for the total GCS score; 0.67 for the GCS without the verbal score) and in participants with dysphasia only (AUC = 0.74 for the total GCS score; 0.70 for the GCS without the verbal score). These results suggest that in contrast to the findings by Prasad and Menon (1998), the verbal subscale should not be excluded in clients with dysphasia since it adds important prognostic information. These results also suggest that the total GCS score can predict early mortality and 3-month recovery and that the GCS better predicted the outcome of early mortality than the outcome of 3-month recovery.

Construct:

Convergent/Discriminant:
Mayer et al. (2003) examined the convergent validity of the GCS with the 60-Second Test (SST) in 171 patients in the neurointensive care unit using Spearman’s rho. The GCS and SST had an excellent correlation (Spearman’s rho = 0.72).

Known groups:
Not examined.

Responsiveness

Mayer et al. (2003) examined the responsiveness of the GCS in 36 patients in the neurointensive care unit. Patients underwent a baseline testing, followed by 1-13 follow-up encounters performed every 12-24 hours. The neurologist performed a brief standardized examination and provided a global clinical impression of change in level of consciousness (better, the same, or worse) compared with the prior encounter. According to the global impression of a neurologist, patients improved in 24% and worsened in 26% of the 187 follow-up examinations. Sensitivity of the GCS to these changes in level of consciousness was poor (46%).

References

  • Gill, M. R., Reiley, D. G., & Green, S. M. (2004). Interrater Reliability of Glasgow Coma Scale Scores in the Emergency Department. Ann Emerg Med, 43, 215-223.
  • Knaus, W. A., Draper, E. A., Wagner, D. P., & Zimmerman, J. E. (1985). APACHE II: A severity of disease classification system. Crit Care Med, 13, 818-829.
  • Lenfant, F., Sobraques, P., Nicolas, F., Combes, J. C., Honnart, D., Freysz, M. (1997). Use of Glasgow Coma Scale by anesthesia and intensive care internists in brain injured patients. Ann Fr Anesth Reanim, 16, 239-243.
  • Mayer, S. A., Dennis, L. J., Peery, S., Fitsimmons, B. -F., Bernardini, G. L., Commichau, C., Eldaief. (2003). Quantification of lethargy in the neuro-ICU: The 60-Second Test, Neurology, 61(4), 543-545.
  • Prasad, K. (1996). The Glasgow Coma Scale: A critical appraisal of its clinimetric properties. Journal of Clinical Epidemiology, 49(7), 755-763.
  • Prasad, K. & Menon, G. R. (1998). Comparison of three strategies of verbal scoring of the Glasgow Coma Scale in patients with stroke. Cerebrovasc Dis, 8, 79-85.
  • Reilly, P., Simpson, D., Sprod, R., Thomas, L. (1988). Assessing the conscious level in infants and young children: A paediatric version of the Glasgow Coma Scale.Child’s Nerv Syst, 4(1), 30-33.
  • Rowley, G, Fielding, R. (1991). Reliability and accuracy of the Glasgow Coma Scale with experienced and inexperienced users. Lancet, 337, 535-538.
  • Teasdale, G., Jennett, B. (1974). Assessment of coma and impaired consciousness. A practical scale. The Lancet, 2(7872), 81-84.
  • Teasdale, G. M., & Jennett, B. (1976). Assessment and prognosis of coma after head injury. Acta Neurochir (Wien), 34, 45-55.
  • Warlow, C. P., Dennis, M. S., van Gijn, D., Hankey, G. J., Sandercock, P., Bamford, J. M., et al. (2001). Stroke: A Practical Guide to Management (2nd ed.). Malden, MA: Blackwell Publishing.
  • Weir, C. J., Bradford, A. P., & Lees, K. R. (2003). The prognostic value of the components of the Glasgow Coma Scale following acute stroke. Q J Med, 96, 67-74.

See The Measure

How to obtain the GCS:

The GCS is available at the following website:
http://www.strokecenter.org/trials/scales/glasgow_coma.html

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