Frequently Asked Questions
- What factors can interfere with assessment of the Glasgow Coma Scale and what can be done about them?
- How is the Glasgow Coma Scale modified for Children?
- What is the reliability of the Scale? How is it optimised?
- Is the Glasgow Coma Scale only for use in Head Injuries?
- When and how often should Observations be recorded?
- How much change is important?
- What are the relationships and roles of the Coma Scale and the Coma Score?
- What are the key references to development and use of Glasgow Coma Scale?
1. What factors can interfere with assessment of the Glasgow Coma Scale and what can be done about them?
There are three main sources of possible interference with assessment of one or more component of the scale.
- Pre-existing factors
- Language or cultural differences
- Intellectual or neurological deficit
- Hearing loss or speech impediment
Effects of current treatment
- Physical e.g. intubation or tracheostomy
- Pharmacological e.g. sedation or paralysis
Effects of other injuries or lesions
- Orbital/Cranial fracture
- Dysphasia or Hemiplegia
- Spinal cord damage
Actions to avoid loss of Information
- Communication Barriers:
Adapt the method of interaction to the patient, for example by choice of language, culturally appropriate examining person, or using written communication.
- Treatment influences
In the context of endotracheal intubation or tracheostomy, the verbal component of the score can be denoted as ‘not testable,’ NT. The motor and eye components can still be assessed and the trend will still be useful*.
For pharmacological impairment, temporarily reverse sedation and paralysis (wake up test)
- Other injuries
Adapt the examination technique for patients with spinal cord injury, for example by focusing on tongue and eye movements instead of hand movements
Correction of systemic hypoxia and hypertension will optimise the patient’s brain function.
*Dealing with missing information
There are various different strategies for dealing with information that is missing because of factors interfering with assessment such as those described above.
- Assess, communicate and make decisions using the remaining components. Although guidelines are often expressed in terms of a total GCS ‘score,’ the trend in whichever of the components (eye, motor or verbal) can be assessed is still valuable.
- Do not use number ‘1’ to record missing component; use ‘NT’ (Not testable).
- Do not report a total score when a component is Not Testable because the score will be low and this could be confusing to medical colleagues. This may also imply that the patient is more unwell than they actually are.
- It is possible using statistical methods to estimate a missing component from the findings in the other components. This is probably more relevant to research than clinical practice.
Meredith W, Rutledge R, Fakhry SM, Emery S, Kromhout-Schiro S. The conundrum of the Glasgow Coma Scale in intubated patients: a linear regression prediction of the Glasgow verbal score from the Glasgow eye and motor scores. J Trauma. 1998; 44:839-44; discussion 844-5.
2. How is the Glasgow Coma Scale modified for Children?
The scale can be applied without modification to children over 5 years old. In younger children and infants, an assessment of a verbal response as “orientated” and motor response as “obeys commands” is usually not possible. A ‘Paediatric Glasgow Coma Scale’ was therefore described in Adelaide in which responses were modified as below.
|Eye Opening||Verbal Response||Best Motor Response|
|Spontaneous||Talks normally||Obeys commands|
|To sound||Words||Localises pain|
|To pain||Vocal sounds||Flexion to pain|
|None||Cries||Extension to pain|
Although several other systems have been put forward, none has gained greater widespread acceptance. The findings on the Adelaide scale can be related to normal child development of response and to the total score to be anticipated at increasing ages.
|6 months||Vocal sounds||10|
Simpson D Reilly P. Pediatric coma Scale. Lancet. 1982;450
Reilly PL, Simpson DA. Sprod R. Thomas L. Assessing the conscious level in infants and young children: a paediatric version of the Glasgow Coma Scale.Childs Nervous System. 4(1):30-3, 1988
Simpson DA. Cockington RA. Hanieh A. Raftos J. Reilly PL. Head injuries in infants and young children: the value of the Paediatric Coma Scale. Review of literature and report on a study.Childs Nervous System. 7(4):183-90, 1991
3. What is the reliability of the Glasgow Coma Scale? How is it optimised?
In the absence of a ‘gold standard’ for consciousness, evaluation of the Scale’s validity as an indicator of severity was progressively built up from research into the relationships of its findings with other early clinical, functional metabolic and structural features and with late outcome.
There is not a single, overall figure for the reliability of assessment using the Glasgow Coma Scale. This is because there are wide variations in the findings in reported studies. In research performed during development of the Glasgow Coma Scale its reliability was shown to be better than for other systems in use at the time and approached that of examination of pupil reaction1. Since then various different studies have reported the reliability as high2 and low3.
The reliability of a scaling method is usually expressed as its Kappa statistic, for which 1 = perfect agreement and 0 = agreement no better than expected by chance. A formal literature review found values reported for the Glasgow Coma Scale to range from 0.85 to 0.32. A factor often found to reduce reliability is variation in the way that missing information is dealt with.
Factors shown to enhance reliability include the extent of training and experience of the examiner. This is why the video on glasgowcomascale.org aims to promote reliability through the provision of a guide to the structured assessment of the scale. This new structured approach, based on defined criteria including dealing with missing data, should improve on the current approach to allocation of ratings by subjective comparison against typical responses.
- Teasdale G, Knill-Jones R, van der Sande J. Observer variability in assessing impaired consciousness and coma. J Neurol Neurosurg Psychiatry 1978;41:603-10.
- Heard K, Bebarta VS. Reliability of Glasgow Coma Scale for emergency department evaluation of poisoned patients. Hum Exp Toxicol. 2004; 23:197-200.
- Gill M, Reilley DG, Green SM. Interrater reliability of Glasgow Coma Scale Scores in the Emergency Department. Ann Emerg Med. 2004; 43:215-23..
- Baker M. Reviewing the application of the Glasgow Coma Scale: Does it have interrater reliability? Brit J of Neuroscience Nursing 2008; 4:342 – 47
4. Is the Glasgow Coma Scale only for use in Head Injuries?
The Glasgow Coma Scale can be applied to describe impairment of consciousness from any cause. It has found most use in head injuries, but reports of its application in impaired consciousness from other aetiologies are indicated below. In conditions where the damage is predominantly focal, as in a stroke, additional information from assessment of the degree of any focal deficit is clearly important.
Spontaneous subrachnoid haemorrhage
Teasdale GM, Drake CG, Hunt W, et al. A universal subarachnoid hemorrhage scale: report of a committee of the World Federation of Neurosurgical Societies. J Neurol Neurosurg Psychiatry. 1988; 51:1457
Spontaneous intracerebral haemorrhage
J. Claude Hemphill III,David C. Bonovich, Lavrentios Besmertis, Geoffrey T. Manley, S. Claiborne Johnston. The ICH Score A Simple, Reliable Grading Scale for Intracerebral Hemorrhage Stroke. 2001;32: 891-897
C J Wier, A P J Bradford,K R Lees Ischaemic stroke The prognostic value of the components of the Glasgow Coma Scale following acute stroke Quarterly Journal of Medicine (2003) 96 (1): 67-74
Intracranial Infection and brain abscess
A prospective study of glasgow coma scale (GCS), age, CSF-neutrophil count, and CSF-protein and glucose levels as prognostic indicators in 100 adult patients with meningitis. C.-M. Schutte, C.H. van der Meyden. Journal of Infection 1998, Pages 112–115
Brain abscess in 142 patients: factors influencing outcome and mortality. Jen-Ho Tseng, Ming-Yuan Tseng. Surgical Neurology, 2006, Pages 557–562
Early Physiologic Predictors of Injury Severity and Death in Blunt Multiple Trauma John H. Siegel, MD; Avraham I. Rivkind, MD; Samir Dalal, MD; Shirin Goodarzi, MS Arch Surg. 1990;125(4):498-508
Gennarelli TA, Champion HR, Copes WS, Sacco WJ. Comparison of mortality, morbidity, and severity of 59,713 head injured patients with 114,447 patients with extracranial injuries. J Trauma. 1994; 37:962-8
Non traumatic coma
Nontraumatic Coma: Glasgow Coma Score and Coma Etiology as Predictors of 2-Week Outcome. Ralph L. Sacco, MD; R. VanGool, MD; J. P. Mohr, MD; W. A. Hauser, MD. Arch Neurol. 1990;47(11):1181-1184.
Comparison of APACHE II, MEES and Glasgow Coma Scale in patients with nontraumatic coma for prediction of mortalityŠtefek Grmec* and Vladimir Gašparovic† Critical Care 2001, 5:19–23
Reliability of the Glasgow Coma Scale for the emergency department evaluation of poisoned patients. K Heard, VS Bebarta - Human & experimental toxicology, 2004 197-200
5. When and how often should Observations be recorded?
The timing and frequency of assessment that are appropriate varies according to the stage after onset of the impairment of consciousness and the pattern in any previous observations of a patient. Observation should begin as soon as possible after onset of the impaired consciousness in order to guide initial management and to establish a baseline against which to interpret later findings. Observations initially should be repeated frequently to establish if the patient is stable or to detect any trends of improvement, or of deterioration from developing complications. When a stable pattern emerges as time passes, the frequency can be reduced.
Specific criteria for patients with an acute head injury have been suggested by NICE :
|Frequency of observation||Observations should be performed and recorded on a half hourly basis until GCS equal to 15 has been achieved. If GCS=15 observe: half-hourly for 2 hours, then 1 hourly for 4 hours, then 2 hourly thereafter; Should the patient with GCS equal to 15 deteriorate at any time after the initial 2-hour period, observations should revert to half-hourly.|
|Urgent reappraisal by the supervising doctor||
A sustained (that is, for at least 30 minutes) drop of one point in GCS level (greater weight should be given to a drop of one point in the motor score of the GCS);
Any drop of 3 or more points in the eye-opening or verbal response scores of the GCS or 2 or more points in the motor response.
- NICE : National Institute of Clinical Excellence Clinical Guideline 176 Head Injury :Triage, Assessment, investigation and early management of head injury in children, young people and adults. 2014
6. How much change is important?
Rigid criteria for what changes should prompt actions are not appropriate; circumstances vary widely and the role of the scale is to support not replace clinical decision-making. Nevertheless, some factors can provide guidance.
If responsiveness reduces, the features to take into account in deciding action include:
- The pattern of responsiveness before the change: the more stable the pattern, the more a change may be important
- The level of responsiveness before the change: the lower the preceding responsiveness the sooner action is appropriate.
- The aspect of the scale that has changed and the extent of the change: motor changes usually call for a response sooner than changes to the eye or verbal components.
- If the change persists when assessment is repeated, including confirmation by a colleague if doubt remains, then the change is more likely to be significant.
7. What are the relationships and roles of the Coma Scale and the Coma Score?
The core concept in the Scale is that the patient is described in simple, objective terms in order convey a clear unambiguous picture of their responsiveness. This remains the proper approach in the care of an individual patient.
The Score was a later development and is actually best suited to summarising information about groups of patients. The allocation of numbers to the steps in the three responses was introduced as a device to facilitate entry of clinical findings into a databank. Each step in the eye, verbal and motor subscales was assigned a number, the worse the response the lower the number, and recorded separately eg as E=1 V=1 M=1 Aggregating the separate ‘scores’ into a single ‘total’ score was soon taken up as a way to summarise a patients responsiveness and to present findings in groups of patients. The numbering of the best levels in each component is E=4, V=5, M=6 and so the best total =15 and the lowest =3.
The Score is popular as a ‘shorthand’ way of communicating the severity of a patient’s condition, but it has limitations. It is less informative than the full description of the three components of the Scale. Moreover, if one of these components is not testable then a valid total cannot be calculated.
8. What are the key references to development and use of the Glasgow Coma Scale?
The key references can be found here.