Glasgow Coma Scale (GCS)

Reviewed and revised 12 October 2019

OVERVIEW

• The GCS is a neurological scoring system used to assess conscious level after head injury
• Teasdale and Jennet invented the GCS in 1974
• It is now usually scored out of 15 and is comprised of 3 categories, best eye response, best vocal response and best motor response (e.g. E4V5M6 = GCS15)

CALCULATION OF GCS

Eye response (E)

1. No eye opening
2. Eye opening in response to pain stimulus (a peripheral pain stimulus, such as squeezing the lunula area of the patient’s fingernail is more effective than a central stimulus such as a trapezius squeeze, due to a grimacing effect)
3. Eye opening to speech (not to be confused with the awakening of a sleeping person; such patients receive a score of 4, not 3)
4. Eyes opening spontaneously

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)

Motor response (M)

1. No motor response
2. Extension to pain (extensor posturing: abduction of arm, external rotation of shoulder, supination of forearm, extension of wrist, decerebrate response)
3. Abnormal flexion to pain (flexor posturing: adduction of arm, internal rotation of shoulder, pronation of forearm, flexion of wrist, decorticate response)
4. Flexion/Withdrawal to pain (flexion of elbow, supination of forearm, flexion of wrist when supra-orbital pressure applied ; pulls part of body away when nailbed pinched)
5. Localizes to pain (Purposeful movements towards 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, e.g. stick out tongue or move toes)

USES

• categorises severity of TBI into mild (13-15), moderate (9-12) and severe (8 or less)
• used in BTF guidelines as part of the indications for ICP monitoring (e.g. GCS 8 or less and abnormal CT head)
• used for determining the need for CT head in TBI by validated tools such as the Canadian CT Head Rule
• Traditional ATLS mantra is “GCS 8, intubate”
• used in APACHE II
• originally described for monitoring depth of coma over time in a neurosurgical unit (never validated)

ADVANTAGES

• most widely recognised of all conscious level scoring systems in the world
• has face validity (looks like it should work)
• quick
• reproducible (this is controversial, in one study 38% of the cases the GCS scores were the same and in 33% of cases the scores varied with more than two points)
• skewed towards motor score, which is good since this is the most reliable measure of short-term prognosis in TBI
• the distinction between a motor score of 2, 3 and 4 is a very useful clinical indicator of the severity of TBI, and the area of brain function that has been affected
• correlates with adverse neurological outcomes such as brain injury, neurosurgical intervention, and mortality

DISADVANTAGES

Problems with the use of GCS

• not originally intended to be converted into a single score — the components (E4,V5, M6) are more important than the total score
• does not incorporate brain-stem reflexes
• M score does not factor in unilateral pathology
• unreliable in patients in the middle range of 9-12
• The same GCS score will predict different TBI mortality depending on the components
  — GCS of 4 with the components 1+1+2 (E+V+M) predicts a mortality rate of 48%
  — GCS of 4 with the components 2+1+1 (E+V+M) predicts a mortality rate of 19%
• grossly predictive but cannot accurately predict outcomes in individual patients (on par with weather presenters predicting rain or WBC predicting appendicitis!)

Problems with performing GCS

• designed as a tool for repeated bedside assessment of various neurological functions in patients in a neurosurgical ward, not for use in TBI
• It is difficult for untrained staff to apply properly, especially distinguishing between M= 3,4,5 (even neurosurgeons get it wrong ~50% of the time)
• Variation in scoring V in intubated patients
• subject to language barriers
• cannot be applied to small children
• may be affected by other factors influencing level of consciousness, e.g. drugs such as alcohol and sedatives
• GCS is often used in settings such as toxicology where it is unvalidated
• Debates within the literature as to when GCS can be first applied after TBI, i.e when is the first post-resuscitation GCS applicable

Problems with accuracy and validity of GCS

• Controversy in the literature
• There is poor inter-observer reliability
• Reproducibility is poor (only 50% in neurosurgeons!)
• There is little evidence demonstrating validity and reliability of the GCS
• Not proven to be better than unstructured clinical judgement
• There are numerous other neurological scoring systems that have demonstrated similar or greater validity and reliability e.g. the FOUR score, AVPU in children
• GCS 8 does not reliably correlate with the presence or absence of airway reflexes

‘We have never recommended using the GCS alone, either as a means of monitoring coma, or to assess the severity of brain damage or predict outcome.’

Teasdale and Jennet in 1978

ALTERNATIVES

• FOUR score
• AVPU
• Simplified Motor Score (aka TROLL: Test Responsiveness: Obeys, Localizes, or Less)
• unstructured clinical judgement

MY APPROACH

• Due to widespread adoption I still use GCS in TBI in conjunction with other clinical information and investigations in the assessment of TBI severity, to guide monitoring and management and as an aid to prognostication
• However, because of its limitations, GCS must be used cautiously
• all staff need to be aware of the same criteria for its use and application and have a standardised approach to its assessment
• on-going education is needed to make sure that it is used correctly

VIDEOS

Videos by Jake Timothy (Consultant Neurosurgeon) and Sir Graham Teasdale (professor of Neurosurgery) on the history and use of GCS:

References and Links

Journal articles

• Chou R et al. Predictive Utility of the Total Glasgow Coma Scale Versus the Motor Component of the Glasgow Coma Scale for Identification of Patients With Serious Traumatic Injuries. Ann Emerg Med. 2017 Aug;70(2):143-157 [PMID 28089112]
• Green SM. Cheerio, laddie! Bidding farewell to the Glasgow Coma Scale. Ann Emerg Med. 2011 Nov;58(5):427-30. PMID: 21803447.
• Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974 Jul 13;2(7872):81-4. PMID: 4136544.
• Teasdale G, Jennett B, Murray L, Murray G. Glasgow coma scale: to sum or not to sum. Lancet. 1983 Sep 17;2(8351):678 PMID: 6136811.
• Zuercher M, Ummenhofer W, Baltussen A, Walder B. The use of Glasgow Coma Scale in injury assessment: a critical review. Brain Inj. 2009 May;23(5):371-84. PMID: 19408162.

FOAM and web resources

• Glasgow Coma Scale website
• ScanCrit — Why the Glasgow Coma Scale has got to go (2011)