Glasgow Coma Scale

Function

Scoring and Parameters

The Glasgow Coma Scale divides into three parameters: best eye response (E), best verbal response (V) and best motor response (M). The levels of response in the components of the Glasgow Coma Scale are ‘scored’ from 1, for no response, up to normal values of 4 (Eye-opening response) 5 ( Verbal response) and 6 (Motor response)

The total Coma Score thus has values between three and 15, three being the worst and 15 being the highest. 

The score is the sum of the scores as well as the individual elements. For example, a score of 10 might be expressed as GCS10 = E3V4M3.

Best eye response (4)

1. No eye opening
2. Eye opening to pain
3. Eye opening to sound
4. Eyes open spontaneously

Best verbal response (5)

1. No verbal response
2. Incomprehensible sounds
3. Inappropriate words
4. Confused
5. Orientated

Best motor response (6)

1. No motor response.
2. Abnormal extension to pain 
3. Abnormal flexion to pain 
4. Withdrawal from pain
5. Localizing pain
6. Obeys commands

Application of the Glasgow Coma Scale in Pediatrics

The Glasgow Coma Scale can be used in children older than 5 years with no modification. Younger children and infants are not able to provide the necessary verbal responses for the practitioner to use the scale to assess their orientation or obey the commands to evaluate their motor response. Since a Pediatric Glasgow Coma Scale was initially described in Adelaide, there have been several modifications without any particular one becoming universally accepted.[7] The versions below derive from those  of James and the  Pediatric Emergency Care Applied Research Network[8][6]

Children less than 2 years old (pre-verbal) / Children greater than 2 years old (verbal)                        

Best eye response

1. No eye opening / 1 No eye opening                                           
2. Eye opening to pain / 2 Eye opening to pain
3. Eye opening to sound / 3  Eye opening to sound
4. Eyes open spontaneously / 4 Eyes open spontaneously

Best verbal response                           

1. None / 1 None
2. Moans in response to pain / 2 Incomprehensible sounds
3. Cries in response  to pain / 3 Incomprehensible words
4. Irritable/cries / 4  Confused 
5. Coos and babbles / 5 Orientated - appropriate

Best motor response 

1. No motor response / 1 No motor response.
2.  Abnormal extension to pain / 2 Abnormal extension to pain 
3. Abnormal flexion to pain / 3  Abnormal flexion to pain 
4. Withdrawal to pain / 4 Withdrawal to pain
5.  Withdraws to touch / 5 Localises to pain
6. Moves spontaneously and purposefully / 6 Obeys commands

Issues of Concern

The following factors may interfere with the Glasgow Coma Scale assessment:

1. Pre-existing factors
• Language barriers
• Intellectual or neurological deficit
• Hearing loss or speech impediment
2. Effects of current treatment
• Physical (e.g., intubation): If a patient is intubated and unable to speak, they are evaluated only on the motor and eye-opening response and the suffix T is added to their score to indicate intubation.
• Pharmacological (e.g., sedation) or paralysis: If possible, the clinician should obtain the score before sedating the patient.
3. Effects of other injuries or lesions
• Orbital/cranial fracture
• Spinal cord damage
• Hypoxic-ischemic encephalopathy after cold exposure

There are instances when the Glasgow Coma Scale is unobtainable despite efforts to overcome the issues listed above. It is essential that the total score is not reported without testing and including all of the components because the score will be low and could cause confusion.

Clinical Significance

Assessment of responsiveness with the Glasgow Coma Scale is widely used to guide early management of patients with a head injury or other kind of acute brain injury. Decisions in more severely impaired patients include emergent management such as securing the airway and triage to determine patient transfer. Decisions in less severely impaired patients include the need for neuroimaging, admission for observation or discharge. Serial Glasgow Coma Scale assessments are also critical in monitoring the clinical course of a patient and guiding changes in management.

The information gained from the three components of the Scale varies across the spectrum of responsiveness [9]. ( Figure 1 ) Changes in motor response are the predominant factor in more severely impaired patients, whereas eye and verbal are more useful in lesser degrees.  In individual patients, the clinical findings in three components should, therefore, be reported separately. The total score communicates a useful summary overall index but with some loss of information.

In both preverbal and verbal pediatric patients, the Glasgow Coma Scale is an accurate marker for clinically important traumatic brain injury (i.e., injury requiring neurosurgical intervention, intubation for over 24 hours, hospitalization for more than two nights, or causing death.[6]

The Glasgow Coma Scale has been taken into numerous guidelines and assessment scores. These include trauma guidelines (such as Advanced Trauma Life Support), Brain Trauma Foundation (severe TBI guidelines), intensive care scoring systems (APACHE II, SOFA) and Advanced Cardiac Life Support.

Relation to Outcome

A relationship between assessments of the GCS (typically reported as the total GCS Score) and the outcome was shown clearly by  Gennarelli et al.,[10] who demonstrated the existence of a continuous, progressive association between increasing mortality after a head injury and decreases in GCS Score from 15 to 3( Figure2). This association has been seen in many other subsequent studies. The findings for the eye, verbal and motor responses also relate to the outcome but in distinctive ways so that assessment of each separately yields more information than the aggregate total score.[9]

However, although it is one of the most powerful clinical prognostic features, neither the GCS score nor any single feature alone should be used to predict an individual patient’s outcome. This is because the prognostic implications of the score are influenced by several factors. These include the diagnosis, and in trauma the cause and if there are extracranial injuries,[11] patient-related factors such as age and other clinical indices (such as pupillary dysfunction and imaging findings), the GCS score is a key component of multifactorial models for prediction of outcomes such as in the IMPACT and CRASH trials.[11][12]                                             

Glasgow Coma Scale Pupils Score

The Glasgow Coma Scale Pupils Score (GCS-P) was described by Paul Brennan, Gordon Murray, and Graham Teasdale in 2018 as a strategy to combine the two key indicators of the severity of traumatic brain injury into a single simple index.[13][14]

Calculation of the GCS-P is by subtracting the Pupil Reactivity Score (PRS) from the Glasgow Coma Scale (GCS) total score:

• GCS-P = GCS – PRS

The Pupil Reactivity Score is calculated as follows.

Pupils unreactive to light - Pupil Reactivity Score

• Both pupils - 2
• One pupil - 1
• Neither pupil - 0

The GCS-P score can range from 1 and 15 and extends the range over which early severity can be shown to relate to outcomes of either mortality or independent recovery.

Classification of Severity of TBI

The relationship between the GCS Score and outcome l is the basis for a common classification of acute traumatic brain injury:

• Severe, GCS 3 to 8
• Moderate, GCS 9 to 12
• Mild, GCS 13 to 15

With the GCS-P score values between one and 8 denote a severe injury.

Other Issues

The reliability of the GCS Scale has undergone extensive study.   Although its reproducibility has been questioned in a small number of reports, these have proved to be exceptions. Thus, a systematic review of all 53 published reports in 2016 concluded that 85% of the findings in higher quality studies showed substantial reliability as judged by the standard criterion of a kappa statistic (k) above 0.6 [15].  The reproducibility of the total GCS Score was also high with kappa greater than 0.6 in 77 % of observations. A clear beneficial effect on reliability resulted from education and training. To promote this initiative, a standardized structured approach to assessment has been set out (Teasdale GM et al. Nursing Times. 2014. 110:  12-16.).

Alternatives to the GCS Scale have been described. These typically have been derived either by shortening components of the scale or by adding extra features.  The Simplified Motor Scale recognizes only three levels of motor response; this may be sufficient to support binary decisions, for example about intubation, in prehospital care and emergency room but it has no advantage over the GCS Score in identifying early mortality.[15][16] Such contracted scales inevitably convey less information and cannot match the discrimination provided by the GCS or GCS-P score in stratifying patients across the full spectrum of early severity, in monitoring changes during care in the individual or in relating to the prognosis for different late outcomes.

More complex scales include the "Full Outline Of Unresponsiveness" or FOUR developed in neurological intensive care.[17] In addition to eye and motor responses derived from GCS, FOUR incorporates two additional,  brain stem and respiratory, components. These additional features have been found to have lesser relations to with outcome than the eye and motor scales. The ‘brain stem’ feature has as its basis the observations of pupils, corneal, and cough responses. The value of assessing pupil reactivity is well established, but the additional contribution of the other features is not clear.  The basis of the respiratory subscale is the rhythm of breathing, but the reliability of the feature is unclear; the pattern of breathing can be variable, is influenced by extracranial factors, by sedation and by the technique of ventilation. 

A systematic review has not been reported on comparisons between the reliability and prognostic yield of the Four Score and the GCS Score. Nevertheless, most studies have not shown a significant difference,[18] and the addition to the GCS of information about pupil response will increase its performance relative to the FOUR score.[16]

The Glasgow Coma Scale - PA charts combine the prognostic information from the GCS, the pupil response, imaging findings and the patient’s age in a simple visual way that is easy to understand.[17] They provide a user-friendly predictive tool that balances between the simplicity but limited information in a ‘score’ and the more precise but more complex calculations of multivariate models.

Enhancing Healthcare Team Outcomes

All healthcare workers should know about the GCS and what the numbers mean. Anytime the GCS is initially performed, the numbers should be recorded in the medical chart so that the patient can undergo serial monitoring.