Surgical Technique
Glasgow Coma Scale: Technique and Intepretation
Bhaskar S*
Department of Neurosurgery, PGIMER & Dr RML Hospital, India
*Corresponding author: Bhaskar S, Department of Neurosurgery, PGIMER & Dr RML Hospital, New Delhi-110001, India
Published: 03 Aug, 2017
Cite this article as: Bhaskar S. Glasgow Coma Scale:
Technique and Intepretation. Clin Surg.
2017; 2: 1575.
Abstract
The Glasgow Coma Scale (GCS) was designed to objectively, easily, methodically evaluate the
neurological status of patients with impaired consciousness especially after traumatic brain injury.
The score is used to grade and plan treatment of patients with head injury. It can also be used to
monitor neurological status of critically ill patients.
There are three parameters used- eye opening, verbal response and best motor response with the
score ranging from 3-15. The technique, interpretation and certain practical issues concerning the
GCS are discussed.
Keywords: Glasgow coma scale; Head injury; Interpretation
Introduction
The Glasgow Coma Scale was introduced in 1974 [1]. The acronym stands for both Glasgow Coma Scale (individual components) and Score (total). The scale is used to decide the management issues of individual patients. The total is used to group patients into various categories so that management protocols can be designed and outcome measured. It has three components for assessment that are totalled and a combined score is given. The total score is used in classifying head injuries into mild (3-8), moderate (9-12) and severe (13-15) [2]. The GCS has made a subjective assessment of head injury (coma, semi coma, drowsy, stupor, altered sensorium, locked in state) into an objective method [3,4]. It has significant advantages and also certain drawbacks that need to be understood when applying it. The basic techniques of how to perform the GCS and the issues involved in its interpretation are discussed.
Technique
Key Messages (Provide appropriate messages of about 35-50 words to be printed in centre box).
There are three parameters that are assessed
Eye opening (E): used as a reflection of the intensity of impairment of activating functions.
Verbal response (V): Index of higher cortical function.
Best motor response (M): Knowing the integrity of the nervous system in patients who are not
speaking.
The original score had total score of 14, which was increased to 15 (Table 1).
GCS assessment method [5,6]
Check: To check for any factors that might interfere with the assessment like sedation, muscle
relaxants, metabolic disturbances, fever, hemodynamic disturbances, eye swelling, airway injuries,
limb injuries, intoxicants
Observe: To see for spontaneous patient actions (eg: eye opening).
Stimulate: Once it is decided that there is no spontaneous response then to stimulate and check
for responses.
Rate: After the stimulation for various parameters the score is recorded and totalled to arrive
at the GCS score.
Eye opening
E4 (Spontaneous): The patient will be opening his/her eyes without any external stimulus and
this indicates that arousal mechanisms in the brainstem are intact. In the rare case of persistent
vegetative state the patient will have a spontaneous opening without awareness.
E3 (Eye opening to command): Next a verbal stimulus is given;
this includes any loud sound that will make the patient open eyes and
not necessarily a command to open eyes. The sound should be loud
enough to evoke a response.
E2 (Eye opening to pain): The painful stimulus is given at either
the nail bed with a pen/pencil or pinching the trapezius muscle
or rubbing the sternum. The sternal region has just skin over the
periosteum and hence is very sensitive. The stimulus has to be a
firm rubbing movement and not excessive downward force that
may fracture ribs or even the sternum in undiagnosed chest wall
injuries. The stimulus is sustained for 10 seconds (if required) before
concluding that there is no response to pain.
E1 (None): No Eye Opening to even painful stimulus: Patient
might have closed the eyes as a result of the stress due to the trauma or
at times even sleeping after the exhaustion following the event! So one
should not give a painful stimulus before a verbal one. Pressing over
the supraorbital notch is not recommended for eye opening as it may
elicit an erroneous response by a grimace reflex. The body’s natural
reflex to any painful stimulus in the facial region is to close eye and
protect them from that stimulus! Another issue to be noted is to make
sure that there are no facial injuries that might exacerbate by applying
a stimulus in the facial region. If there is extensive periorbital swelling
that precludes eye opening then it can be written as Not Assessed or
Ep or Eedema. Whatever is the format it should be uniformly followed by
all caregivers in a given institution? Any confusion, then it should be
explicitly communicated as to what state the patient is in. This would
avoid any confusion in assessment and subsequent management.
Verbal response
V5 (Oriented): Patient is asked who, where and what time (at
least in terms of year, month and day of the week) if the response to all
three questions are correct then it is V6. The thing to be remembered
is some patients are not told that they have been admitted to that
particular hospital, so if they tell the name of some other health
centre then it should be corroborated with the relatives about the
correctness. It might be the case that the patient was taken to that
centre before being shifted to the current place of evaluation! If the
patient only answers some of these questions and not all correctly
then can be sub categorized into sub groups based on the number
answered correctly. This will only be useful for research purposes and
should not influence management decisions.
V4 (Confused): Patient does engage in conversation that includes
appropriate sentences and words but is not answering appropriately
the above three questions.
V3 (Inappropriate Speech): Here it is a few exclamatory words
(more often swearing) and does not result in sustained conversation.
V2 (Incomprehensible sounds): The patient moans and groans,
most often to painful stimulus.
V1 (Absent): No verbal response.
The patient who is intubated or tracheostomized cannot be
assessed for an appropriate verbal response. Patients with focal
damage to speech areas (eg: Broca area) can have an impaired speech
response but may otherwise be alert.
Many centres give a score of 1 in the verbal response to patients
whose airway is secured by a definitive airway. All caregivers in that
institution should uniformly apply this. Otherwise it will create an
error in the evaluation. For example if a patient has been intubated for
a faciomaxillary injury (eg mandibular fracture) that is compromising
the airway, the GCS will be E4V1M6. This becomes moderate
head injury whereas it might not be so. It is advisable to use the
abbreviation of VET or VT to denote an intubated or tracheostomized
patient respectively. This way the confusion stated in the previous
scenario would be avoided. This drawback with the GCS has become
more in the recent times as the intubation and ventilation care has
significantly increased.
Best Motor response
The motor response becomes very important in a person who is
not conversing or at least is at a confused level.
M6 (Obeying commands): This is tested by asking the patient to
move fingers, wriggle toes, show tongue/open or close eyes (especially
in suspected spinal injury). This response ensures that there is an intact
arc of receiving stimulus (command), processing at the cortical level
and executing via motor function (response). The stimulus should be
loud and clear before inferring lack of response and proceeding to
painful stimulus. One should remember that some motor response
might be elicited by simple grasp reflex, startle response or even to
postural changes. These should not be interpreted as M6. If in doubt
then specificity of the response should be crosschecked eg: ask to
release hand in case of suspected grasp reflex, holding limbs to verbal
command. Once it is decided that the patient does not respond to
verbal command then a painful stimulus is given in a standardized
manner and maintained for appropriate time to see for motor
response. The sites for a painful stimulus are- pinch the trapezius,
firm rubbing movement (not pressing) over the sternum or press over
the supra-orbital notch. These stimuli are sustained for a period of
10 seconds to make sure that the stimulus is adequate. The nail bed
stimulus is not applied in this situation because the other upper limb
has to reach over and localize plus it will be erroneous in case of focal
brain injuries and spinal cord injuries.
M5 (Localizing to painful stimulus): This response will be when
the hand reaches the site of stimulus i.e. the sternum or trapezius. In
the case of the supra-orbital area the patient’s hand even goes above
the level of the clavicle not necessarily reaching the site of stimulus. A
common misconception about the GCS is the equation of abnormal
flexion and extensor response to decorticate and decerebrate rigidity
respectively (these are based on the Sherrington experiments
corresponding to the level of lesion, mid-brain or brainstem) [7]. In
head injury the severity correlates with the GCS score irrespective of the site. A poor motor response can be as a result of severe cortical or
hemispheric lesions.
M3 & 4 (Normal/Abnormal flexion): What is important to
document among these responses is if the patient demonstrates
any degree of flexion. The patients who show any degree of flexion
response on a persistent basis do well overall than those who have
extensor posturing. One can also see a flexion response in the lower
limbs. Experienced personnel can make the distinction between
the two responses but inexperienced staffs particularly in the field
have difficulty in differentiating between these responses. It is not
of clinical importance to make a definite diagnosis between M3
and M4 as decisions like intubation, CT scan etc are unlikely to be
influenced only on this parameter. Patient who is not localizing to
painful stimulus is more likely to be in the severe than moderate
head injury group. A range of movement is possible in a patient
who is not localizing to painful stimulus. It can vary from a “Normal
Flexion” which is rapid withdrawal, abduction of shoulder with
external rotation. In “Abnormal Flexion” there is adduction, internal
rotation of shoulder (classical decorticate posture). Between these
two extremes of movements there may be varied patterns and
also both types of movements may be seen at the same time in a
patient. One simple and practical way to sort out between the two
responses is done by observing the position of the forearm. If the
forearm is in pronation then it is labelled as M3. The forearm is
in supination without localizing to the painful stimulus then it is
labelled as M4. In the situation of a difference in the motor score, it
is best to manage as per the lower score. When there is a difference
of 1, a moderate head injury may be diagnosed as severe (GCS- 8
or 9). It is only a mathematical probability and an unlikely clinical
situation that the patient has E4V5M4. Such gross differences in the
individual parameters can occur with focal brain injuries. This way
the management will not be hampered by this difference in eliciting
motor response. Depending on the patient’s response to the treatment
initiated one can decide the future course of action. One needs to take
into account that a patient’s response can be varied when tested by
two different people or at different times. It is not always a stereotyped
response that is uniformly seen in these patients.
M2 (Extension response): The classic “decerebrate” posturing.
Shoulder adducted, elbow extended, wrist hyerpronated, hip and
knee extended with ankle plantar flexed.
M1 (None): This is when there is no response to a painful stimulus.
One should be very careful when deciding this response especially
in spinal injuries with quadriparesis. The patient if conscious can
be asked to show his/her tongue to document a M6 response. One
should take into account of any muscle relaxants or sedative agents
before concluding that there is no motor response. What is important
during the assessment is that patients, who localize to painful stimulus
and those who do not, should be identified without ambiguity at the
earliest. It is possible that a patient is M5 but falls in the severe head
injury. The GCS of E1V1M5, E2V1M5 or E1V2M5 are not commonly
encountered in clinical scenario. More often than not, patients who
are M5 fall in the moderate head injury group. When GCS scale like
E1V1M6 is encountered, it is likely to be due to observer error rather
than a real clinical situation. In situations like hypotension, hypoxia,
intoxicants, sedation/relaxants and other confounding factors it is
important to document these at the time of GCS assessment. Later
when these are corrected one can correlate the GCS with that. The
low GCS may be entirely due to this factor eg: hypotension which
once corrected the GCS improves. It may also be that this is just one
of the elements involved. One should also document the neurological
status, pupils at the time of intubation so that a follow up can be
done to see the progress. GCS should be calculated of the full score
including all 3 parameters and not of two. For example GCS-9 out
of 10 in an intubated patient will convey an inaccurate picture than
E4VETM5.
How much change is significant?
On clinical monitoring a change in GCS of 1 is a sign that after
some time it is to be checked. Further decrease in the score merits
an investigation and intervention if indicated. A drop in the GCS
of 2 or more means that one needs to revaluate the patient, plan a
repeat investigation and medical or surgical intervention as and when
indicated.
How frequently should it be assessed?
The issue of how frequent should the assessment be done can be
resolved by using common sense on a case-by-case basis. There cannot
be fixed criteria for this. A simple measure is a patient who comes
sooner after the injury and is a poorer grade should be monitored
more closely than a patient who has reported after a significant time
after injury and is in a good grade. The frequency of monitoring also
depends on the number of personnel and number of patients being
monitored.
How to communicate GCS?
The acronym stands for both Glasgow Coma Scale (individual
components) and Score (total). The scale is used to decide the
management of individual patients. The score will help in measuring
outcome of group of patients with same score. It is always advisable
to mention the complete score with its individual parameters than
just the total score. If one parameter is not assessable due to any cause
(periorbital swelling precluding eye opening response assessment)
then this should be mentioned as such and the total should not be
made excluding this parameter. A GCS of 9/10 when Verbal response
cannot be assessed will not convey the right meaning and can cause
errors in management. When in serious doubt, the actual response
can be described verbatim so that the message is not lost in translation.
Confounding factors that make testing of GCS parameters
untenable [8,9]
Drugs- anaesthetics, sedatives, neuromuscular blockades, anti
psychotics
Cranial nerve injuries
Spinal cord injuries
Intoxicants (alcohol or drugs)
Hearing impairment
Limb injuries with or without splints
Dysphasia
Pre-existing illnesses eg: dementia, psychiatric conditions
Ocular injuries
Language and Cultural barriers
Table 1
Conclusion
The GCS is a very simple, fast, easy and objective method of assessment of neurological condition especially in head injury. One needs to be aware of the fact that the GCS assessment does have certain lacunae in terms of overall picture of the patient. There is no mention of vitals, pupils or any other parameters. One needs to look at the GCS in context to the overall clinical picture of the patient. Adding too many other parameters to circumvent this, will take away the simple objective nature of GCS assessment.
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