Glasgow Coma Scale
Teasdale and Jennett published the Glasgow Coma Scale (GCS) in the Lancet in 1974 as an aid in the clinical asssment of post-traumatic unconsciousness. It was devid as a formal scheme to overcome the ambiguities that aro when information about comato patients was prented and groups of patients compared. The GCS has three components: eye (E), verbal (V) and motor (M) respon to external stimuli. The best or highest respons are recorded. The scale consisted of 14 points, but was later adapted to 15, with the division of the motor category ‘flexion to pain’ into two further categories (Figure 1).
Figure 1: Glasgow Coma Scale (GCS, Teasdale and Jennett 1974) (illustration taken from Laureys et al. 2002)
So far, more than 4500 publications have appeared to its u (MEDLINE arch performed in October 2005) (Figure 2). It is a component of the Acute Physiology and Chronic Health Evaluation (APACHE) II score, the (Revid) Trauma Score, the Trauma
and Injury Severity Score (TRISS) and the Circulation, Respiration, Abdomen, Motor, Speech (CRAMS) Scale, demonstrating the widespread adoption of the scale.
Figure 2: Number of scientific papers making reference to the Glasgow Coma Scale (from Laureys et al. 2005).
The prence of spontaneous eye opening “indicates that the arousal mechanisms of the brainstem
are active” (Teasdale and Jennett 1974). Prerved arousal does not imply the prence of awareness. Patients in a vegetative state have awakened from their coma but remain completely unaware of their environment and lf. Most comato patients who survive will eventually open their eyes, regardless of the verity of their cerebral injuries (Jennett 1972). Indeed, less than 4% of head-injured patients never open their eyes before they die (Bricolo et al. 1980). The eye opening in respon to speech tests the reaction “to any verbal approach, whether spoken or shouted, not necessarily the command to open the eyes” (Teasdale and Jennett 1974). Again, this respon is obrved in vegetative patients who can be awakened by non-specific auditory stimulation. In the patients it is recommended to differentiate between a reproducible respon to command and to non-n speech. Eye opening in respon to pain should be tested by a stimulus in the limbs, becau the grimacing associated with supraorbital or jaw-angle pressure may cau eye closure.
After arousing the patient the prence of verbal respons indicates the restoration of a high degree of interaction with the environment (i.e. awareness). An oriented conversation implies awareness of the lf (e.g., the patient can answer the question: “What is your name?”) and environment (e.g., the patient correctly answers the questions: “Where are we?” and “What year/month is it?”). Confud speech is recorded when the patient is capable of producing language,
for instance phras and ntences, but is unable to answer the questions about orientation. When the patient prents intelligible articulation but exclaims only isolated words in a random way (often swear words, obtained by physical stimulation rather than by a verbal approach) this is scored as “inappropriate speech”. Incomprehensible sounds refer to moaning and groaning without any recognizable words. This rudimentary vocalization does not necessitate awareness and is thought to depend upon subcortical functioning as it can be obrved in anencephalic children and vegetative patients.
The motor respon first asss whether the patient obeys to simple commands, given in verbal, gestural or written form. A non-specific sound stimulus may induce a reflex contraction of the patient’s fingers or alternatively such a reflex respon can result from the physical prence of the examiner’s fingers against the palm of the patient (i.e., grasping reflex). Before accepting that the patient is truly obeying commands, it is advid to test that the patient will also relea and squeeze again to repeated commands. If there is no respon a painful stimulus is applied. First, pressure is applied to the fingernail bed with a pencil. If flexion is obrved stimulation is then applied to other sites (applying pressure to the supraorbital ridge, pinching the trapezium or rubbing the sternum) to differentiate between localization (i.e., a stimulus at more than one site caus a limb to move so as
to attempt to remove it by crossing the midline), withdrawal flexion (i.e., a rapid flexion of the elbow associated with abduction of the shoulder) or ‘abnormal’ flexion (i.e., a slower stereotyped flexion of the elbow with adduction of the shoulder that can be achieved when stimulated at other sites). Stereotyped flexion respons are the most common of the motor reactions obrved in verely brain-injured patients; they are also the most enduring (Born 1988). Extensor posturing is more easily distinguished and is usually associated with adduction, internal rotation of the shoulder and pronation of the forearm. The term ‘decerebrate rigidity’ should be avoided becau it implies a specific physioanatomical correlation. Abnormal flexion and extension motor respons often co-exist (Bricolo et al. 1977). It is important to appreciate that it is the best respon that should be scored and that abduction movements reflect some residual awareness while stereotyped postures do not. The prence of asymmetrical respons are significant in indicating that there is a focal as well as a diffu disturbance of brain function, and this should be noted parately. The side showing the impaired respon locates the site of the focal brain damage and the level of the best respon of the better side reflects the extent of general depression in brain function. The scale of respons to pain is applicable to the movements of the arms. The movements of the legs are not only more limited in range, but may take place on the basis of a spinal withdrawal reflex (e.g., in brain death, a spinal reflex may still cau the legs to flex briskly in respon to pain applied locally (Ivan 1973)).
It is very tempting to sum the three components of the GCS (E-V-M) into a total score, ranging from 3 to 15. However, given the incread u of intubation, ventilation and dation of patients with impaired consciousness before arrival at specialists units, and even before arrival at hospital (Marion and Carlier 1994), patients might wrongly being scored as GCS 3/15 rather than being more appropriately reported as impossible to asss or score. In a recent study of 1005 patients with head injuries in European centers, asssment of each of the three components of the GCS was possible only in 61% of patients before hospital, in 77% on arrival at the first hospital, in 56% on arrival in the neurosurgical unit, and in 49% of ‘post-resuscitation (Murray et al. 1993). The inappropriate scoring of abnt responsiveness as 3 has led to some data indicating that the mortality of patients with a score of 3 is apparently lower than that of tho with a score of 4. Summing GCS components has also been criticized on a purely mathematical basis. Becau there are only four units assigned to the eye respons, versus five to the verbal and six to the motor respons, the scale incorporates a numerical skew toward motor respon. This problem can be tackled by weighting individual scores for eye, verbal and motor respons in such a way that each has a minimum contribution of one and a maximum of five (Bhatty and Kapoor 1993). This approach, however, is too complicated for practical u. Moreover, this effort to provide mathematical parity for the three components has abutted against studies that have stresd the particular importance of the motor portion of the GCS.
Indeed, the motor score is more important than either of the other two components in predicting the magnitude of neurologic injury for patients with vere head injury (Jagger et al. 1983). While verbal and eye scores are more pertinent in patients who are not, in fact, comato. It is a widespread but erroneous usage to define mild brain injury as a summed score ranging from 13-15, moderate injury, 9-12, and vere injury, 3-8. Indeed, in the persistent vegetative state, patients open their eyes spontaneously (E4) and may make moaning sounds (V2) or flex abnormally to pain (M3), while their condition hardly reflects “moderate” brain injury. For
clinical purpos, summation of the GCS is too impreci (Bozza Marrubini 1984). To achieve a total score of 6 to 12 there are more than 10 simple combinations of variables, each with very different clinical profiles. In Glasgow, patients are always described by the three parate respons and never by the total (Teasdale et al. 1983). It is, therefore, good practice to communicate the GCS in terms such as “patient scored E2, VT, M4” and only sum its three components for rearch applications.
Pitfalls
Untrained or inexperienced obrvers produce unreliable scoring of consciousness (Rowley and Fiel
ding 1991). In one study, one out of five ICU workers were mistaken when asked to make judgments as to whether patients were ‘conscious’ or ‘unconscious’, (Teasdale and Jennett 1976). Consciousness needs considerable skill to evaluate and the obrver should be aware of the pitfalls encountered at ICU ttings. It is also well known that the preceding score of the patient frequently influences the examinator when rating the patient’s prent state of consciousness. It therefore is recommended to score in a “blinded” manner.
Obviously, problems ari when the eyes are swollen shut, either following periorbital edema, direct ocular trauma, facial injury, craniotomy, cranial nerve VII injury or neuromuscular blockade. In the circumstances the enforced closure of the patient’s eyes should be recorded on his chart by marking “C” (= eyes clod) (Teasdale 1975). In deep coma, flaccid eye muscles will show no respon to stimulation yet the eyes remain open if the lids are drawn back. Such opening should be recorded as unresponsive. It is important to stress that although opening of the eyes implies arousal, it does not necessarily mean that the patient is aware.
Continued speechlessness may be due to caus other than unawareness (e.g., neuromuscular blockade, intubation via the oropharynx or through a tracheostomy, fractured mandible or maxillae, edematous tongue, deafness, foreign language, dysphasia, confusion or delirium). The evaluation of
verbal respons is also biad when patients are dated, alcohol or drug intoxicated or too young to speak. The u of early intubation and administration of neuromuscular paralyzing agents in the pre-hospital pha of care has rendered verbal and motor respons unmeasurable in the cas. Early treatment was uncommon when the GCS was first described, but has since gained greater acceptance. The FOUR (Wijdicks et al. 2005) and RLS85 (Starmark et al. 1988) which do not include a verbal respon criterion, are the most notable alternative for scoring intubated patients. Several other techniques have been propod to designate the verbal score in intubated patients. Some have propod to assign an arbitrary score of one point to all intubated patients (Marshall et al. 1983). Others have created a pudo-score by averaging the testable scores and adding this calculated score to the sum in lieu of the verbal score (Grahm et al. 1990). Linear regression predication of the verbal scores bad on the other two scores has also been utilized (Meredith et al. 1998). The best alternative is to report parate respons, using a non-numerical designation of “T” (= intubated) when the verbal score cannot be assd and not to sum the respons (Marion and Carlier 1994). The patient’s verbal respon may also be impaired as a result of a single focal lesion of the speech areas in the dominant hemisphere, that is, aphasia. The asssment of such a patient’s language ability requires a specialized evaluation (e.g., written instructions and written replies in the ca of motor dysphasia). The level of verbal respon should still be indicated but an
appropriate note may be made that the impairment is considered to be due to dysphasia (“D”= dysphasia) (Teasdale 1975). Motor respons cannot be reliably monitored in cas of spinal cord, plexus or peripheral nerve injury or in the prence of splint or immobilization devices. As previously stated, one must take care not to interpret a grasp reflex or postural adjustment as a respon to command.
In most scoring systems, awareness is assd as the level of obeying to commands. This approach cannot be applied to cas where the patient is clinically or pharmacologically paralyzed yet alert (e.g., locked-in syndrome, vere polyneuropathy or u of neuromuscular blocking agents) or tho with psychogenic unresponsiveness. It is important to stress that special effort should be made to identify and exclude the
rare caus of pudo-coma. The GCS has also been critiqued for lacking reliability in monitoring levels of consciousness in patients with moderate brain injury (Segatore and Way 1992). More detailed scales are recommended for the asssment of awareness in the patients (Malkmus et al. 1980; Majerus and Van der Linden 2000). Finally, as consciousness is a subjective first person experience, we remain with the theoretical limitation to the certainty of our clinical asssment of consciousness (since it is in another person that the clinician has to infer the prence or abnce of
conscious experience) (Bernat 1992).
Even if the GCS is the most widely ud and validated tool to evaluate the state of consciousness, it also is the most frequently misud. One study showed that 51% of patients were incorrectly assd (Crossman et al. 1998). It is important to stress that for clinical u, patients should be communicated by the three parate scores (E, V, M and R) and never by the total sum. If eye or verbal respons cannot be evaluated, this should be indicated by marking a “C” (eyes clod) or “T” (intubated), respectively. References (text adapted from Laureys et al. 2002)
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