Glasgow Coma Scale - an overview (2023)

Glasgow Coma Scale

The Glasgow Coma Scale (seeTable 2.5) is a scoring scale of eye opening and motor and verbal responses that can be administered to individuals to objectively measure the level of consciousness and severity of the head injury. The responses are scored between 1 and 5 with a combined total score of 3 to 15, with 15 being normal. An initial score of less than 5 is associated with an 80% chance of being in a lasting vegetative state or death. An initial score of greater than 11 is associated with 90% chance of recovery. Concussions are usually rated between 13 and 15. Its primary use in evaluating individuals for concussion is to rule out more severe brain injury and to help determine which individuals need immediate emergent medical attention.¹³³

The first test relates to eye opening. Eye opening may occur spontaneously, in response to speech or pain, or there may be no response at all. Each of these responses is given a numeric value: spontaneous eye opening—4; response to speech—3; response to pain—2; and no response—1. Spontaneous opening of the eyes indicates functioning of the ascending reticular activating system. This finding does not necessarily mean that the patient is aware of the surroundings or of what is happening, but it does imply that the patient is in a state of arousal. A patient who opens his or her eyes in response to the examiner’s voice is probably responding to the stimulus of sound, not necessarily to the command to open the eyes. If unsure, the examiner may use different sound-making objects (e.g., bell, horn) to elicit an appropriate response.

The second test involves motor response; the patient is given a grade of 6 if there is a response to a verbal command. Otherwise, the patient is graded on a 5-point scale depending on the motor response to a painful stimulus (seeTable 2.5). When scoring motor responses, it is the ease with which the motor responses are elicited that constitutes the criterion for the best response. Commands given to the patient should be simple, such as, “Move your arm.” The patient should not be asked to squeeze the examiner’s hand, nor should the examiner place something in the patient’s hand and then ask the patient to grasp it. This action may cause agrasp reflex, not a response to a command.¹⁸⁵

If the patient does not give a motor response to a verbal command, then the examiner should attempt to elicit a motor response to a painful stimulus. It is the type and quality of the patient’s reaction to the painful stimulus that constitute the scoring criteria. The stimulus should not be applied to the face, because painful stimulus in the facial area may cause the eyes to close tightly as a protective reaction. The painful stimulus may consist of applying a knuckle to the sternum, squeezing the trapezius muscle, or squeezing the soft tissue between the thumb and index finger (Fig. 2.47). If the patient moves a limb when the painful stimulus is applied to more than one point or tries to remove the examiner’s hand that is applying the painful stimulus, the patient is localizing and a value of 5 is given. If the patient withdraws from the painful stimulus rapidly, a normalwithdrawal reflex is being shown and a value of 4 is given.

The Glasgow Coma Scale

Low GCS has been shown to correlate with poor outcomes, with mortality rates as high as 76% for patients with a post-resuscitative GCS of 3 (Baxt and Moody, 1987; Marshall et al., 1991). As the GCS was developed as a serial exam, a single field GCS is of limited utility (Winkler et al., 1984). A decreasing GCS is more predictive of poorer outcome than an initially low GCS (Marshall et al., 1991; Servadei et al., 1998), while a GCS trending up is predictive of improved outcomes (Winkler et al., 1984). In children as well, an improving GCS increases rates of survival (White et al., 2001). Patients with an initially high GCS that remains high have the best outcomes and some authors have suggested that in isolated head trauma, patients with a serial GCS of 14 or 15 may not need transport to a designated trauma center (Horowitz and Earle, 2001; Ellis et al., 2007).

However, the GCS has several limitations. Most importantly, it requires an interactive patient. The GCS is best determined by the prehospital provider only after correction of other sources of blunted neurologic response, including opiate overdose, hypoglycemia, hypoxemia, or hypoperfusion. Further, it must be performed prior to sedation or paralysis. If the patient has evidence of airway compromise, a cursory GCS evaluation should be performed in tandem with preparation for airway maneuvers requiring sedatives or paralytics. It also must be stressed that the GCS is intended for serial examinations and outcomes cannot be adequately determined until a trend in GCS has been established.

Glasgow Coma Scale

The GCS is a 15-point scale used in an attempt to quantify the patient's LOC and is an objective method of following the patient's neurologic status (Table 34.2). It was originally developed during a time when CT scanning was not available to communicate changes in neurologic status in comatose patients with TBI (Fig. 34.6). The score assigns points based on the patients best eye opening (spontaneous opening = 4 to no response = 1), motor response (obeys commands = 6 to no response = 1), and verbal response (oriented = 5 to no response = 1). Due to its ease of use, it has been adopted in the routine assessment of all trauma patients, including those with MTBI who are not comatose.⁵ However, the GCS score can reflect impairment from conditions other than brain injury, such as distracting injuries, intoxication from drugs and alcohol, hypoxemia, and sedative medications. Furthermore, patients can deteriorate from an expanding intracranial hematoma after what appears clinically to be a mild brain injury. Although TBI is often categorized into mild, moderate, and severe based on the GCS score, it really represents a spectrum of injury.

Glasgow Coma Scale

Glasgow Coma Scale.

Although it has not been systematically validated as a prognostic scoring system for infants and young children as it has in adults, GCS is frequently used in the assessment of pediatric patients with an altered level of consciousness. The GCS is the most widely used method of evaluating a child's neurologic function and has 3 components. Individual scores for eye opening, verbal response, and motor response are added together, with a maximum of 15 points (Table 81.3). Patients with a GCS score ≤8 require aggressive management, generally including stabilization of the airway and breathing with endotracheal intubation and mechanical ventilation, respectively, and if indicated, placement of an intracranial pressure monitoring device. TheFull Outline of Unresponsiveness (FOUR) score is another useful assessment and monitoring tool (seeTable 85.1).

Glasgow Coma Scale

However, the GCS has been the standard scoring assessment throughout the world for 20 years. It seems unlikely that it will be easily replaced, even by potentially superior scoring systems. The Innsbruck and the Edinburgh-2 Coma Scales have some of the same problems as the GCS but the Reaction Level Scale (RLS 85) has a number of advantages over the others.

The level of alertness

Behavioral Evaluation

In 1974, Teasdale and Jennett's Glasgow coma scale (GCS) was published in ‘The Lancet.’ This standardized bedside tool to quantify consciousness became a medical classic, thanks mainly to its short and simple administration. The GCS measures eye, verbal, and motor responsiveness. There may be some concern as to what extent eye-opening is sufficient evidence for assessing brainstem function. Additionally, the verbal responses are impossible to be measured in cases of intubation and tracheotomy. Most importantly, the GCS is not sensitive enough to detect transition from the VS toward the MCS.

To differentiate VS patients from MCS patients, the most appropriate scale is the coma recovery scale-revised (CRS-R). The CRS-R has a similar structure to the GCS, containing, in addition to motor, eye, and verbal subscales, also auditory, arousal, and communication subscales. Despite its longer administration (i.e., c. 20min) as compared to the GCS and the full outline of unresponsiveness (FOUR), it is the most sensitive in differentiating VS patients from MCS patients. This is because it assesses every behavior according to the diagnostic criteria of the VS and the MCS, such as, the presence of visual pursuit and visual fixation. Importantly, the way we assess these behavioral signs need to be standardized and uniform, permitting between-centers comparisons. For example, for the assessment of visual pursuit, some scales use an object or finger (FOUR), some use a mirror, a person, an object, and a picture (Western Neuro-Sensory Stimulation Profile), some use an object and a person (Wessex Head Injury Matrix; Sensory Modalities Assessment and Rehabilitation Technique), and some a moving person (Coma/Near Coma Scale). We have shown that the use of a mirror is more sensitive in detecting eye tracking and, hence, identify MCS patients. These findings stress that self-referential stimuli have attention-grabbing properties and are important in the assessment of DOC.

Despite their pros and cons, each scale contributes differently in establishing the diagnosis and prognosis of DOC. The administration and interpretation of findings should be decided and discussed in terms of the person who uses the scale, the place where it is administered (e.g., intensive care vs. chronic rehabilitation settings), and the reasons for administration (e.g., clinical routine vs. research purposes).

Injury severity

Using traditional severity measures such as the Glasgow Coma Scale (GCS) (Teasdale and Jennett, 1974), post-traumatic amnesia, and duration of unconsciousness, a dose-response relationship has been clearly demonstrated between injury severity and post-TBI impairment, with increasing TBI severity associated with reduced cognitive abilities and behavior and social problems. Logically, this relationship makes sense, with a TBI of increased severity resulting in more damage to the brain and a longer recovery time, impacting skill acquisition. Some functional domains seem to be particularly vulnerable to TBI though, with difficulties in attention, language, and behavior reported even after mild TBI (Yeates et al., 1997; Anderson et al., 2001, 2006; Dennis and Barnes, 2001; McKinlay et al., 2002; Crowe et al., 2013).

In young children, defining TBI severity accurately can be difficult, as the GCS relies on verbal responses and these skills are not developed in early childhood; therefore the GCS is modified to account for this. Further, the immature language skills in young children make post-traumatic amnesia, another commonly used measure of TBI severity, difficult to ascertain.

Brain pathology identified on neuroimaging may also provide insights into recovery. Recently studies have moved from conventional imaging to looking at quantifying structural changes and examining brain volumes. For example, recent research using novel structural imaging techniques from our group showed that the number of lesions on susceptibility-weighted imaging was a significant predictor of IQ outcomes (Beauchamp et al., 2013). Similarly, white matter loss in the corpus callosum was correlated with full scale IQ and parental ratings of social integration (Gale and Prigatano, 2010). Research utilizing diffusion imaging studies has reported associations between brain pathology and neurobehavioral outcomes (Wozniak et al., 2007; Ewing-Cobbs et al., 2008; Levin et al., 2008; Babikian et al., 2009). For example, reduced white matter integrity in the frontal region and corpus callosum has been associated with reduced processing speed and cognitive and motor outcomes after TBI in children (Ewing-Cobbs et al., 2008; Levin et al., 2008). Reduced white matter integrity in the frontal and supracallosal regions of the brain has also been correlated with executive function outcomes (Wozniak et al., 2007).

Severity measures

The most common severity assessment for TBI is the Glasgow Coma Scale score (GCS) (Teasdale and Jennett, 1974; Shah and Kelly, 2003). This score is commonly used in prehospital settings and in EDs and is the total of three combined scores: Glasgow Motor, Glasgow Verbal, and Glasgow Eye movement. Each component of the score identifies the patient's crude functional status. It has also been shown to be a useful system in determining TBI severity (Evans, 2006). Early severity classification of TBI is based partly on the use of the GCS, where 80% of all head injuries are mild TBI (GCS score between 13 and 15) (Kraus and Norjah, 1988), 10% are classified as moderate TBI (GCS score between 9 and 12), and the remaining 10% are classified as severe, scoring 8 or less on GCS (Saatman et al., 2008). Although GCS is more frequently calculated in the ED, GCS data collected at the injury scene also helps guide the transport of the patient to the appropriate healthcare facility (Sasser et al., 2012). However, differences in injury scene GCS and ED GCS can lead to inaccurate predictions of TBI severity 15% of the time (Andriessen et al., 2011). Substance use and intubation, as well as facial swelling, can interfere with an accurate GCS assessment.

Other severity measures of TBI have been studied but were deemed unreliable when applied to TBI. Examples of TBI severity measures include LOC and post-trauma amnesia (PTA), which are commonly collected on state surveillance datasets (Marr and Coronado, 2004) and trauma registries. The LOC has been shown to be an unreliable predictor of a TBI diagnosis, with studies showing the presence of LOC and a TBI diagnosis occurs at different frequencies, such as 32%, (Walker et al., 2007), 36% (Boswell et al., 2002), and 50% (Dutton et al., 2011). Another severity measure is PTA which is measured using units of time of the amnesia after the injury. Such information is collected from the patient immediately after the trauma event. Immediate PTA has also been an unreliable predictor of a diagnosis of TBI because not every patient has PTA. However, when present, the duration of PTA is a good indicator of the extent of cognitive and functional deficits after TBI (Khan et al., 2003) and it is considered to be a good predictor of outcome (Alexander, 1995; Bowen et al., 1999; Nakase-Richardson et al., 2011). Nonetheless, the validity of self-reported data and the ability of a TBI patient to recognize their cognitive, behavioral, and emotional symptoms have been called into question for people sustaining a TBI (Sbordone et al., 2000) as up to 25% of patients change their self-evaluation of symptoms over a 3 month time period (Gronwall and Wrightson, 1980). Thus, as a measure, PTA, which involves cognition, has limited usefulness during the diagnosis of TBI.

Because most TBIs are classified as mild, some researchers have attempted to develop further categorizations of mild TBI. An early example to further categories of mild TBI was made by Esselman and Uomoto (1995), who developed a classification of mild TBI injury into grades I–IV. Their classification of mild TBI into graded categories based on severity made use of many symptoms (amnesia, loss of consciousness, confusion, anatomic lesions, abbreviated injury scoring, and the duration of symptoms). Approximately 41 different classification scales of gradations of mild TBI severity have been developed (Anderson et al., 2006). Overall, these progressive efforts have not been integrated into medical practice because there is no consensus among experts on the best grading system for mild TBI (Cobb and Battin, 2004).