Glasgow Coma Scale (GCS)

Anatomy or system affected: Neurological and brain systems

Definition: The Glasgow Coma Scale is a neurological tool for assessing the level of consciousness of a patient suffering from a brain injury.

Key terms:

abnormal flexion response: an involuntary extension of the arms or legs that indicates severe brain injury

brain trauma: any kind of injury sustained to the brain due to trauma (hitting one's head on the ground after a fall) or nontraumatic event such as brain swelling due to a virus

minimally conscious state: a condition of severely altered consciousness in which minimal, but definite, behavioral evidence of self or environmental awareness is demonstrated

persistent vegetative state: a severely altered state of consciousness that occurs several weeks after a coma, which results in very limited self-awareness or response to outside stimulation

Description and Background Information

The Glasgow Coma Scale (GCS) was created out of a need for a standardized assessment of consciousness to track the severity of brain trauma after head injury. Prior to its creation in 1974 by Graham Teasdale and Bryan Jennett, both from the University of Glasgow's Institute of Neurological Sciences, individual doctors assessed consciousness subjectively. The GCS provided the first objective method of assessment for tracking symptoms over the course of days, weeks, and months during the recovery process. The GCS has three sections: eye opening, verbal response, and motor response. Eye opening is used to assess visual response to speech, pain, and the surrounding environment. Eyes that open spontaneously receive the highest score (4), while no eye opening receives the lowest score (1). Verbal response assesses the degree to which a patient can intelligently respond to a question such as: What year is it? If the response indicates that the person is aware of his environment, time and situation, then he will receive a score of 5. If the person does not respond at all, then a score of 1 will be assessed. Motor responses assess the ability of the patient to respond physically to commands, shown in arm movement and shoulder abduction. Correctly obeying a simple command to the request “Show me two fingers” will result in the highest score (6) and a flaccid response will produce the lowest score (1).

Patients are given a GCS score of 3 to 15. (Note: Older versions of GCS use a 14 score system, in which abnormal flexion under motor response is omitted.) A score of 13–15 indicates mild trauma, a score of 9–12 moderate trauma, and a score of 3–8 severe trauma. In medical records, a GCS recording will usually appear using the following symbols: GCS 11 = E3 V6 M2, often followed by the hour and minute in which the evaluation was administered. The equation provides the total score of the patient and secondary scores broken into the three subsections. GCS is the total score.

Deficiencies of the Glasgow Coma Scale

The Glasgow Coma Scale measures symptoms that can supplement additional medical data that will aid a physician in coming to a diagnosis. It is a behavioral assessment to give us a glimpse into the biological explanation for what is occurring in the brain. Because the scale results are reliant upon the observations of medical personnel, as with other behaviorally oriented assessments, a margin for error does exist. Therefore, the scale is useful in giving rough estimations of severity of symptoms, but it is inadequate in identifying the cause of unresponsiveness. Employing additional medical testing, such as an magnetic resonance imaging (MRI) or computed tomography (CT) scan, can significantly contribute to a more definitive diagnosis for what might have caused problems related to awareness and consciousness.

The scale has proven to be reliable but not valid in many cases. It is simple and short to read and apply. Therefore, most medical personnel can use it to record symptom progress with consistency and ease. However, the symptoms that are being tracked may have no connection to the cause of the injury. For example, if dealing with a patient with eye impairment, their eye opening scores will be inadequate, not because of a diminishment of consciousness levels but because of deficiencies in the ability to control eye movement. If a patient has a lesion on his brain stem, the patient's scores could misrepresent the level of brain trauma since the lesion is in an area that could compromise his ability to display awareness.

To compensate for GCS deficiencies, additional scales have been developed, the most prominent being the Pediatric Glasgow Coma Scale (PGCS). PGCS has the same 3–15 score rating scale as the GCS but changes the criteria for specific scores so that it is appropriate for a child younger than 36 months who has undeveloped motor and verbal response skills. Instead of speech, inconsolable crying or moaning is assessed; and instead of motor response, bodily posture is assessed.

Science and Profession

Because of its universality, multiple specialists within the medical profession use the GCS. Neurologists, emergency room doctors, and nurses utilize the scale to measure levels of consciousness within a hospital setting. Emergency medical technicians use it upon arrival at the scene of a consciousness-related trauma. GCS training is taught in medical schools and emergency medical services (EMS) courses.

Perspective and Prospects

For decades, the GCS has been regarded as the “gold standard” for a simple-to-use behavioral assessment tool to assess the level of consciousness. However, in 2004, Giacino and colleagues introduced the Coma Recovery Scale-Revised (CRS-R), which includes several additional subscales to the GCS. In addition, there are more standardized procedures to follow in order to improve upon the variability that can come from different assessors. The CRS-R has been helpful to differentiate patients considered to be in a persistent vegetative state from those who are in a minimally conscious state. Additional assessment methods are being investigated that use the electroencephalogram (EEG) as a means to determine the degree to which conscious brain activity is present in someone who cannot verbalize their thoughts.

Bibliography

Bruno, Marie-Aurelie, and Steven Laureys. “Uncovering Awareness: Medical and Ethical Challenges in Diagnosing and Treating the Minimally Conscious State.” Cerebrum (June, 2010): 12.

Giacino, Joseph, and Kathleen Kalmar. “Coma Recovery Scale-Revised 2006.” The Center for Outcome Measurement in Brain Injury. http://www.tbims.org/combi/crs/crsref.html

Okamura, Kumiko. “Glasgow Coma Scale Flow Chart: A Beginner’s Guide.” British Jour. of Nursing 23.20 (2014): 1068–1073. CINAHL Plus with Full Text. Web. 16 Mar. 2015.

McLernon, Siobhan. “The Glasgow Coma Scale 40 Years On: A Review of Its Practical Use.” British Jour. of Neuroscience Nursing 10.4 (2014): 179–184. CINAHL Plus with Full Text. Web. 16 Mar. 2015.

Teasdale, Graham, and Bryan Jennett. “Assessment of Coma and Impaired Consciousness: A Practical Scale.” The Lancet 13, no. 7872 (1974): 81–84.