Glasgow Coma Scale (GCS)
What Is It?
The Glasgow Coma Scale, named for Glasgow Scotland where it was first described, is a simple way that physicians communicate the severity and depth of coma in a patient who has suffered traumatic brain injury. Mental alertness varies from fully alert to lethargic and stuporous all the way to deep coma, where a patient is minimally responsive or unresponsive to external stimuli. The GCS grades this level of consciousness on a scale from 3 (worst, deep coma) to 15 (normal, alert).
What Is the Purpose of the Glasgow Coma Scale?
The Glasgow Coma Scale (GCS) allows physicians to quickly and easily communicate the severity of a patient's head injury in the first hours or days after the trauma. It is therefore often used to follow the condition of the patient in the first several days in the hospital. Additionally, the GCS is a good prognostic indicator. This means that the early GCS is good at predicting the long term recovery of a patient. For example, patients who present in a deep coma, with a very low GCS generally do the worst while patients who present with a normal or close to normal mental alertness (higher GCS) very often make a very good recovery. The level of recovery is often graded as well, with the Glasgow Outcome Scale
How Is the Glasgow Coma Scale Score Determined?
The GCS is the cumulative score of three areas of examination. Eye, Verbal and Motor function are all tested by the clinician and the findings dictate the GCS. For the Eye exam, the patient is graded from 1 to 4. For the Verbal, the patient can receive from 1 to 5. For the Motor exam, the patient can receive from 1 to 6. Therefore, the lowest score possible is 3, receiving a 1 for each of the three categories. The best response is used to determine the score for each so if the patient only opens one eye, for example, they would receive a 4, not a 1 because one eye is closed. This avoids artificially lowering the score due to other factors, such as eye trauma in this case.
The grading of each component is described below:
Best Eye Response
- No eye opening to any stimulation.
- Eye opening only in response to pain.
- Eye opening to speech.
- Eyes are open spontaneously.
Best Verbal Response
- No verbal response.
- Incomprehensible sounds (such as moaning, but not saying words).
- Inappropriate words (such as random, profanity or exclamatory speech; forms words but not normal in response to conversation).
- Confused (the patient speaks and answers questions but is confused or disoriented).
- Oriented (the patient is coherent and appropriate and knows their name, age, date, etc.).
Best Motor Response
- No motor response (no movement, even to painful stimuli).
- Extension to pain (this is also called decerebrate posturing, it is a specific type of primitive reflex that is seem when higher brain function is significantly impaired but the brain stem is still functioning somewhat).
- Abnormal flexion to pain (also called, decorticate posturing, another type of primitive reflex which is abnormal).
- Withdrawal to pain (the patient obviously pulls away the part of the body being stimulated).
- Localizes to pain (this means that the patient makes purposeful movements toward a painful stimuli, attempting to push away the stimulus).
- Obeys commands (the patient follows simple commands such as "show me two fingers" or "wiggle your toes").
The GCS score is the sum of the three scores received for the Eye, Verbal and Motor responses. In the case of an intubated patient (one with a tube in their trachea to help them breath), Verbal function cannot be tested. These patients are given the worst score, a 1, but a modifier is usually attached to indicate this. For example, a T (for Tube) or V (for ventilated) is added, such as GCS 8T.
In general, head injury is classified as mild, moderate or severe based on the Glasgow Coma Scale as such:
- Mild: GCS ≥ 13
- Moderate: GCS 9 - 12
- Severe: GCS ≤ 8
Why are the coma responses "to pain" or "painful stimuli"?
Patients in deeper levels of coma do not respond at all to subtle stimuli such as gentle touch or speech. To assess the level of their neurological functioning, it is necessary to stimulate them more strongly. There are several ways that a clinician does this including pinching, pressure on the nail bed of their finger or toes, pressure on the rim of their orbit above their eyes, or a chest rub with their knuckles. It can look like the doctor or nurse is hurting the patient, but because this is only done in deeply comatose patients, they do not consciously perceive it.
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