Glasgow Coma Scale (GCS): Understanding & Interpretation

The Glasgow Coma Scale (GCS) Overview

The Glasgow Coma Scale (GCS) is a neurological scale used to assess the level of consciousness in patients, particularly those with head injuries or brain damage.

What is consciousness?

In the medical context, consciousness has three requirements. To be conscious, you have to be:

• Awake: This includes whether or not you have the ability to wake up because of voice or touch. That’s what makes a coma different from just being asleep.
• Alert: This is how responsive you are to people talking to you and if you’re able to understand what’s happening in your immediate surroundings.
• Oriented: This means you know who you are, where you’re at, what day it is and other details related to the here and now.

Components of GCS

The GCS consists of three components:

1. Eye Opening (E): Scores range from 1 (no response) to 4 (spontaneous opening).
2. Verbal Response (V): Scores range from 1 (no response) to 5 (oriented and conversational).
3. Motor Response (M): Scores range from 1 (no response) to 6 (obeys commands).

Scoring & Interpretation

The total GCS score ranges from 3 (comatose) to 15 (fully awake and responsive).

Interpretation

• Severe brain injury: GCS 3-8
• Moderate brain injury: GCS 9-12
• Mild brain injury: GCS 13-15

Method of Use

The GCS Assessment Aid has four steps to the assessment process: Check, observe, stimulate, rate.

GCS Score Chart

GCS Cheat Sheet

Limitations

1. Not applicable to children under 5 years old.
2. May not accurately assess patients with:
   • Intubation or sedation.
   • Hearing or language barriers.
   • Pre-existing cognitive impairment.

Clinical Applications

1. Initial assessment of head injury severity.
2. Monitoring neurological status.
3. Guiding treatment decisions.
4. Predicting patient outcomes.

Glasgow Coma Scale (GCS) Scoring and Interpretation:

Eye Opening (E)

1. No response (1 point)
2. To pain (2 points)
3. To voice (3 points)
4. Spontaneous (4 points)

Verbal Response (V)

1. No response (1 point)
2. Incomprehensible sounds (2 points)
3. Inappropriate words (3 points)
4. Confused, disoriented (4 points)
5. Oriented, conversational (5 points)

Motor Response (M)

1. No response (1 point)
2. Extension (2 points)
3. Flexion (3 points)
4. Withdrawal (4 points)
5. Localized movement (5 points)
6. Obeys commands (6 points)

Total Score

3-8: Severe brain injury (coma)
9-12: Moderate brain injury
13-15: Mild brain injury

GCS Categories

• Coma: GCS 3-8
• Vegetative state: GCS 9-12
• Locked-in syndrome: GCS 13-15 (with impaired motor response)

GCS-based Prognosis

• Good recovery: GCS 13-15
• Moderate disability: GCS 9-12
• Severe disability: GCS 5-8
• Death: GCS 3-4

TBI Assessment Using GCS

• Mild TBI: GCS 13-15. These patients are awake, can present with confusion but are able to follow directions and communicate.
• Moderate TBI: GCS 9-12. These patients are typically drowsy or obtunded, they can open eyes and localise painful stimuli upon assessment.
• Severe TBI: GCS 3-8. These patients present as obtunded to comatose, they are unable to follow directions. They may exhibit decorate or decerebrate posturing.

GCS-P

In 2018, a team of experts — including one of the original creators of the GCS — published an updated version of the GCS called the “GCS-P.” The P stands for “pupil,” as in the pupil of the eye. This is a fourth number that providers subtract from the standard GCS score.

Pupil reaction is important because it’s an indicator of your brain function. When your pupils don’t react to light, it’s a sign that a serious problem or injury is affecting your brain. The pupil score ranges from 0 to 2.

The pupil scores mean:

• 2: Neither pupil reacts to light.
• 1: One pupil doesn’t react to light.
• 0: Both pupils react to light.

Subtracting the pupil reaction score from the GCS score means that the GCS-P score can range from 1 to 15. The GCS-P score still uses a score of 8 or fewer to mean a coma.

A GCS score of 3 and a pupil score of 2 is a GCS-P score of 1. That means a very deep coma and no pupil reaction in both eyes.

Important Considerations

1. Intubation or sedation may affect scoring.
2. Language barriers or pre-existing cognitive impairment may impact verbal response.
3. GCS is not applicable to children under 5 years old.

Clinical Decision-Making

1. Initial GCS score guides treatment decisions.
2. Serial GCS assessments monitor neurological status.
3. Changes in GCS score indicate improvement or deterioration.

REFERENCES

1. Jain S, Iverson LM. Glasgow Coma Scale. [Updated 2023 Jun 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513298/
2. Teasdale G, Jennett B: Assessment of coma and impaired consciousness: A practical scale. Lancet 304:81–84, 1974
3. Teasdale G, Galbraith S, Clarke K: Acute impairment of brain function-2. Observation record chart. Nurs Times 71:972–3e, 1975
4. Teasdale G, Jennett B: Assessment and prognosis of coma after head injury. Acta Neurochir (Wien) :1976
5. Teasdale G, Knill-Jones R, Van Der Sande J: Observer variability in assessing impaired consciousness and coma. J Neurol Neurosurg Psychiatry:1978
6. Teasdale G, Murray G, Parker L, Jennett B: Adding up the Glasgow Coma Score. Acta Neurochir Suppl (Wien) 28:13–6, 1979
7. Middleton PM: Practical use of the Glasgow Coma Scale; a comprehensive narrative review of GCS methodology. Australas Emerg Nurs J:2012
8. Ernstmeyer K, Christman E, editors. Nursing Fundamentals [Internet]. 2nd edition. Eau Claire (WI): Chippewa Valley Technical College; 2024. PART IV, NURSING PROCESS. Available from: https://www.ncbi.nlm.nih.gov/books/NBK610818/

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