A 45-year-old man is brought in after a fall. He opens his eyes when you shout his name, pulls his hand away and mutters incomprehensible sounds when you apply pressure to his nail bed, and does not speak in words.
What is his GCS — and what does that number actually tell the next doctor who sees this patient?
Why GCS Exists
The Glasgow Coma Scale was designed in 1974 for one purpose: to give clinicians a reproducible, common language for describing conscious level, so that "he seems a bit drowsy" from a night nurse and "GCS 13" from the day team mean the same thing to everyone who reads them. It is a communication tool as much as a scoring tool — its real value is in trending over time, not in the single number at one moment.
The Three Components
GCS is not one score — it's three, added together. Always document it as E + V + M, never just the total. "GCS 10" could mean very different things depending on which component is low, and the breakdown is what actually guides your assessment.
| Eye Opening (E, max 4) | Verbal Response (V, max 5) | Motor Response (M, max 6) |
|---|---|---|
| 4 — Spontaneous | 5 — Orientated | 6 — Obeys commands |
| 3 — To voice | 4 — Confused conversation | 5 — Localises to pain |
| 2 — To pain | 3 — Inappropriate words | 4 — Withdraws from pain |
| 1 — None | 2 — Incomprehensible sounds | 3 — Abnormal flexion (decorticate) |
| 1 — None | 2 — Extension (decerebrate) | |
| 1 — None |
The motor score (M) is the single strongest predictor of outcome in traumatic brain injury of the three components — it correlates most closely with severity of brain injury and prognosis. If you can only reliably assess one component in a difficult patient (e.g. eyes swollen shut, intubated), the motor response carries the most clinical weight.
Scoring It Correctly — Common Mistakes
Where Scores Go Wrong at the Bedside
- Applying pain incorrectly: Central stimulation (trapezius squeeze, supraorbital pressure) is required to assess the best motor response — peripheral stimulation (nail bed pressure) can trigger a spinal reflex withdrawal that looks like localisation but isn't. Use central stimulus for the true motor score.
- Recording "best" vs "worst" limb: Always score the best motor response of any limb — if the right arm localises but the left is flaccid (e.g. from a stroke or peripheral injury), the right arm's response is what you document, with a note explaining the asymmetry.
- Intubated patients: Verbal score cannot be assessed — document as "VT" (verbal-tube) rather than assigning a default 1, and score total as e.g. "E3 VT M5." Some systems use 1T to keep the total score calculable.
- Confusing "confused" with "inappropriate": Confused conversation (V4) means the patient is talking in coherent sentences but disorientated. Inappropriate words (V3) means random or exclamatory words with no conversational exchange. These are commonly conflated.
- Not re-checking after correcting a reversible cause: Hypoglycaemia, opioid overdose, and post-ictal states can all mimic a low GCS from brain injury. Correct reversible causes, then reassess — don't anchor on the first number.
Severity Bands
| Total GCS | Severity | Typical Implication |
|---|---|---|
| 13–15 | Mild | Observe, consider CT per NICE/local head injury rules |
| 9–12 | Moderate | CT head, close observation, consider HDU-level care |
| ≤8 | Severe | Airway at risk — the classic teaching is "GCS 8, intubate" to protect the airway |
"GCS 8, intubate" is a memory aid, not an absolute rule. The actual decision to secure the airway is based on the patient's ability to protect their own airway (gag/cough reflex, risk of aspiration) and their trajectory — a GCS of 9 that is rapidly falling may need earlier intubation than a stable GCS of 8. Examiners like to test whether you understand this nuance rather than just quoting the number.
Trend, Don't Just Snapshot
A single GCS score tells you where a patient is right now. Serial GCS — recorded at appropriate intervals and compared over time — tells you whether they're improving, static, or deteriorating, which is far more clinically useful. A drop of 2 or more points in the motor score, or any drop associated with a new unequal pupil, should prompt urgent reassessment and escalation — these are classic signs of an expanding intracranial mass lesion until proven otherwise.
Eyes open to voice (E3), incomprehensible sounds (V2), withdraws from peripheral pain — but on central stimulation (trapezius squeeze), he actually localises purposefully to the stimulus (M5). Correct score: E3 V2 M5 = GCS 10. This is a moderate head injury; the initially-assumed withdrawal response would have under-scored his motor function had central stimulation not been used to re-check it — a good example of why technique changes the number.
Always document E+V+M separately, not just the total. Use central pain stimulation for accurate motor scoring. Motor score predicts outcome best of the three. Record the best limb response, and note asymmetry. Trend the score over time — a falling motor score or new pupil asymmetry is a red flag regardless of the absolute number.
References
- Teasdale G, Jennett B. Assessment of Coma and Impaired Consciousness: A Practical Scale. The Lancet. 1974;304(7872):81–84.
- Teasdale G et al. The Glasgow Coma Scale at 40 Years: Standing the Test of Time. Lancet Neurology. 2014;13(8):844–854.
- NICE Guideline NG232: Head Injury — Assessment and Early Management. National Institute for Health and Care Excellence, 2023.
