About the Glasgow Coma Scale
The Glasgow Coma Scale (GCS) was developed by Graham Teasdale and Bryan Jennett at the University of Glasgow in 1974 to provide a standardised, reproducible assessment of level of consciousness in patients with acute brain injury. It has since become the most widely used neurological assessment tool in emergency medicine, intensive care, neurosurgery, and pre-hospital care globally. Current UK practice follows the NICE NG232 guideline on head injury assessment and early management.
GCS Component Summary
| Component | Score | Response |
|---|---|---|
| Eye (E) | 4 | Spontaneous |
| 3 | To voice | |
| 2 | To pain | |
| 1 | None | |
| Verbal (V) | 5 | Oriented |
| 4 | Confused | |
| 3 | Inappropriate words | |
| 2 | Incomprehensible sounds | |
| 1 | None | |
| Motor (M) | 6 | Obeys commands |
| 5 | Localises pain | |
| 4 | Withdrawal | |
| 3 | Abnormal flexion (decorticate) | |
| 2 | Extension (decerebrate) | |
| 1 | None |
Clinical Decision Thresholds
- GCS 15: Fully conscious and oriented, normal.
- GCS 13–15: Mild TBI, consider CT if LOC, amnesia, vomiting, or age >65. Anticoagulated patients presenting after a fall often warrant a concurrent cardiac work-up if there's any associated chest pain, see HEART Score.
- GCS 9–12: Moderate TBI, CT head mandatory, neurosurgical review, admit.
- GCS ≤8: Severe TBI, airway at risk, consider intubation, urgent CT, ICU. Ongoing ICU management follows the Brain Trauma Foundation's severe TBI guidelines, including ICP monitoring thresholds.
- GCS 3: Deepest coma, worst possible score; E1V1M1.
Important Limitations
- Verbal score cannot be assessed in intubated patients, document as GCS E_V(T)M_ where T denotes intubated.
- Eye opening may be affected by periorbital oedema, document as untestable (NT).
- GCS is not validated for children under 5, use the Paediatric GCS (pGCS) or AVPU scale.
- Pre-hospital GCS may be affected by hypotension, hypoxia, and sedation, post-resuscitation GCS is more prognostically reliable.
- GCS alone should not be used as the sole criterion for intubation, clinical judgement of airway protective reflexes is essential.
- Sedative and analgesic drugs used in critically ill patients with reduced GCS often require dose adjustment for renal function, see Creatinine Clearance.
Frequently Asked Questions
What does GCS 3T mean?
GCS 3T means the patient scored 3 on GCS but the T indicates they are intubated (T = tube), making verbal assessment impossible. It is written as GCS 3T or E1V(T)M1 to distinguish it from a non-intubated GCS of 3, as it prevents misinterpretation. Some centres use GCS scores such as E1VTM1 with the motor and eye components documented separately since verbal cannot be scored.
Is GCS 8 always an indication for intubation?
GCS ≤8 is a widely cited threshold for considering intubation to protect the airway, but it is a guideline, not an absolute rule. The critical assessment is the presence of protective airway reflexes (cough, gag), trajectory of consciousness (improving vs. deteriorating), cause of reduced GCS (metabolic causes may be rapidly reversible), and the clinical environment. A GCS of 8 in a steadily improving post-ictal patient differs significantly from GCS 8 in a deteriorating head injury. Always assess clinically.
What is the difference between decorticate and decerebrate posturing?
Decorticate posturing (M3, abnormal flexion) involves flexion of the arms at the elbows and wrists with extension of the legs, indicating damage above the red nucleus in the midbrain. Decerebrate posturing (M2, extension) involves extension and internal rotation of both arms and legs, indicating damage at or below the midbrain. Decerebrate posturing generally implies more severe and deeper brainstem injury and carries a worse prognosis than decorticate posturing.
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References
- Teasdale G, Jennett B. "Assessment of coma and impaired consciousness. A practical scale." Lancet. 1974;2(7872):81-84.
- Teasdale G, et al. "The Glasgow Coma Scale at 40 years: standing the test of time." Lancet Neurol. 2014;13(8):844-854.
- NICE Guideline NG232. Head Injury: Assessment and Early Management. NICE, 2023. Replaces NICE Clinical Guideline CG176 (2014).
- BTF Guidelines. Guidelines for the Management of Severe Traumatic Brain Injury. 4th ed. Brain Trauma Foundation, 2016.
⚠️ Medical Disclaimer: The GCS calculator is for clinical reference only. All neurological assessments and management decisions must be made by qualified healthcare professionals based on the full clinical picture. This tool does not replace clinical judgement.