What is the Glasgow Coma Scale (GCS)?
The Glasgow Coma Scale (GCS) is the standard tool for assessing a patient's level of consciousness. Introduced in 1974 by Graham Teasdale and Bryan Jennett, it measures a patient's responsiveness through three independent parameters: eye opening, verbal response, and motor response. It is used daily in the emergency department, prehospital emergency care, intensive care, and head trauma to reproducibly quantify neurological status and monitor its evolution.
How the GCS score is calculated
The total score is obtained by summing the three parameters and ranges from a minimum of 3 (no response in any category) to a maximum of 15 (fully alert and oriented patient). The breakdown is also recorded, e.g. GCS 10 (E3 V3 M4), because two patients with the same total can have different clinical pictures.
| Points | Response | Description |
|---|---|---|
| 4 | Spontaneous | Eyes open spontaneously |
| 3 | To verbal command | Eyes open to verbal stimulus |
| 2 | To pain | Eyes open only to painful stimulus |
| 1 | None | No eye opening |
| Points | Response | Description |
|---|---|---|
| 5 | Oriented | Response oriented to time and place |
| 4 | Confused | Confused, disoriented response |
| 3 | Inappropriate words | Words disconnected from context |
| 2 | Incomprehensible sounds | Moaning, meaningless sounds |
| 1 | None | No verbal response |
| Points | Response | Description |
|---|---|---|
| 6 | Obeys commands | Correctly performs motor commands |
| 5 | Localizes pain | Brings hand to painful stimulus |
| 4 | Withdraws from pain | Withdraws the limb from painful stimulus |
| 3 | Abnormal flexion | Decorticate — pathological flexion |
| 2 | Abnormal extension | Decerebrate — pathological extension |
| 1 | None | No motor response |
Interpreting the GCS score
The normal value is 15. The severity of impaired consciousness is usually classified into three bands:
- GCS 13–15Mild impairment — clinical monitoring.
- GCS 9–12Moderate impairment — urgent assessment.
- GCS ≤ 8Severe impairment (coma) — possible indication for intubation.
The GCS ≤ 8 threshold is clinically important because it identifies coma and a patient with a potentially compromised airway: it's the practical rule "GCS 8, intubate", always to be weighed against the overall clinical picture. A GCS of 3 is the lowest possible score and indicates complete absence of response.
Pediatric GCS: child and infant
In young children and infants the verbal response is adapted for age, since they cannot respond like an adult: vocalizations, babbling, and consolable or inconsolable crying are assessed instead. Eye opening and motor response remain similar to the adult version. The calculator above includes the Adult, Child, and Infant profiles with their respective descriptions.
Read more on the pediatric Glasgow Coma Scale (modified GCS) with complete tables for children and infants by age group.
FOUR score: the alternative to GCS for the intubated patient
The FOUR score (Full Outline of UnResponsiveness), developed by Wijdicks et al. (2005) at the Mayo Clinic, was created to overcome the main limitation of the GCS: the verbal response cannot be assessed in the intubated, sedated, or aphasic patient, who ends up systematically receiving the minimum score on that component (often noted "GCS-T"). The FOUR score replaces the verbal response with brainstem reflexes and adds a respiratory component, remaining usable even in the ventilated patient.
It evaluates four components — eye (E), motor (M), brainstem (B), and respiration (R) — each scored 0–4, for a total of 0 to 16 (16 = normal consciousness). Unlike the GCS, the FOUR score does not have an equally well-established three-tier threshold convention in the literature; in practice the ≤8 threshold is still used by analogy with the GCS for airway assessment, while a score of 0 — absence of brainstem reflexes, motor response, and spontaneous breathing — indicates a formal brain death evaluation pathway per local protocol, without constituting a diagnosis by itself.
Validation studies have shown inter-rater reliability comparable to or better than the GCS, with the added advantage of detecting incipient brain herniation (through pupillary reflexes) that the GCS alone does not capture.
Sources: Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974;2(7872):81-84. Wijdicks EF, Bamlet WR, Maramattom BV, Manno EM, McClelland RL. Validation of a new coma scale: The FOUR score. Ann Neurol. 2005;58(4):585-593. This tool is for educational and support purposes: it does not replace clinical judgment or local protocols.