The GCS is a neurological scale that provides a reliable, objective way of recording the conscious state of a patient. It was originally developed at the University of Glasgow in 1974 for assessment of head injury but is now used broadly in acute and critical care.

GCS 13–15: Mild brain injury — patient is likely alert and oriented. GCS 9–12: Moderate brain injury — patient may be confused or drowsy. GCS 3–8: Severe brain injury / coma — intubation is typically indicated for airway protection.

Reporting the total score alone can be misleading because the same total can represent very different clinical states. For example, E4V1M6 (total 11) is very different from E2V4M5 (total 11). The individual component scores provide more precise clinical information.

GCS may be unreliable in intubated patients (verbal component cannot be assessed), patients with facial trauma or swelling (eye component), sedated patients, or patients with spinal cord injury. In these cases, the component scores should be noted individually with explanations.