Glasgow Coma Scale (GCS)
Standardized assessment of consciousness level after brain injury
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Why use it
Universal language for describing level of consciousness. Required component of trauma assessment (ATLS). Guides intubation decisions (GCS ≤ 8). Prognostic indicator after traumatic brain injury.
About
The Glasgow Coma Scale (GCS) is the most widely used scoring system for quantifying the level of consciousness in acute medical and trauma patients. It evaluates three components: eye opening, verbal response, and motor response. The total score ranges from 3 (deep coma) to 15 (fully alert). GCS is integral to trauma assessment, ICU monitoring, and prognostication after head injury.
When to use
- Initial assessment of trauma or head injury patients
- ICU monitoring of neurological status
- Decision-making for intubation (GCS ≤ 8 = protect airway)
- Serial assessment to detect neurological deterioration
- Triage and severity classification of traumatic brain injury
Formula
Pearls & pitfalls
- Always report individual components (e.g., E3V4M5 = 12) rather than just the total.
- GCS ≤ 8 is the classic threshold for intubation ("GCS 8, intubate").
- Motor component alone is the strongest predictor of outcome.
- GCS cannot be reliably assessed in intubated/sedated patients — document "T" for verbal if intubated.
- Asymmetric motor response: always score the BEST response observed.
- Alcohol and drugs confound GCS — reassess after metabolic clearance.
Next steps
GCS 13-15: Mild TBI. GCS 9-12: Moderate TBI, consider CT and close monitoring. GCS 3-8: Severe TBI, intubate and secure airway, urgent CT, neurosurgical consultation.
Evidence
Original publication in Lancet 1974. Updated GCS-Pupils (GCS-P) in 2018 adds pupil reactivity. Validated in thousands of studies as predictor of TBI outcome. IMPACT and CRASH models incorporate GCS for TBI prognostication.