How to Assess the Glasgow Coma Scale (GCS) Score
Assess the GCS by evaluating three components separately—Eye opening (1-4), Verbal response (1-5), and Motor response (1-6)—with the motor component being the most critical predictor of neurological outcome, especially in sedated or intubated patients. 1
The Three Components
The GCS was created by Teasdale and Jennett in 1974 as a standardized tool for serial neurologic assessments 2. You must score each component independently and report all three values (Eye-Verbal-Motor), not just the total 1.
Eye Opening Response (1-4 points)
- 4 points: Opens eyes spontaneously
- 3 points: Opens eyes in response to voice
- 2 points: Opens eyes only to painful stimuli
- 1 point: Does not open eyes at all
Verbal Response (1-5 points)
- 5 points: Oriented and converses normally
- 4 points: Confused, disoriented
- 3 points: Utters inappropriate words
- 2 points: Incomprehensible sounds
- 1 point: Makes no sounds
Motor Response (1-6 points)
- 6 points: Obeys commands
- 5 points: Localizes painful stimuli
- 4 points: Flexion/withdrawal to painful stimuli
- 3 points: Abnormal flexion to painful stimuli (decorticate response)
- 2 points: Extension to painful stimuli (decerebrate response)
- 1 point: Makes no movements
Critical Clinical Considerations
The Motor Component is Most Important
The motor response remains the most robust predictor of outcome and correlates best with injury severity, particularly when patients are sedated or intubated 1. When eye and verbal responses cannot be assessed due to sedation or intubation, the motor component alone provides reliable prognostic information 1.
Always Include Pupillary Assessment
You must assess pupillary size and reactivity alongside the GCS score 1. These findings, combined with age and initial GCS, are validated predictors of 6-month neurological outcome in large studies (IMPACT: 6,681 patients; CRASH: 8,509 patients) 1.
Serial Assessments Are Essential
A single GCS score has limited prognostic value 2. Serial GCS measurements are crucial for detecting neurological deterioration—approximately 13% of patients who eventually became comatose had an initial GCS of 15 2.
Recommended frequency for serial assessments:
- Moderate TBI (GCS 9-13): Every 15 minutes for the first 2 hours, then hourly for 12 hours 1
- Mild TBI (GCS 13-15): Every 30 minutes for the first 2 hours, then hourly for 4 hours 1
A decrease of ≥2 points in GCS score warrants immediate repeat CT imaging 1.
Special Situations
Intubated or Sedated Patients
When verbal response cannot be assessed, use the pre-sedation GCS score rather than assuming normality 4. If unavailable, the motor and eye components alone provide reliable assessment 1. The motor score can be predicted from eye and motor components using validated regression models if needed 5.
Timing of Assessment
Assess GCS after correcting systemic factors that cause secondary brain insults, particularly hypotension (systolic BP <90 mmHg) and hypoxemia, as these significantly worsen outcomes 1.
Common Pitfalls to Avoid
- Don't rely on a single GCS measurement for diagnosis or prognosis in mild TBI 2
- Don't assume GCS 13-15 means "safe"—up to 15% of patients with GCS 15 have acute intracranial lesions on CT 2
- Don't forget to document each component separately (E-V-M format), not just the total score 1
- Don't overlook the motor component in intubated patients—it remains the most valuable predictor 1
Interpretation
- GCS 13-15: Mild TBI
- GCS 9-12: Moderate TBI
- GCS 3-8: Severe TBI
- GCS 3: Deep coma or death
The GCS was designed for serial evaluations to facilitate communication between providers and detect deterioration, not as a standalone diagnostic tool 2. It does not replace a complete neurological examination 2.