How is the Glasgow Coma Scale (GCS) score calculated?

Glasgow Coma Scale (GCS) Calculation

The Glasgow Coma Scale (GCS) is calculated by adding scores from three components: Eye Opening (1-4 points), Verbal Response (1-5 points), and Motor Response (1-6 points), resulting in a total score ranging from 3-15, with lower scores indicating more severe neurological impairment.

Components of the GCS

1. Eye Opening (E) - 1 to 4 points

• 4: Spontaneous - eyes open without stimulation
• 3: To verbal stimuli - eyes open to speech
• 2: To pain - eyes open only to painful stimuli
• 1: No response - eyes do not open to any stimulation

2. Verbal Response (V) - 1 to 5 points

• 5: Oriented - aware of person, place, time, and situation
• 4: Confused - engaged in conversation but disoriented
• 3: Inappropriate words - random or exclamatory articulated speech
• 2: Incomprehensible sounds - moaning, groaning
• 1: No response - no verbalization even to painful stimuli

3. Motor Response (M) - 1 to 6 points

• 6: Obeys commands - follows simple instructions
• 5: Localizes pain - purposeful movement toward painful stimulus
• 4: Withdraws from pain - pulls away from painful stimulus
• 3: Abnormal flexion - decorticate posturing
• 2: Abnormal extension - decerebrate posturing
• 1: No response - no movement to any stimulation

Clinical Interpretation

The total GCS score is used to classify traumatic brain injury (TBI) severity 1:

• Mild TBI: GCS 13-15
• Moderate TBI: GCS 9-12
• Severe TBI: GCS ≤8

Special Considerations

Intubated Patients

When patients are intubated, the verbal component cannot be assessed directly. Options include:

1. Record the score as "ET" (endotracheal tube) or "T" alongside the eye and motor scores (e.g., E3M5VT)
2. Use a regression model to estimate the verbal score based on eye and motor scores 2, 3:
   • Estimated Verbal Score = -0.3756 + (Motor Score × 0.5713) + (Eye Score × 0.4233)

Pediatric Patients

Modified versions exist for pediatric patients who cannot provide verbal responses due to developmental stage 4, 1. The pediatric GCS (pGCS) adjusts verbal responses based on age-appropriate communication.

Serial Assessments

Serial GCS assessments are crucial for detecting neurological deterioration. A decrease of 2 or more points should prompt immediate reevaluation 1.

Common Pitfalls

1. Failing to assess all components separately before calculating the total score
2. Misinterpreting disorientation due to intoxication or medication effects
3. Not performing serial assessments to detect changes over time
4. Improper pain stimulus application when assessing motor response
5. Confounding factors such as sedation, neuromuscular blockade, or intoxication may artificially lower scores 1

Clinical Significance

The GCS is incorporated into numerous clinical guidelines and decision-making tools, including trauma triage protocols. Patients with GCS <14 require transport to a trauma center, with those scoring GCS ≤8 needing immediate transfer to the highest level of trauma care available 1.

The motor component of the GCS has been shown to contain most of the predictive power of the total score in some studies 5, but the complete scale provides the most comprehensive assessment.