How do I perform a Glasgow Coma Scale (GCS) assessment?

How to Perform a Glasgow Coma Scale (GCS) Assessment

The GCS must be assessed by evaluating three separate components—Eye opening (E), Verbal response (V), and Motor response (M)—and documenting each component individually rather than as a single summed score. 1

Core Assessment Components

The GCS evaluates consciousness through three distinct domains that should always be reported separately (e.g., E3 V4 M5): 1, 2

Eye Opening Response (E1-E4)

• E4: Opens eyes spontaneously
• E3: Opens eyes in response to voice
• E2: Opens eyes only to painful stimuli
• E1: Does not open eyes to any stimulus 3

Verbal Response (V1-V5)

• V5: Oriented and converses normally
• V4: Confused, disoriented speech
• V3: Utters inappropriate words
• V2: Incomprehensible sounds
• V1: Makes no sounds 3

Motor Response (M1-M6)

• M6: Obeys commands
• M5: Localizes painful stimuli (purposeful movement toward pain)
• M4: Flexion/withdrawal to painful stimuli (pulls away from pain)
• M3: Abnormal flexion to painful stimuli (decorticate posturing)
• M2: Extension to painful stimuli (decerebrate posturing)
• M1: Makes no movements 3

Critical Documentation Principles

Always document each component separately using the format "E___ V___ M___" rather than providing only a total score. 1, 4 The motor component is the most reliable predictor of neurological outcome and should be prioritized, especially when other components cannot be assessed. 1, 4

When Components Cannot Be Assessed

Use non-numeric designations for untestable elements rather than assigning arbitrary scores: 4

• For intubated patients: Document as "VT" or "V-intubated"
• For periorbital swelling preventing eye opening: Document as "E-untestable"
• Never assign V=1 or E=1 when these components cannot be assessed 4
• Do not calculate a sum score when any component is untestable 4

Assessment Technique

Applying Painful Stimuli

When assessing motor response, apply a standardized painful stimulus: 5, 6

• Apply central pain (trapezius squeeze or supraorbital pressure) to assess best motor response
• Peripheral pain (nail bed pressure) may be used but can produce withdrawal reflexes that don't reflect true cortical function
• Observe the patient's best response—use the highest score achieved

Serial Assessments

Serial GCS measurements are far more valuable than a single determination for detecting neurological deterioration. 2 A declining GCS score (decrease of ≥2 points) indicates secondary neurological worsening and warrants immediate imaging. 1

For moderate traumatic brain injury (GCS 9-13), repeat assessments should occur: 1

• Every 15 minutes for the first 2 hours, then hourly for 12 hours (Scandinavian approach)
• Every 30 minutes for 2 hours, then hourly for 4 hours (UK approach)
• Every hour (Australian approach)

Special Populations and Situations

Intubated or Sedated Patients

Assess the GCS before sedation and intubation whenever possible; if unavailable, document the pre-intubation score from emergency services. 4 When patients are sedated or paralyzed, postpone clinical examination until at least five elimination half-lives of the longest-acting drug have elapsed. 4

In intubated patients, rely primarily on the motor response (M1-M6) combined with pupillary assessment, as these remain the most robust indicators of brain injury severity. 1, 4

Patients with Periorbital Swelling

When eye opening cannot be assessed due to periorbital swelling, focus on the motor response and supplement with pupillary size and reactivity, which provide strong independent prognostic information. 4 Consider automated pupillometry where available for greater sensitivity. 4

Alternative: FOUR Score

The Full Outline of Unresponsiveness (FOUR) score can be used in heavily sedated or intubated patients as it evaluates eye response, motor response, brainstem reflexes, and respiratory pattern without requiring verbal assessment. 4 However, limited clinical experience and potential confounding from ventilator modes should be acknowledged. 4

Correcting Confounding Factors Before Final Assessment

Address physiologic confounders that can artificially lower GCS scores: 4

• Maintain mean arterial pressure ≥80 mmHg in severe traumatic brain injury
• Prevent and correct hypoxemia
• Reverse residual sedation cautiously (flumazenil carries seizure risk)
• Correct hypothermia, sepsis, and metabolic/respiratory derangements

Supplementary Assessment

Always assess and document pupillary size and reactivity separately from GCS components, as these are independent predictors of outcome in traumatic brain injury. 1, 4

Common Pitfalls to Avoid

• Do not use the GCS sum score alone to diagnose mild traumatic brain injury—approximately 13% of patients who become comatose initially present with GCS 15. 2
• Do not assign arbitrary numeric values to untestable components—this creates false precision and misleading documentation. 4
• Do not assess GCS during active sedation or paralysis—wait for drug clearance or document confounding factors. 4
• The motor component requires the most skill to assess accurately—inadequate training is a major source of inter-rater variability. 5, 7