How do you properly assess the Glasgow Coma Scale (GCS)?

How to Properly Assess the Glasgow Coma Scale (GCS)

The GCS should be assessed by evaluating three distinct components—eye opening (E), verbal response (V), and motor response (M)—with each component scored independently and documented separately, not just as a sum score, because patients with identical totals but different component profiles may have vastly different outcomes and prognoses. 1

Core Assessment Components

Eye Opening Response (E1-4)

• E4: Eyes open spontaneously
• E3: Eyes open to verbal command
• E2: Eyes open to painful stimulus only
• E1: No eye opening 1

Verbal Response (V1-5)

• V5: Oriented and conversing
• V4: Confused conversation
• V3: Inappropriate words
• V2: Incomprehensible sounds
• V1: No verbal response 1

Motor Response (M1-6)

The motor component has the highest predictive value and remains the most robust indicator even in sedated patients. 1 This is also the most difficult component to assess correctly and requires specific training. 2

• M6: Obeys commands
• M5: Localizes to painful stimulus
• M4: Withdraws from pain
• M3: Abnormal flexion (decorticate posturing)
• M2: Abnormal extension (decerebrate posturing)
• M1: No motor response 1, 2

Critical Assessment Principles

Document Component Scores Separately

Always record individual E, V, and M scores (e.g., E3V4M5 = 12) rather than just the sum. 1 Patients with identical total scores but different component profiles have different outcomes—for example, E4V3M5 and E3V4M5 both equal 12 but represent different neurological states. 1

Apply Painful Stimulus Correctly

When assessing motor response, apply a painful stimulus centrally (supraorbital pressure or trapezius squeeze) to distinguish between localization (M5) and withdrawal (M4). 2 Peripheral stimuli alone may not accurately differentiate these responses. 2

Assess Pupils Simultaneously

The GCS should be routinely combined with assessment of pupillary size and reactivity, which are key prognostic indicators. 1 Document pupillary findings at each GCS assessment. 1

Perform Serial Assessments

Serial GCS assessments provide substantially more valuable clinical information than single determinations, with declining scores indicating poorer prognosis. 1 A decrease of at least two points in the GCS score should prompt immediate repeat CT scanning. 1

Timing of Assessments Based on Severity

For Moderate TBI (GCS 9-12)

• Every 15 minutes for the first 2 hours 1
• Then hourly for the following 12 hours 1
• Continue hourly assessments thereafter until stable 1

For Mild TBI (GCS 13-15)

• More frequent early monitoring if GCS <14, as mortality rates reach 24.7% at this threshold 1
• GCS <14 alone warrants the highest level of trauma activation 3

Common Pitfalls and Confounding Factors

Recognize Assessment Limitations

Critical confounding factors that may affect GCS assessment include: 1

• Sedation and analgesics: Wait appropriate time after stopping medications for reliable assessment 4
• Intubation: Verbal component cannot be assessed; document as "VT" (intubated) 5
• Facial trauma: May prevent eye opening assessment 1
• Intoxication: May artificially lower scores 1

Avoid the "Mild Head Injury" Assumption

A GCS of 14 does NOT represent "mild" head injury—it is automatically classified as high-risk and has a 23% risk of positive CT findings requiring intervention. 6 Patients with GCS <14 treated at Level I trauma centers had reduced mortality compared to Level II centers (OR: 0.7; 95% CI: 0.6-0.9). 3

Training Requirements

50% of ICU nurses with ≥5 years experience incorrectly assessed the motor component in pre-training testing, but 93% were correct after focused education. 2 This underscores that proper GCS assessment requires specific training, particularly for the motor component. 2

Prognostic Value

Motor Score for Post-Cardiac Arrest

A GCS motor score >3 on day 4 after cardiac arrest predicts favorable outcome at 6 months with 84% specificity and 77% sensitivity. 4 Assessment within the first 4 days can identify patients with increased likelihood of favorable outcome. 4

Severity Classification

• Severe TBI: GCS 3-8 3
• Moderate TBI: GCS 9-12 1
• Mild TBI: GCS 13-15 3

However, any GCS <14 represents significant injury requiring intensive monitoring and neurosurgical consultation availability. 3, 6