What is the Glasgow Coma Scale, how is it scored, and what do the scores indicate for patient management?

Glasgow Coma Scale: Clinical Assessment and Management

What is the Glasgow Coma Scale?

The Glasgow Coma Scale is a 15-point clinical tool developed in 1974 that assesses consciousness through three objective components—Eye Response (1-4 points), Motor Response (1-6 points), and Verbal Response (1-5 points)—with total scores ranging from 3 (deep coma) to 15 (normal consciousness). 1

The scale was specifically designed to provide reliable, reproducible neurological evaluations that enable clear communication between healthcare providers about patient status, particularly in head injury and coma assessment. 2, 1

How to Score the GCS

Three Components:

• Eye Response (E): 1-4 points 1

  • 4 = Spontaneous eye opening
  • 3 = Opens eyes to verbal command
  • 2 = Opens eyes to pain
  • 1 = No eye opening

• Motor Response (M): 1-6 points 1

  • 6 = Obeys commands
  • 5 = Localizes to pain
  • 4 = Withdraws from pain
  • 3 = Abnormal flexion (decorticate)
  • 2 = Abnormal extension (decerebrate)
  • 1 = No motor response
  • Note: The motor component is the most prognostically valuable and most difficult to assess accurately 3, 4

• Verbal Response (V): 1-5 points 1

  • 5 = Oriented
  • 4 = Confused conversation
  • 3 = Inappropriate words
  • 2 = Incomprehensible sounds
  • 1 = No verbal response

Clinical Interpretation and Management Thresholds

Severity Classification:

• GCS 13-15: Mild TBI 5
• GCS 9-12: Moderate TBI 5
• GCS ≤8: Severe TBI (typically requires intubation and intensive care) 1
• GCS 3-5: Very severe TBI (extremely high mortality, approaching 100% in certain subgroups) 6

Critical Management Thresholds:

Any patient with GCS <14 meets critical physiologic criteria requiring immediate transport to a trauma center, with documented mortality rates of 24.7%. 1, 5 This is a mandatory trigger for trauma center transport according to CDC guidelines. 1

• GCS ≤8: Requires immediate intubation, intensive care admission, and neurosurgical consultation 1
• GCS 9-12: Requires urgent neuroimaging (CT scan), neurosurgical consultation, and close monitoring with substantial risk (>20%) of secondary neurological deterioration 5
• GCS 12: Specifically indicates moderate TBI with significant neurological compromise requiring urgent evaluation 5
• GCS 5: Represents very severe injury requiring immediate trauma center transport and consideration for neurosurgical intervention, though prognosis remains grave 6

Monitoring Requirements

Serial GCS assessments provide substantially more valuable clinical information than single determinations—a declining score or persistently low score indicates poorer prognosis. 1, 5

Recommended Monitoring Frequency:

• Severe TBI (GCS ≤8): Every 15 minutes for first 2 hours, then hourly for following 12 hours (Scandinavian protocol) 5, 6
• Moderate TBI (GCS 9-12): Every 30 minutes for first 2 hours, then hourly for following 4 hours (UK protocol), or hourly assessments (Australian protocol) 5

Documentation Requirements:

Always document individual component scores (E, M, V) at each assessment rather than just the sum score, as patients with identical totals but different component profiles may have different outcomes. 1, 5, 4 The motor component has the highest predictive value in severe TBI. 1, 4

Red Flags Requiring Immediate Action:

A decrease in GCS by ≥2 points from baseline represents a critical red flag requiring immediate repeat CT scanning and escalation of care. 5, 6

Prognostic Value

The GCS correlates with mortality and functional outcomes, especially when assessed serially. 1 However, the individual components often provide more prognostic information than the sum score alone. 1, 4

• Motor component: Highest prognostic value in severe TBI 4
• Combined three components: Consistently higher prognostic value than sum score alone across different TBI severities 4
• Component profiles: Significant variations in mortality exist between different component profiles despite identical sum scores 4

Critical Limitations and Pitfalls

The GCS was originally designed for comatose patients and serial evaluations, not for single-point severity determination or mild TBI assessment. 5, 6

Major Confounding Factors:

• Sedation and paralytic medications 6, 7
• Intubation (prevents verbal response assessment) 6, 7
• Facial trauma (affects eye and verbal components) 6
• Intoxication (alcohol, drugs) 6
• Metabolic disturbances 6

Key Clinical Caveats:

• A single GCS determination is insufficient to diagnose mild TBI or determine the full extent of parenchymal injury 1, 5
• Clinical decision-making, particularly regarding treatment limitations, should never rely solely on the GCS score 6
• The scale was not intended to supplant a comprehensive neurological examination 5
• Training is essential: In one study, 50% of ICU nurses (37% with ≥5 years experience) incorrectly scored the motor component on pretesting, though 93% were correct after training 3

Best Practices for Implementation

• Perform serial assessments to monitor trends rather than relying on single measurements 1, 5
• Document individual component scores (E, M, V) at each assessment 1, 5
• Use the GCS alongside other assessments: Pupillary size and reactivity must be documented at each assessment as key prognostic indicators 6
• Maintain systolic BP >100 mmHg or MAP >80 mmHg to prevent secondary brain injury 5
• Recognize limitations and consider alternative assessment tools when confounding factors are present 1, 6
• Ensure proper training on all three components, with particular focus on the motor component which is most difficult to assess 3

Global Impact

The GCS is officially employed in more than 75 countries and is incorporated into the WHO Classification of Diseases 11th Revision. 1 Over 37,633 scientific articles spanning 1974-2022 have referenced the GCS, with a compound annual growth rate of 16.7% in publications. 1 It is most commonly employed in internal medicine (23%), critical care (22%), and neurotrauma (20%) clinical practice guidelines. 1