The FOUR Score: Purpose and Application in Evaluating Patients
The FOUR (Full Outline of UnResponsiveness) score provides a more complete assessment of brainstem function than the Glasgow Coma Scale (GCS) and is particularly valuable for evaluating unresponsive patients, especially those who are intubated or have limited verbal responses. 1
Components and Advantages of the FOUR Score
The FOUR score consists of four components, each scored from 0-4:
- Eye response: Assesses ocular responses to command and pain, providing more detailed information than the GCS eye component 1
- Motor response: Evaluates limb responses to command and pain, similar to GCS but with additional nuance 1
- Brainstem reflexes: Measures pupillary responses and other brainstem functions, which are not assessed in the GCS 1
- Respiration pattern: Evaluates breathing patterns, which is particularly useful for intubated patients 1
Key Advantages Over GCS
- Assessment of intubated patients: Unlike GCS, the FOUR score does not rely on verbal responses, making it more useful for evaluating intubated patients 1
- Brainstem function evaluation: Incorporates assessment of pupillary responses and other brainstem reflexes, which are strong predictors of outcome 1
- Respiratory pattern assessment: Evaluates breathing patterns, though volume assist ventilator modes may confound differentiation between the two lowest scores 1
- Better discrimination in severely unresponsive patients: Can distinguish between patients who would all score the minimum on the GCS 2
- Recognition of locked-in syndrome: Can identify patients with preserved consciousness despite inability to respond verbally or motorically 2
Clinical Applications
Diagnostic Applications
- Neurocritical care monitoring: Provides reproducible measures of neurological state to chart trends in clinical progress 1
- Assessment of disorders of consciousness: Helps differentiate between various states of impaired consciousness 1
- Evaluation of brainstem function: Particularly useful in assessing patients with brainstem injuries or pathologies 1
Prognostic Value
- Mortality prediction: Shows good to excellent prognostication of in-hospital mortality (area under curve >0.80) 3, 4
- Functional outcome prediction: Good at predicting poor functional outcomes (AUC 0.80-0.90) 3
- Component-specific prognostic ability: Some evidence suggests motor and eye components have better prognostic ability than brainstem components 3
Reliability and Validity
- Excellent interrater reliability: Studies show ICC values exceeding 0.90, comparable to GCS 5, 2
- High internal consistency: Cronbach's α > 0.70 across multiple studies 5
- Strong construct validity: Correlates strongly with GCS (Spearman's ρ > 0.90) 5
- Reliable across different providers: Can be reliably applied by healthcare professionals with varying levels of experience and training, including nurses, residents, and specialists 5, 4
Implementation Considerations
When to Use the FOUR Score
- Intubated patients: Particularly valuable when verbal response cannot be assessed 1, 2
- Suspected brainstem pathology: Provides more detailed assessment of brainstem function 1
- Severely unresponsive patients: Better discriminates among patients with minimal responsiveness 1, 2
Potential Limitations
- Confounding factors: Sedation, potent analgesics (e.g., opioids), and neuromuscular blockade can affect assessment 1
- Ventilator modes: Volume assist ventilator modes may confound respiratory component scoring 1
- Experience with the tool: While growing in adoption, experience with FOUR score is still more limited compared to GCS 1