What is the FOUR Score in Neurosurgery?
The Full Outline of UnResponsiveness (FOUR) score is a validated neurological assessment tool that evaluates four distinct components—eye response, motor response, brainstem reflexes, and respiration pattern—each scored 0-4 (maximum 16 points), designed specifically to overcome the Glasgow Coma Scale's limitations in intubated patients and to provide detailed brainstem function assessment. 1, 2
Components of the FOUR Score
The FOUR score consists of four clinically distinct categories, each rated from 0 to 4 points:
Eye response component (0-4): Assesses eye opening and tracking, with 4 being eyelids open or opened, tracking or blinking to command, and 0 being no eye opening 1, 3
Motor response component (0-4): Evaluates motor function, with 4 being thumbs-up, fist, or peace sign to command, and 0 being no response to pain or generalized myoclonus 1, 4
Brainstem reflexes component (0-4): Tests pupillary and corneal reflexes plus cough reflex, with 4 being pupil and corneal reflexes present, and 0 being absent pupil, corneal, and cough reflexes 1, 3
Respiration pattern component (0-4): Assesses breathing patterns, with 4 being not intubated and regular breathing pattern, and 0 being breathes at ventilator rate or apnea 1, 4
Key Advantages Over Glasgow Coma Scale
The FOUR score provides superior assessment in intubated patients because it does not rely on verbal responses, making it particularly valuable in neurosurgical ICU settings where most critically ill patients are mechanically ventilated. 2, 5
The FOUR score can differentiate between various states of impaired consciousness, including identifying minimally conscious states through visual pursuit assessment that the GCS cannot detect 6
Brainstem reflex assessment provides strong prognostic information and helps identify different stages of herniation, which the GCS completely lacks 1, 4
The FOUR score can distinguish between patients with the lowest GCS scores (GCS 3), providing additional granularity in severely comatose patients 4
The FOUR score recognizes locked-in syndrome, which the GCS cannot identify 4
Prognostic Value
The FOUR score demonstrates excellent predictive accuracy for mortality and functional outcomes in neurosurgical patients with severely impaired consciousness. 5, 3
For in-hospital mortality prediction, the FOUR score achieves an area under the ROC curve of 0.93 in traumatic brain injury patients, compared to 0.89 for GCS 5
The FOUR score is more robust than GCS in predicting 30-day mortality in neurosurgical patients (AUC 0.768 vs 0.699) 3
The FOUR score demonstrates excellent predictive capacity for mortality and functional outcomes with area under the curve >0.80 in most studies 1
The odds ratio for in-hospital mortality is 0.64 (95% CI 0.46-0.88) for FOUR score, comparable to GCS at 0.63 (95% CI 0.45-0.89) 5
Clinical Applications in Neurosurgery
International consensus recommends systematic use of the FOUR score in comatose patients with acute brain injury, combined with pupillary assessment. 1
The FOUR score provides reproducible measures to chart trends in clinical progress during neurocritical care monitoring 1
It is particularly useful when assessing patients with suspected brainstem pathology or injuries, as it provides detailed brainstem function evaluation 1
The FOUR score helps differentiate between various disorders of consciousness in the neurosurgical population 1
Serial FOUR score assessments should be performed at regular intervals, typically hourly in the acute phase, to detect neurological deterioration 2
Inter-Rater Reliability
The FOUR score demonstrates excellent inter-rater reliability comparable to the GCS:
Inter-rater reliability is excellent with weighted kappa of 0.82, matching the GCS 4
Internal consistency is high with Cronbach's alpha of 0.89 for FOUR score versus 0.85 for GCS 5
Agreement among neuroscience nurses, neurology residents, and neurointensivists is good to excellent 4
Important Limitations and Confounding Factors
Sedation, potent analgesics, and neuromuscular blockade significantly affect FOUR score assessment and must be documented. 1, 2
Volume assist ventilator modes may confound the respiratory component scoring 1
All consciousness scales, including the FOUR score, are confounded by sedation, opioids, and neuromuscular blockade 2
Sedation status must be documented alongside FOUR score assessments using validated scales like the Richmond Agitation Sedation Scale (RASS) 2
Practical Implementation
Assessment should follow a systematic sequence:
Begin with eye response evaluation, followed by motor response, then brainstem reflexes, and finally respiration pattern 1
Document individual component scores rather than just the total, as component profiles provide additional prognostic information 7
Combine FOUR score assessment with pupillary examination (size, reactivity, symmetry), as pupillary responses are strong independent predictors of outcome 2
A significant deterioration (≥2 points in total score) warrants immediate evaluation for new neurological insult 2