FOUR score
The FOUR score, formally known as the Full Outline of UnResponsiveness score, is a standardized clinical tool designed to assess the level of consciousness in patients with impaired responsiveness, such as those in coma within intensive care settings. It evaluates four key components—eye response, motor response, brainstem reflexes, and respiration—each graded on a scale from 0 (worst) to 4 (best), resulting in a total score ranging from 0 to 16, where higher scores indicate better neurological function. Developed in 2005 by Eelco F. M. Wijdicks and colleagues at the Mayo Clinic as an alternative to the Glasgow Coma Scale (GCS), the FOUR score addresses limitations of the GCS, including the inability to score verbal responses in intubated patients and the lack of assessment for brainstem function or respiratory patterns. Unlike the GCS, which totals 3 to 15 and relies on eye, verbal, and motor components, the FOUR score offers greater neurological detail, enabling detection of conditions like locked-in syndrome, vegetative states, and brain herniation stages.[1] Initial validation involved prospective evaluation in 120 intensive care unit (ICU) patients, demonstrating excellent interrater reliability comparable to the GCS (weighted kappa of 0.82 for both scales). Subsequent studies have confirmed the FOUR score's reliability and validity across diverse populations, including medical ICU patients, with interrater agreement consistently high (kappa values exceeding 0.6 in most analyses) and strong correlation to GCS outcomes (r > 0.8).[2] It shows superior predictive power for mortality and poor functional outcomes in neurocritical care, outperforming the GCS in intubated cases and at the lowest score levels (e.g., 89% in-hospital mortality at FOUR score 0 versus 71% at GCS 3).[2] A 2020 systematic review of 42 studies involving over 4,500 patients highlighted its advantages in brainstem and respiration evaluation, supporting its widespread use in critical care for serial monitoring and prognostication.[1]Overview
Definition and Purpose
The FOUR (Full Outline of UnResponsiveness) score is a standardized clinical tool designed to assess the level of consciousness in patients with severe neurological impairment, particularly those in coma or unable to communicate verbally.[3] It provides an objective evaluation of coma depth by examining key neurological functions, enabling healthcare providers to monitor disease progression, guide treatment decisions, and predict outcomes in critical care settings.[2] The primary purpose of the FOUR score is to offer a reliable measure of neurological status in patients with brain injuries, acute neurological conditions, or respiratory failure, where traditional verbal-based assessments may be infeasible. Unlike earlier scales, it avoids reliance on verbal responses, making it particularly valuable for intubated or sedated individuals in intensive care units (ICUs), emergency departments, and neurocritical care environments.[4] This focus ensures applicability across diverse patient populations with impaired consciousness, including non-traumatic etiologies like stroke or metabolic disorders.[5] Key features of the FOUR score include its 16-point scale, ranging from 0 (indicating the deepest level of coma) to 16 (full responsiveness), derived from four distinct domains: eye response, motor response, brainstem reflexes, and respiration. Each domain is scored from 0 to 4, allowing for a granular yet straightforward assessment that captures subtle changes in brainstem function and respiratory patterns often overlooked in other tools.[3] Developed to address limitations in existing coma scales, such as the Glasgow Coma Scale (GCS), the FOUR score enhances accuracy in detecting conditions like locked-in syndrome and brain herniation without requiring patient cooperation.[2]Development and History
The FOUR score was developed by Dr. Eelco F. M. Wijdicks and colleagues at the Mayo Clinic in Rochester, Minnesota, as a novel tool for assessing consciousness in comatose patients.[6] First described in 2005 in a validation study published in the Annals of Neurology, the scale was designed to address key limitations of the Glasgow Coma Scale (GCS), including its inability to evaluate verbal responses in intubated or sedated patients and its omission of brainstem reflexes and respiratory patterns.[6] The developers aimed to create a simple yet comprehensive system that could be applied reliably across various clinical scenarios, particularly in neurocritical care settings involving mechanically ventilated individuals.[6] Initial testing occurred prospectively in the neurocritical care unit at Mayo Clinic, involving 120 intensive care unit patients with acute neurological conditions.[6] Assessments were performed by neuroscience nurses, neurology residents, and neurointensivists, demonstrating excellent inter-rater reliability for the total FOUR score (weighted kappa = 0.82), comparable to that of the GCS.[6] The study confirmed the scale's ability to provide detailed neurological information, such as identifying locked-in syndrome and stages of brainstem herniation, while correlating well with in-hospital mortality outcomes.[6] Following its introduction, the FOUR score underwent rapid evolution through targeted adaptations and validations in diverse contexts. In 2008, researchers at Mayo Clinic validated its use in the emergency department by non-neurology staff, highlighting its feasibility and equivalence to the GCS in predicting outcomes among patients with altered mental status. Pediatric adaptations emerged shortly thereafter, with a 2009 study confirming the scale's inter-rater reliability and predictive validity in children, allowing for age-appropriate assessments in comatose pediatric populations. By 2010, international validations had begun, including a 2009 study in Thailand that demonstrated the FOUR score's reliability and prognostic utility in emergency settings outside the United States.[7] Subsequent research, including a 2020 systematic review of 42 studies involving over 4,500 patients, has affirmed the FOUR score's reliability, validity, and advantages in brainstem and respiration evaluation across global settings.[1]Components of the FOUR Score
Eye Response
The eye response component of the FOUR score assesses a patient's oculomotor function and level of arousal by evaluating eyelid opening and visual tracking in response to stimuli, contributing 0 to 4 points to the total score.[8] This subscale provides a nuanced evaluation of cortical and brainstem integrity, particularly in patients with impaired consciousness.[9] The scoring criteria are as follows:- 4 points: Eyelids open or opened, tracking, or blinking to command (recognizes locked-in syndrome with vertical eye movements).[8]
- 3 points: Eyelids open but not tracking.[8]
- 2 points: Eyelids closed but open to loud voice.[8]
- 1 point: Eyelids closed but open to pain.[8]
- 0 points: Eyelids remain closed with pain.[8]
Motor Response
The motor response component of the FOUR score evaluates the best motor response in the upper extremities of comatose patients, using verbal commands or painful stimuli such as temporomandibular joint or supraorbital pressure, to assess the integrity of motor pathways. This component is scored on a 0-to-4 scale, where higher scores indicate more intact motor function and lower scores reflect greater impairment. The detailed scoring criteria for motor response are as follows:| Score | Criteria |
|---|---|
| 4 | Thumbs-up, fist, or peace sign (purposeful response to command) |
| 3 | Localizing to pain (patient touches the examiner's hand or site of stimulus) |
| 2 | Flexion response to pain (withdrawal or decorticate posturing) |
| 1 | Extension response to pain (decerebrate posturing) |
| 0 | No response to pain or generalized myoclonus status epilepticus |
Brainstem Reflexes
The brainstem reflexes component of the FOUR score evaluates the integrity of the brainstem through assessment of pupillary light response, corneal reflex, and cough reflex, targeting functions in the mesencephalon, pons, and medulla oblongata.[8] This component is scored on a scale from 0 to 4 points, with higher scores indicating preserved reflex activity and lower scores reflecting progressive brainstem dysfunction.[8] The specific scoring criteria are as follows:- 4 points: Both pupils and corneal reflexes are present, demonstrating intact midbrain and pontine pathways.
- 3 points: One pupil is dilated and fixed, often signaling ipsilateral oculomotor nerve compression due to transtentorial herniation.
- 2 points: Either pupillary or corneal reflexes are absent, indicating partial brainstem impairment.
- 1 point: Both pupillary and corneal reflexes are absent, suggesting more advanced dysfunction.
- 0 points: Pupillary, corneal, and cough reflexes are all absent, with the cough reflex tested via tracheal suctioning only if the other reflexes are already lost; this level points to severe medullary involvement.[8]