Patients commonly, for one clinical reason or another, have some degree of impaired consciousness. Our efforts are directed to evaluate the depth of consciousness to properly manage these patients. One of our duties is also to predict mortality outcome in patients with impaired consciousness. In our study, we evaluated consciousness and depth of coma in patients with brain injury in the prehospital setting. We focused specifically on comparing two coma scales: the GCS (Glasgow Coma Scale) and the FOUR score (Full Outline of UnResponsiveness).
Since 1974 , when the GCS was introduced, the GCS has been widely used in the prehospital setting. In 2005, the FOUR score  was proposed to reduce some limitations of GCS assessment. Currently, the FOUR score is mostly employed in intensive and neurological care units.
The advantages of the FOUR score have been assessed by Wijdicks et al. , especially in neurologically critically ill patients who are intubated. When we compared the GCS and FOUR scores, we noticed a key difference: the verbal response is not an intrinsic part of the FOUR score; taking this into consideration, the FOUR score is fully useful in intubated patients . Intubation is a common procedure in the field, in the emergency department, in the ICU and in the prehospital setting. The FOUR score tests essential brainstem reflexes and provides information about stages of brainstem injury that is unavailable with the GCS. The FOUR score can distinguish a locked-in syndrome and a possible vegetative state  and includes signs suggesting uncal herniation . The evaluation of the respiratory patterns in the FOUR score may also add information about the presence of a respiratory drive . Studies also show that in-hospital mortality between scales was higher for the lowest total FOUR scores when compared with the GCS scores . Conclusions obtained in previous studies have shown that the FOUR score is an accurate predictor of outcome mortality in TBI patients, has some advantages over the GCS  and can be performed in a variety of ICU contexts. After all, the FOUR score is easily taught, simple to administer, and provides essential neurologic information that allows for an accurate assessment of patients with altered consciousness with excellent interrater agreement among medical intensivists . The FOUR score might be a better prognostic tool of ICU mortality than the GCS, most likely because it integrates brainstem reflexes and respiration . Other studies have shown the predictive value of the FOUR score on admission of patients after moderate and severe TBI. These studies shown also that the predictive ability for the primary outcome of mortality 2 weeks after injury was no better than that of the GCS score . For nontraumatic comatose patients, different parameters as predictors of mortality in the prehospital environment were also studied .
Analyses performed between GCS and FOUR score scales in the hospital environment have demonstrated that GCS was missing key essential elements of a comprehensive neurological examination for comatose patients . In the same study, it was confirmed that the FOUR score maintained simplicity and, at the same time, provided far better information . Other previous studies have demonstrated that GCS and FOUR scores show comparable results in the assessment of patients with traumatic brain injury. These data show that there were excellent statistical correlations between the two scoring systems. Additionally, the FOUR score provides better details regarding the neurological status of the patient. The results can be considered clinically relevant because of the strong statistical association obtained as well as the agreement in the literature . Overall, there are currently multiple scores used to determine the prognosis of patients in intensive care units. However, a scoring system should be simple, reliable, and predictive of morbidity and mortality.
Due to the different categories of scores, the FOUR score is more effective in evaluating patients who are unconscious and dependent on mechanical ventilation. Prospective studies with larger cohorts of patients treated in various intensive care units for longer durations are needed to evaluate whether the application of these scales influences functional and cognitive outcomes .
In addition, further comparative neurological outcome studies show also that the mortality of patients admitted to the ICU was significantly higher, when the GCS or the FOUR score was used. Discrimination was fair for both scores, but the FOUR score was superior to the GCS. Calibration was better for the FOUR score than for the GCS in ICU. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were also better for the FOUR score than for the GCS score. A good correlation was observed between the two scores .
A comprehensive overview of the relationship between a patient’s FOUR score and outcome is still lacking. A recent study on the FOUR score overall showed that the FOUR score has a close relationship to in-hospital mortality and poor functional outcome in patients with impaired consciousness. This research also claims that there was insufficient evidence to determine whether performance was modified in different groups, and there was some suggestion that the assessment of brainstem reflexes and respiratory patterns made less contribution than eye and motor scores .
In the present study, our data showed only a marginal statistically significant difference in terms of correct prediction of mortality outcome 24 hours after the injury, specifically between the GCS 1 and FOUR 2 model scales (P = 0.039) and between the GCS 1 and FOUR 3 model scales (P = 0.039). We found no statistically significant differences in the Youden index or area under the ROC curve after 24 hours, no statistically significant differences one month after the injury, and no statistically significant differences three months after the injury.
We think that we must gain a better understanding of the anatomical and pathophysiological pathways that are not evidenced by certain GCS and FOUR score numbers. The next level of research should be focused on the comparison between the obtained GCS and FOUR score data measurements and the anatomical substrate changes revealed by a diagnostic tool such as CT scan of the head and fMRI of the brain. With these data, we could obtain the accurate sub-anatomical and clinical information needed to perform a specific invasive therapy to lead to a far better outcome for the patient.