Evaluation of the Combined Use of Optic Nerve Sheath Diameter and the FOUR Score in Predicting Brain Death in Patients with Severe Brain Injury Admitted to the Intensive Care Unit

Background Brain death is a catastrophic outcome of severe brain injury, most commonly associated with progressive intracranial hypertension. Early identification of patients at risk for brain death remains challenging. Optic nerve sheath diameter (ONSD), reflecting intracranial pressure, and the Full Outline of UnResponsiveness (FOUR) score, assessing neurological function, have been proposed as prognostic tools; however, evidence regarding their combined use is limited. Objective To evaluate the predictive value of ONSD and the FOUR score, individually and in combination, for the development of brain death in patients admitted to the intensive care unit with severe brain injury. Methods This single-center, retrospective study included adult patients with severe neurological impairment (Glasgow Coma Scale ≤ 7). ONSD was measured on admission cranial computed tomography scans. Clinical data and neurological scores were recorded. A modified FOUR score incorporating ONSD as a fifth parameter was developed. The primary outcome was the development of brain death during intensive care follow-up. Results Among 316 patients, those who developed brain death had significantly lower GCS and FOUR scores and significantly higher ONSD values (p < 0.001). An ONSD cutoff value of > 5.62 mm demonstrated excellent discriminative performance for predicting brain death (AUC: 0.992; sensitivity 98.65%, specificity 97.52%). The modified FOUR score showed high sensitivity but limited specificity, suggesting a screening rather than a definitive discriminative role. In multivariable analysis, ONSD was the only independent predictor of brain death (OR: 345.7; p < 0.001). Conclusions ONSD is a strong and independent predictor of brain death in patients with severe brain injury. While the FOUR score provides valuable clinical information, its prognostic utility appears enhanced when combined with objective markers of intracranial hypertension. The modified FOUR score may serve as a complementary screening tool, whereas ONSD offers robust discriminatory power. Integrating clinical neurological assessment with imaging-based parameters may improve early risk stratification for brain death.