Predicting Computed Tomography Scan-Determined Elevated Intracranial Pressure by Ultrasonographic Measurement of Optic Nerve Sheath Diameter: A Prospective Observational Study.

Introduction Traumatic brain injury (TBI) is a major public health problem and is associated with short- and long-term adverse clinical outcomes, including disability and death. Neuroimaging with computed tomography (CT) of the brain is used to detect evidence of increased intracranial pressure (ICP) in settings where invasive ICP monitoring is not practiced. Transorbital ultrasound (US) to measure the optic nerve sheath diameter (ONSD) is a non-invasive method for detecting elevated intracranial pressure (EICP). The present study was undertaken to assess the utility of transorbital US to measure ONSD and predict EICP in individuals with moderate-to-severe TBI compared with computed tomography (CT)-detected EICP. Materials and methods This prospective observational study was conducted at the Department of Critical Care Medicine in a tertiary care hospital in eastern India. This study prospectively recruited 110 patients aged ≥ 18 years with moderate-to-severe TBI who were admitted to the critical care unit (CCU) between July 1, 2021, and December 31, 2022. EICP was defined by ONSD ≥5.5 mm. Results A total of 110 patients with moderate-to-severe TBI were recruited during the study period. The recruited patients were divided into two groups based on the CT evidence of EICP: 1. CT positive (CTP) group: patients with evidence of EICP on CT scan; and 2. CT negative (CTN) group: patients with no evidence of EICP on CT imaging. A CT scan of the brain detected EICP in 58% of the patients (n = 64). An increased ONSD (≥ 5.5 mm) by transorbital US was noted in 69% (n = 76) of the cohort, and a CT brain characteristic of EICP was present in 71% (n = 54). Using the ONSD assessment, 10 patients with positive CT brain features of EICP were missing. Of the patients with moderate-to-severe TBI, a significantly higher proportion of patients with CT-detected EICP had ONSD measurement ≥ 5.5 mm compared with the CTN group. Furthermore, the mean ONSD of the CTP group (5.57 mm) was significantly greater than that of the CTN group (5.20 mm). The CTN group exhibited a significantly greater survival rate, 68.5% (n = 44) of the CTP group and 37% (n = 17) of the CTN group died before discharge. ONSD with a cut-off value of ≥ 5.5 mm had a sensitivity of 84% and a specificity of 65% with positive predictive value and negative predictive value of 70% and 69%, respectively, for predicting CT-determined EICP. Conclusion Our study demonstrated that measurement of ONSD by transorbital ultrasound is a sensitive tool for predicting EICP in patients with moderate-to-severe TBI in the critical care unit. CT evidence of EICP is a risk factor for reduced survival in patients with moderate-to-severe traumatic brain injury.