Sonographic Measurement of the Optic Nerve Sheath Diameter to Improve Detection of Elevated Intracranial Pressure

Abstract

Rapid recognition of elevated intracranial pressure (ICP) is essential to avoid brain stem herniation and death. Brain stem herniation is a very serious disorder in which an excess of intracranial pressure causes part of the brain to be squeezed through the foramen magnum at the base of the skull. Increased pressure on the brain stem can lead to blood pressure and breathing problems and brain death, respiratory or cardiac arrest, permanent brain damage, coma and death. The aim of this work was to evaluate the diagnostic accuracy of using Optic Nerve Sheath Diameter (ONSD) measurements to detect elevated ICP compared to computed tomography (CT) brain scanning. A prospective, observational cross-sectional study of 100 randomly selected ICU patients with suspected elevated ICP at Cairo university hospitals and cardiothoracic surgical ICU of the National Heart Institute (NHI), Cairo, Egypt. Optic nerve ultrasonography (US) was performed on all patients; CT brain scanning was chosen as the gold standard for detecting elevated ICP. Results: the cause of elevated ICP, 51.3% of patients were admitted with head trauma P-value = 0.000, clinical signs of elevated ICP, 31.3% of patients developed convulsions and 26.3% showed Cushing reflex (P=0.004 and 0.010 respectively). Besides the Glasgow Coma Scale (GCS), patients with elevated ICP had a mean GCS score of 7 and patients without elevated ICP had mean GCS of 13 (P˂0.001). Regarding ONSD, mean average ONSD was 6 in patients with elevated ICP and 3.1 in patients without elevated ICP (P˂0.01), receiver operating characteristic (ROC) curve analysis revealed that ONSD greater than 4.31 mm was significant in prediction of elevated ICP compared to CT brain scanning with 94.8% sensitivity and 90.11% specificity. Conclusion: patients’ ONSD is a simple bedside technique that can accurately diagnose of elevated ICP compared to CT brain scanning. The diagnostic accuracy of ONSD using a 4.31 mm cut-off value can diagnose of elevated ICP with 94.8% sensitivity and 90.11% specificity.