Ultrasound-measured optic nerve sheath diameter as a non-invasive tool for screening elevated-pressure from normal-pressure hydrocephalus: a cross-sectional study.

This study evaluates the diagnostic accuracy of ultrasound-measured optic nerve sheath diameter (US-ONSD) in distinguishing elevated-pressure hydrocephalus from normal-pressure hydrocephalus (NP-HCP), with the aim of establishing clinically relevant ONSD thresholds for screening and confirming elevated intracranial pressure (ICP) in clinical practice. This cross-sectional study, conducted at the Neurosurgery Center of Zhujiang Hospital, included patients diagnosed with hydrocephalus. Standardized US-ONSD measurements were performed on all participants, followed by lumbar puncture (LP) to measure ICP. The diagnostic accuracy of US-ONSD measurements was evaluated using receiver operating characteristic (ROC) curve analysis, focusing on sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). A 2 × 2 contingency table was used to determine the optimal ONSD thresholds for screening and confirming elevated ICP. A total of 42 hydrocephalus patients were included in this study: 22 patients with elevated-pressure hydrocephalus and 20 with normal-pressure hydrocephalus. The mean ONSD was significantly higher in the elevated-pressure group compared to the normal-pressure group (5.60 mm vs. 4.70 mm, p < 0.001). The overall cohort had a mean age of 53.6 years (SD 15.7), with 20 males (47.6%). The average weight, height, and body mass index (BMI) were 59.0 kg (SD 9.8), 163.2 cm (SD 7.3), and 22.1 kg/m² (SD 3.2), respectively. Receiver operating characteristic (ROC) analysis demonstrated excellent diagnostic performance (AUC = 0.957, 95% CI: 0.888-1.000). The optimal ONSD thresholds for excluding elevated ICP were 4.82 mm (NPV = 1), and for confirming elevated ICP were 5.75 mm (PPV = 1), thereby maximizing sensitivity and specificity. US-ONSD is a reliable, non-invasive method for detecting elevated ICP in patients with hydrocephalus. We propose two ONSD threshold values for clinical application: 4.82 mm for excluding elevated ICP and 5.75 mm for confirming it. These thresholds provide a practical and effective approach for screening and confirming elevated ICP, particularly in scenarios where invasive procedures, such as lumbar puncture, are not feasible or are contraindicated. Further multi-center studies are needed to validate these thresholds and optimize their clinical utility.