UTILITY OF POINT-OF-CARE OF CARE ULTRASOUND TO MEASURE OPTIC NERVE SHEATH DIAMETER FOR DIAGNOSING RAISED INTRACRANIAL PRESSURE IN THE EMERGENCY DEPARTMENT

Abstract

Background: Elevated intracranial pressure (ICP) is a neurological emergency that demands early recognition and prompt intervention to prevent irreversible brain injury. Conventional diagnostic methods such as invasive catheter monitoring and computed tomography (CT) are often limited by accessibility, time constraints, and procedural risks. Point-of-care ultrasound (POCUS) assessment of the optic nerve sheath diameter (ONSD) provides a rapid, non-invasive bedside alternative for detecting raised ICP, particularly in emergency and resource-limited settings.

Objective: To determine the diagnostic accuracy of ultrasonographic ONSD measurement using POCUS in detecting raised ICP compared with CT findings in the emergency department (ED).

Methods: This prospective validation study was conducted over two years in the ED of Combined Military Hospital, Rawalpindi. A total of 125 adult patients presenting with clinical suspicion of raised ICP were enrolled. Bilateral ONSD was measured 3 mm posterior to the globe using a high-frequency linear ultrasound probe (3–13 MHz) before CT imaging. A cutoff value of >5.6 mm was defined as indicative of raised ICP. CT findings served as the reference standard. Diagnostic metrics including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy were computed, and receiver operating characteristic (ROC) analysis was performed.

Results: The mean ONSD was 6.3 ± 0.68 mm. CT confirmed raised ICP in 100 patients (80%), while elevated ONSD was observed in 109 (87.2%). The ONSD measurement demonstrated a sensitivity of 95%, specificity of 55%, PPV of 83%, NPV of 84%, and overall diagnostic accuracy of 83%. The area under the ROC curve was 0.82, indicating strong discriminative ability. The most frequent intervention among patients with raised ICP was intravenous mannitol administration (53.6%).

Conclusion: POCUS-based ONSD measurement offers a reliable, rapid, and non-invasive tool for early detection of raised ICP in emergency settings. Its high sensitivity supports its utility as an effective screening modality where immediate neuroimaging is not feasible. However, moderate specificity necessitates cautious interpretation and clinical correlation to avoid overestimation. Standardization of technique, operator training, and population-specific cutoff validation are recommended for optimal diagnostic performance.