# Bedside Ultrasonographic Measurement of Optic Nerve Sheath Diameter for Assessing Increased Intracranial Pressure: An Observational Study

## TL;DR

This study shows that measuring optic nerve sheath diameter with ultrasound is a reliable way to detect high brain pressure in traumatic brain injury patients.

## Contribution

The study demonstrates high diagnostic accuracy of bedside optic nerve sheath diameter ultrasound for detecting elevated intracranial pressure in TBI patients.

## Key findings

- ONSD measurements showed 95.5% sensitivity and 93.9% specificity for detecting elevated ICP.
- An ONSD greater than 5.5 mm was strongly linked to poor neurological outcomes.
- ONSD values increased with TBI severity, showing a clear correlation.

## Abstract

Background

Traumatic brain injury (TBI) is a leading cause of disability and mortality, particularly in resource-limited settings where advanced neuromonitoring tools are often unavailable. Elevated intracranial pressure (ICP) is a serious and potentially life-threatening complication of TBI. Traditional methods for monitoring ICP are invasive, expensive, and require specialized expertise. Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) offers a noninvasive, real-time, and radiation-free alternative for assessing ICP.

Objective

This study aimed to evaluate the diagnostic accuracy of bedside ONSD measurement in detecting elevated ICP among neurotrauma patients, using CT imaging as the reference standard. Additionally, it explored the relationship between ONSD measurements, TBI severity, and neurological outcomes.

Methods

A prospective observational study was conducted on 100 adult patients with TBI, in whom bilateral ONSD measurements were obtained using a high-frequency linear ultrasound probe. Based on CT scan findings, patients were classified as having either raised or normal ICP. Statistical analyses included sensitivity, specificity, positive and negative predictive values, receiver operating characteristic curve analysis, and logistic regression to assess the diagnostic and prognostic utility of ONSD.

Results

Raised ICP was observed in 67% of patients, most of whom had moderate to severe TBI. ONSD values increased with injury severity: mild (4.53 ± 0.14 mm), moderate (5.24 ± 0.15 mm), and severe (5.90 ± 0.25 mm). A cutoff value of 5.2 mm demonstrated 95.5% sensitivity, 93.9% specificity, and an area under the curve of 0.96. An ONSD greater than 5.5 mm was strongly associated with poor neurological outcomes (Glasgow Outcome Scale scores 1-3), with an OR of 4.6 (p < 0.001).

Conclusions

Bedside ultrasonographic measurement of ONSD is a reliable and accurate method for detecting elevated ICP in TBI patients. It correlates strongly with both injury severity and clinical outcomes, making it a valuable tool in emergency and intensive care settings. Further studies comparing this technique with invasive monitoring methods and evaluating long-term outcomes are warranted.