OC07.09: Sonographic evaluation of optic nerve sheath diameter as an indicator of raised intracranial pressure in pre‐eclamptics in a Nigerian population

Raised intracranial pressure (ICP) is associated with poor outcome after brain injury, but is difficult to detect without invasive devices. As a part of the central nervous system, the optic nerve is surrounded by a dural sheath, and the subarachnoid space surrounding the optic nerve is subject to the same pressure changes as the intracranial compartment. Distension of the optic nerve sheath reflects an increase in cerebrospinal fluid (CSF) pressure and can be used to estimate the risk of raised ICP. Ocular sonography or brain magnetic resonance imaging (MRI) enables valid measurement of the distension of the dural sheath surrounding the optic nerve. An optic nerve sheath diameter greater than 5.8mm is likely to be associated with raised ICP. This non-invasive estimate of ICP may detect patients at risk, help make decisions regarding the placement of invasive ICP devices and allow the selection of patients for transfer to specialist centres.

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How accurate is ultrasound of the optic nerve sheath diameter performed by inexperienced operators to exclude raised intracranial pressure?

South African Journal of Radiology ◽

10.4102/sajr.v19i1.745 ◽

2015 ◽

Vol 19 (1) ◽

Cited By ~ 1

Author(s):

G. J. Du Toit ◽

D. Hurter ◽

M. Nel

Keyword(s):

Optic Nerve ◽

Intracranial Pressure ◽

Lumbar Puncture ◽

Predictive Value ◽

Optic Nerve Sheath Diameter ◽

Optic Nerve Sheath ◽

Ultrasound Measurement ◽

Raised Intracranial Pressure ◽

Cross Sectional ◽

Nerve Sheath

Background: It has been well documented that ultrasound measurement of the optic nerve sheath diameter performed by an experienced operator shows good correlation with raised intracranial pressure, irrespective of the cause. Objective: To establish the accuracy of this technique performed by inexperienced operators.Method: A prospective analytical cross-sectional study was conducted. All patients ≥18 years of age who presented at our medical casualty and emergency departments with suspected meningitis were enrolled in the study. All patients were evaluated with the use of optic nerve sheath diameter ultrasound with or without computed tomography brain scan prior to lumbar puncture. Lumbar puncture opening pressure measurements were compared with the ultrasound measurements.Results: A total of 73 patients were enrolled in the study, of whom 14 had raised intracranial pressure. The study had a sensitivity of 50% (95% confidence interval (CI) 26.8%–73.2%) and specificity of 89.8% (95% CI 79.5%–95.3%) with a positive predictive value of 54.8% (95% CI 29.1%–76.8%) and negative predictive value of 88.3% (95% CI 77.8%–94.2%). The likelihood ratio of a positive test was 4.92 (95% CI 1.95–11.89) and that of a negative test 0.56 (95% CI 0.29–0.83). Cohen’s kappa value was 0.41 which indicates a moderate agreement. The receiver operating characteristic (ROC) curve had an area under the curve (AUC) of 0.73 (95% CI 0.51–0.95). Conclusion: Ultrasound measurement of the optic nerve sheath diameter can be used to exclude raised intracranial pressure, even in the hands of inexperienced operators.

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