Original Research

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

G. J. du Toit, D. Hurter, M. Nel
South African Journal of Radiology | Vol 19, No 1 | a745 | DOI: https://doi.org/10.4102/sajr.v19i1.745 | © 2015 G. J. du Toit, D. Hurter, M. Nel | This work is licensed under CC Attribution 4.0
Submitted: 14 October 2014 | Published: 07 August 2015

About the author(s)

G. J. du Toit, Department of Clinical Imaging Sciences, University of the Free State, South Africa
D. Hurter, Department of Radiology, Kimberley Hospital Complex, Kimberley, South Africa, South Africa
M. Nel, Department of Biostatistics, University of the Free State, South Africa


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Abstract

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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