Measurement of the Optic Nerve Sheath Diameter in Children: Comparison Between Transbulbar Sonography and Magnetic Resonance Imaging

Abstract

Purpose: To evaluate the accuracy of measurements of the optic nerve sheath diameter (ONSD) in children by comparing transbulbar sonography with magnetic resonance imaging (MRI).

Materials and Methods: 65 children (age: 3 mo– 17y; mean age: 11.3y) underwent MR imaging of the brain including a heavily T 2-w sequence of the orbit and transbulbar sonography using a 17 MHz linear array transducer. Measurements of the ONSD were performed retrospectively by two experienced readers and all images were evaluated regarding the image quality. Bland-Altman Plots were produced to assess the accuracy of measurements. The correlation between readers and between MR imaging and transbulbar sonography was calculated by the concordance correlation coefficient (CCC).

Results: Overall the mean values of the ONSD for MRI (5.86 ± 0.66 mm) and transbulbar sonography (5.86 ± 0.71 mm) were identical. There was a high correlation between readers for measurements of the ONSD both for transbulbar sonography (CCC = 0.93) as well as for MRI (CCC = 0.9). Comparing the measurement values between transbulbar sonography and MRI, the correlation of ONSD values was good to moderate with a high dependency on image quality (CCC [0.31, 0.68]).

Conclusion: We were able to demonstrate that the ONSD values of transbulbar sonography in children correlate well with MRI if the relevant anatomic structures are depicted and the measuring points are set correctly. Based on the findings of our study, it seems necessary to define normal and cut-off values for the ONSD in children again to finally assess the clinical relevance of the ONSD as a noninvasive parameter for the evaluation of intracranial pressure.

Zusammenfassung

Ziel: Evaluation der Genauigkeit von Messungen des Nervenscheidendurchmessers des Nervus opticus (ONSD) bei Kindern durch den Vergleich zwischen transbulbärer Sonografie und Magnetresonanztomografie (MRT).

Material und Methoden: 65 Kinder (Altersspanne: 3 Monate – 17 Jahre; Mittelwert: 11,3 Jahre) erhielten eine MRT-Untersuchung des Kopfes inklusive einer stark T 2-gewichteten Sequenz der Orbita und eine transbulbäre Sonografie mit einem 17 MHz-Linearschallkopf. Die Messungen des ONSD erfolgten retrospektiv durch zwei erfahrene Untersucher und alle Bilder wurden hinsichtlich der Bildqualität beurteilt. Mittels Bland-Altman-Plots wurde die Messgenauigkeit ermittelt. Die Korrelation zwischen den Betrachtern und zwischen den Messergebnissen aus MRT und transbulbärer Sonografie wurde durch concordance correlation coefficients (CCC) bestimmt.

Ergebnisse: Insgesamt fand sich eine exakte Übereinstimmung der Mittelwerte des ONSD zwischen MRT (5,86 ± 0,66 mm) und transbulbärer Sonografie (5,86 ± 0,71 mm). Es bestand eine hohe Korrelation der Messungen des ONSD zwischen den Betrachtern sowohl für die transbulbäre Sonografie (CCC = 0,93) als auch die MRT (CCC = 0,9). Vergleicht man die Werte der ONSD-Messungen zwischen transbulbärer Sonografie und MRT, ergab sich eine mittlere bis gute Korrelation mit deutlicher Abhängigkeit der Ergebnisse von der Bildqualität (CCC [0.31, 0.68]).

Schlussfolgerung: Wir konnten zeigen, dass die ONSD-Messwerte der transbulbären Sonografie gut mit denen der MRT korrelieren, wenn die relevanten anatomischen Strukturen dargestellt sind und die Messpunkte korrekt gesetzt werden. Basierend auf den Ergebnissen der Studie erscheint es notwendig, nochmals Norm- und Grenzwerte für den ONSD bei Kindern zu bestimmen, um die klinische Bedeutung des ONSD bei der Hirndruckdiagnostik abschließend beurteilen zu können.

Key words

eye - MR imaging - ultrasound - anatomy

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