Ultrasound Nomograms of the Fetal Optic Nerve Sheath Diameter

Abstract

Objective To construct prenatal age-specific reference intervals for sonographic measurements of the optic nerve sheath diameter (ONSD) during gestation in normal fetuses.

Materials and Methods Prospective cross-sectional study of fetuses assessed in antenatal ultrasound units between 2010 and 2014. The examination was based on a technique for the sonographic assessment of ONSD previously published by our group. The mean values and SDs of the ONSD were modeled as a function of the gestational week by curve estimation analysis based on the highest adjusted R2 coefficient. Repeatability tests were performed to assess intraobserver variability and interobserver agreement.

Results During the study period 364 healthy fetuses were enrolled. The mean values for the ONSD varied from 0.6 mm at 15–16 weeks to 2.8 mm at 37–38 weeks. The ONSD grows in a linear fashion throughout gestation, with a quadratic equation providing an optimal fit to the data (adjusted R2 = 0.957).

Conclusion Sonographic age-specific references for the fetal ONSD are presented. This data may assist in the decision-making process in fetuses with a suspected increase in intracranial pressure, or anomalies affecting the development of optic stalks, such as optic hypoplasia and septo-optic dysplasia.

Zusammenfassung

Ziel Bestimmung von pränatalen, altersbezogenen Referenzintervallen für sonografische Messungen des Durchmessers der Sehnervscheide („optic nerve sheath diameter“ = ONSD) bei normalen Feten über die gesamte Schwangerschaft.

Material und Methoden Prospektive Querschnittsstudie an Feten, die zwischen 2010 und 2014 in Zentren für Pränataldiagnostik beurteilt wurden. Die Untersuchung basierte auf einer zuvor von unserer Gruppe publizierten Methode zur sonografischen Bewertung des ONSD. Die Mittelwerte und SDs des ONSD wurden als Funktion der Schwangerschaftswoche durch Kurvenschätzungsanalyse basierend auf dem höchsten bereinigten R2-Koeffizienten dargestellt. Für die Bewertung der Intraobserver-Variabilität und Interobserver-Übereinstimmung wurden Reproduzierbarkeitsteste durchgeführt.

Ergebnisse Im Studienzeitraum wurden 364 gesunde Feten aufgenommen. Die Mittelwerte für den ONSD variierten von 0,6 mm in der 15. –16. Woche bis 2,8 mm in der 37. –38. Woche. Der ONSD nimmt während der Schwangerschaft linear zu, wobei eine quadratische Gleichung eine optimale Anpassung an die Daten liefert (bereinigter R2 = 0,957).

Schlussfolgerung Es wurden sonografische altersspezifische Referenzwerte für den fetalen ONSD vorgestellt. Diese Daten können bei Feten mit Verdacht auf intrakraniellen Druckanstieg oder bei Anomalien, die die Bildung der Augenstiele beeinträchtigen, wie z. B. optische Hypoplasie und septo-optische Dysplasie, zur Entscheidungsfindung beitragen.

Key words

fetus - brain - optic nerve sheath diameter - ultrasound - septo-optic dysplasia

^* These authors contributed equally

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