Anatomical subgroup analysis of the MERIDIAN cohort: Ventriculomegaly

Objective

To assess the contribution of in utero magnetic resonance (iuMR) imaging in fetuses diagnosed with ventriculomegaly as the only abnormal intracranial finding on antenatal ultrasonography (USS) in the MERIDIAN cohort.

Methods

We report a sub-group analysis from the MERIDIAN study, of cases of fetal ventriculomegaly diagnosed on USS who then had iuMR imaging within 2 weeks of USS and for whom outcome reference data were available. The diagnostic accuracy of USS and iuMR are reported in relation to the severity of ventriculomegaly. We also study the difference in measurements of trigone size on the two imaging methods and present the clinical impact of adding iuMR to the diagnostic pathway.

Results

USS failed to detect 31 additional brain abnormalities other than ‘ventriculomegaly’ in the subgroup of 306 fetuses, giving an overall diagnostic accuracy of 89.9% for USS, whilst iuMR correctly detected 27 giving a diagnostic accuracy of 98.4% (statistically significant p < 0.0001). There were other brain abnormalities in 14/244 of fetuses with mild ventriculomegaly on USS (diagnostic accuracy 94.3%), and iuMR correctly diagnosed 12 of those (diagnostic accuracy 98.8%). All of those results reached statistical significance in favour of iuMR. There was a close agreement between the size of trigones measured on USS and on iuMR, with categorical differences in only 16% of cases. iuMR did not systematically over-estimate trigone size, as suspected before the study commenced. Complete prognosis data were available in 295/306 fetuses and the prognosis category changed after iuMR in 69/295 (23.4%) cases. The overall effect of iuMR on clinical management was considered to be either ‘significant’, ‘major’ or ‘decisive’ in 76/295 (25.8%) cases.

Conclusion

Our data suggest that any woman whose fetus has ventriculomegaly as the only intracranial finding on USS should be offered an adjuvant investigation of iuMR for further evaluation.