Aims: To confirm the validity of the method of diagnosing fetal ventriculomegaly at autopsy by measuring cerebral mantle thickness at the frontal lobe and to further evaluate whether taking three measurements at three separate sites is even more reliable.
Methods: The thickness of the cerebral mantle was measured at three sites: the frontal lobe, posterior-frontal lobe and occipital lobe, in 10 human fetuses which were clinically diagnosed by ultrasound to have ventriculomegaly, and in 120 control fetuses. Most fetuses were obtained during the second trimester. The mantle thicknesses were charted against foot length and crown-rump length in each case.
Results: Fetal cerebral mantle thickness was reduced in the three sites examined in eight of ten fetuses with a pre-autopsy diagnosis of ventriculomegaly. The mantle thickness was in the normal range in a growth-restricted fetus of 19 weeks gestational age with trisomy 21, mild ventriculomegaly, hydrops and cerebral oedema, when correlated with crown-rump and foot lengths. In a 32-week growth-retarded fetus with a prenatal ultrasound diagnosis of ventriculomegaly, cerebral mantle thickness was also within the normal range relative to crown-rump and foot lengths.
Conclusion: Measurement at autopsy of cerebral mantle thickness is a reproducible and reliable method of confirming the diagnosis of ventriculomegaly in second trimester fetuses. Fetal cerebral mantle thickness measurement taken at the three sites must be correlated with crown-rump and foot length. In most cases where ventriculomegaly was established, the mantle thickness was reduced in fetuses in all three sites examined. The relative thickness of the cerebral mantle in different areas was often abnormal in the presence of ventriculomegaly. Our study of small numbers of cases also suggested that the method of measurement may not be reliable in some cases where there is only mild ventriculomegaly, cerebral oedema or growth retardation.