Assessment of sulcation of the fetal brain in cases of isolated agenesis of the corpus callosum using in utero MR imaging

Abstract

Background and purpose: There is gathering evidence to suggest that agenesis of the corpus callosum is associated with delayed fetal sulcation; it is possible that the corpus callosum facilitates normal gyral development. In this paper we sought to confirm whether delayed sulcation is found in fetuses with isolated agenesis of the corpus callosum as judged by in utero MR imaging.

Materials and methods: Retrospective analysis of 20 fetuses with isolated corpus callosum agenesis investigated by in utero MR imaging and 20 aged-matched normal fetuses was performed in the second or third trimester. All fetuses were singleton pregnancies with known gestational age, imaged on a 1.5T superconducting MR system. Estimation of sulcation maturity was made with reference to a standard atlas and subgroup analysis of earlier gestation (group 1, 21-26 weeks) and later gestation (group 2, 30-34 weeks) fetuses was performed.

Results: Group 1 (n = 12) did not show a statistically significant difference between the 2 subgroups (P = .44) in terms of sulcation. A significant difference was demonstrated in the later gestation, group 2 (n = 8) fetal analyses; mean difference between consensus and actual gestation for normal fetuses was 0.9 weeks (SD of 1.5 weeks) versus -0.5 weeks (SD of 1.1 weeks) for the agenesis of corpus callosum cases (P = .046), suggestive of delayed sulcation in callosal agenesis.

Conclusions: Delayed sulcation encountered in third trimester fetuses with agenesis of the corpus callosum may be seen and does not in itself imply an additional brain abnormality.

Fig 1.

Results displayed by using a Bland-Altman plot (A) normal subgroup. B, ACC subgroup, demonstrating average gestational age (weeks) versus mean difference (weeks). The mean and mean ± 2 SD reference lines are demonstrated.

Fig 2.

Axial (A) and (B) coronal plane iuMR of a normal 24 week fetus (group 1); C (axial) and D (coronal) represent an aged-matched ACC case. No discernable difference of the surface sulcal pattern is present. The lateral sulcus is demonstrated on B and D (black arrow).

Fig 3.

In utero MR of 31 week gestation fetuses; A (axial) and B (coronal) views of a normal fetus are shown; C and D represent an aged-matched ACC case. This case demonstrates relative sulcation delay with ACC, most obvious within the temporal lobes on coronal imaging where delay in formation of the superior temporal sulcus (black arrow) can be appreciated between the normal case (B) and ACC case (D).

Fig 4.

In utero MR of a 30 week (A and B) normal fetus and (C and D) aged-matched ACC case from group 2. Sulcation delay is apparent between the normal and ACC case; the normal case demonstrates clear formation of the superior frontal sulcus (black arrowhead), inferior frontal sulcus (white arrow), and the superior temporal sulcus (black arrow), while these are not formed on the ACC case (expected location indicated).