Thick corpus callosum in the second trimester can be transient and is of uncertain significance

Depiction of a thick corpus callosum (CC) in utero is rare, and is generally associated with severe brain anomalies. Our aim was to describe a group of fetuses diagnosed during second-trimester ultrasound examination as having an apparently isolated thick CC, which normalized subsequently in the cases followed to term.

Among 59 fetuses referred to the Ob-Gyn Ultrasound Division of Lis Maternity Hospital with suspected callosal anomalies between January 2013 and June 2014, we identified nine cases with an apparently isolated thick CC for inclusion in this retrospective cohort study. Length and body thickness of the CC were compared with previously published nomograms. Fetuses with a suspected isolated thick CC were identified and followed until delivery or termination of pregnancy (TOP). Evaluation consisted of chromosomal analysis, at least one magnetic resonance imaging (MRI) examination and repeat ultrasound examinations. Postnatal evaluation included brain ultrasound examination, MRI when indicated and neurodevelopmental assessment through validated pediatric questionnaires.

The nine fetuses were diagnosed with an apparently isolated thick CC at a mean gestational age of 23 + 5 (range, 21-29) weeks. Eight exhibited a CC body thickness ≥ 2SD above the mean for gestational age and one exhibited only a thickened genu. Six also exhibited a relatively short CC. Two patients opted for TOP but declined autopsy. In five of the seven remaining fetuses, the CC thickness normalized during follow-up. In the remaining two, the increased CC thickness was a variant of the cingulate sulcus. The CC length remained ≤ 2SD in five of the six fetuses with a short CC. Fetal MRI was performed and confirmed the diagnosis in six fetuses. The karyotype was normal in all fetuses. Short-term neurodevelopmental outcome was reported as normal in all six children with complete follow-up.

Although the number of fetuses in our study is relatively small, it seems that an apparently isolated thick CC is not necessarily associated with poor prognosis. In such cases, a definitive diagnosis should not be reached based on a single measurement and repeat follow-up examinations during the third trimester are recommended. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.