Fetal corpus callosal anomalies: from disease of classification to classification of disease

Abstract

Figure 2 A wide range of corpus callosal (CC) abnormalities, some of which are of questionable clinical significance, have been described in the fetus.(a) Normal appearance of the CC in the midsagittal view of the fetal head, displayed using a transvaginal neurosonographic approach.Note the four components of the CC (R, rostrum; G, genu; B, body; S, splenium).(b) Complete agenesis, with none of the four components visible.(c) Partial agenesis in the second trimester.The genu and the splenium cannot be seen and the cavum septi pellucidi (CSP) is very small.(d) Partial agenesis in the third trimester.In this case, a highly abnormal CC is present (arrows), with a linear, streak-like appearance.(e) 'Thick CC', in which the genu and the anterior part of the body (arrowheads) are significantly thicker than the rest of the CC.(f) Hypoplastic CC.The CC is thin, but in this case it is not clear whether this is due to compression from the wide CSP below or whether the CC is truly hypoplastic.(g) 'Short CC' (arrows); this highly questionable definition has been challenged by several researchers (see text).(h) Dysraphic CC (arrows), with poor visualization of the rostrum and genu (arrowhead).In this case, etiology was fetal cytomegalovirus infection.(i) Clastic lesion of a previously normal CC (arrowheads), destroyed by acute hypoxia due to death of the co-twin in a monochorionic monoamniotic pregnancy.

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