Sonography of fetal agenesis of the corpus callosum: a survey of 35 cases.

Agenesis of the corpus callosum was identified by ultrasound examination in 35 fetuses between 19 and 37 weeks' gestation. The ultrasound findings included absence of the corpus callosum and cavum septum pellucidum (hypoplasia in one case of partial agenesis of the corpus callosum), a typical 'teardrop' configuration of the lateral ventricles, distension of the interhemispheric fissure, upward displacement of the third ventricle, radiate arrangement of the medial cerebral gyri, and abnormal branching of the anterior cerebral artery. Associated anomalies were identified in 20 fetuses, including heterogeneous malformations and chromosomal aberrations (mosaic-trisomy 8 in three, trisomy 18 in two and partial duplication 8p in one). Five cases of agenesis of the corpus callosum were identified in a population of pregnant patients prospectively investigated because of genetic risk for agenesis of the corpus callosum or related syndromes. In this group, no diagnostic errors were made. Long-term neurological follow-up (6 months to 11 years) was available in 11 infants with antenatal diagnosis of isolated agenesis of the corpus callosum. Normal intellectual development was present in nine, and a low intellect (developmental quotient between 70 and 85) was found in two. It is concluded that fetal agencies of the corpus callosum is associated with elusive sonographic findings that can, however, be accurately identified by targeted examinations. In routine sonograms, an increased atrial width and/or failure to visualize the cavum septum pellucidum should arise the suspicion of fetal agencies of the corpus callosum. Given the high frequency of associated anomalies, prenatal diagnosis of agencies of the corpus callosum dictates the need for a careful survey of fetal anatomy and karyotyping. The prognosis is isolated agencies of the corpus callosum remains uncertain, although it is expected that a normal or boarderline intellectual development will occur in many cases. Copyright 1993 International Society of Ultrasound in Obstetrics and Gynecology