Agenesis of the corpus callosum: What to tell expecting parents?

Agenesis of the corpus callosum (ACC) is one of the most common brain malformations, with an incidence estimated to range from 0.5 to 70 in 10,000 among the general population. Prenatal diagnosis is made via ultrasound; however, fetal MRI is useful to confirm or exclude the presence of associated cerebral abnormalities-mostly cortical malformations-that may affect postnatal prognosis. When no additional central nervous system (CNS) or extra CNS anomalies are identified and no genetic cause is found, an isolated ACC is diagnosed. Overall, in cases of ACC, an underlying genetic cause can be identified in up to 12.5% with chromosomal microarray (CMA) and up to 47% with whole exome sequencing (WES). In cases where ACC is the only anomaly detected, the yield of WES is 30%. Postnatal outcomes are variable and depend on whether the condition is isolated or not. In truly isolated ACC, outcomes range from normal in 65% of cases through mild to severe neurodevelopmental impairments in 35% of cases. An interdisciplinary team of medical experts is key in guiding parents toward informed decision-making in pregnancies complicated by ACC. Considering current and expected advancements in genetic testing and imaging technologies in upcoming years, we herein summarize current recommendations for the management and prenatal counseling of expecting parents of fetuses with ACC. Our review pertains primarily to expecting parents of fetuses with complete ACC. What is already known about this topic?Agenesis of the corpus callosum (ACC) is among the most common fetal brain malformations, with a variety of postnatal neurodevelopment outcomes.Diagnosis of ACC relies heavily upon fetal ultrasound and neurosonography. MRI is a valuable adjunct to assess additional central nervous system anomalies.Genetic testing is key with whole exome sequencing demonstrating a yield of up to 47% for all cases of ACC.A multidisciplinary team can provide the best pre- and postnatal counseling for expecting parents.What does this review add?We outline the current prenatal diagnosis and management of ACC.We summarize the most important aspects of ACC that should be discussed with expecting parents.