Agenesis of the corpus callosum: What to tell expecting parents?
1Michael G. DeGroote School of Medicine, Waterloo Regional Campus, McMaster University, Hamilton, Ontario, Canada.
Insights
Agenesis of the corpus callosum (ACC) is a common brain malformation. Genetic testing and imaging advancements aid in diagnosing ACC and predicting postnatal outcomes for affected infants.
Area of Science:
- Neuroscience
- Medical Genetics
- Prenatal Diagnosis
Background:
- Agenesis of the corpus callosum (ACC) is a frequent congenital brain malformation.
- Prenatal diagnosis relies on ultrasound, with fetal MRI crucial for identifying associated anomalies impacting prognosis.
- Isolated ACC diagnosis occurs when no other central nervous system (CNS) or extra-CNS abnormalities are found, and no genetic cause is identified.
Purpose of the Study:
- To review current recommendations for managing and counseling parents regarding fetuses diagnosed with complete ACC.
- To highlight the role of advanced genetic testing and imaging in prenatal diagnosis and prognosis.
- To provide guidance for interdisciplinary teams managing pregnancies complicated by ACC.
Main Methods:
- Literature review of current diagnostic and management strategies for ACC.
- Analysis of genetic testing yields (CMA, WES) in identifying causes of ACC.
- Evaluation of postnatal outcomes based on isolated versus non-isolated ACC.
Main Results:
- Genetic causes for ACC are identified in up to 47% of cases with Whole Exome Sequencing (WES).
- For isolated ACC, WES yields a genetic cause in 30% of cases.
- In truly isolated ACC, 65% of individuals have normal outcomes, while 35% experience neurodevelopmental impairments.
Conclusions:
- Accurate diagnosis and prognosis of ACC rely on advanced imaging and genetic testing.
- Interdisciplinary team management is essential for informed parental decision-making.
- Understanding genetic contributions and outcome variability is critical for prenatal counseling in ACC cases.
Abstract:
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.
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