Handbook of Genetic Counseling/Hypoplasia - Agenesis of the Corpus Callosum

Hypoplasia - Agenesis of the Corpus Callosum Definition underdevelopment (hypoplasia) complete absence (agenesis) of the CC Corpus collosum The area of the brain (large fiber tract) which permits the exchange of information between the left and right cerebral hemispheres. "the seat of the soul". Used to be that the thickness of its body was related to the level of intelligence. Function is uncertain because there is no consistent pattern when it is malformed or absent. Embryology: forms between 9-16 weeks of development. anterior to posterior. Incidence rare; no specific numbers Diagnosis ACC is usually diagnosed between 0-2 years (by MRI or CT scan) but may never be dx. May occur as severe syndrome, a milder condition, or an asymptomatic finding Signs and Symptoms: Seizures (infantile spasms) Feeding problems Delays in holding head erect, sitting, standing and walking microcephaly Possible clinical impairments Deficit or delay in mental and physical development, hand-eye coordination and/or visual and auditory memory Could also include: hydrocephaly, seizures, dyskinesia, repetitive speech, headaches Etiology Most are isolated/sporadic Males and females equally affected May be caused by a genetic syndrome such as: Aicardi's syndrome: ACC, infantile spasms, severe mental retardation and chorioretinal lacunae Grubben syndrome Wolf-Hirschhorn syndrome: chromosome abnormality Opitz-Frias syndrome Joubert syndrome X-linked syndromes: Bertini, Opitz-Kaveggia, Orofaciodigital, Proud, Pyruvatedehydrogenase May be associated with other cerebral anomalies such as Arnold-Chiari malformation, Dandy-Walker syndrome, Andermann syndrome, schizencephaly, holoprosencephaly and migrational anomalies Sometimes associated with complex multi-system anomalies and chromosomal abnormalities (trisomy 13 and 18). Management No specific treatment. May involve managing treatment of other conditions such as hydrocephaly and seizures if they occur Prognosis Excellent in most isolated cases Does not cause death in vast majority Many will lead normal lives and have average intelligence Children w/ ACC and DD and/ or seizures should be screened for metabolic disorders. Mental retardation is not progressive Resources NINDS Agenesis of the Corpus Callosum Information Page www.ninds.nih.gov/health_and _medical/disorders/agenesis_doc.htm Agenesis of the Corpus Collosum. Mental Retardation and Congenital Malformations of the Central Nervous System. Warkany, J, Lemire, R, Cohen, M. Human Embryology. Larsen, WJ. Notes The information in this outline was last updated in April 2003.