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.