Agenesis of the Corpus Callosum
The Common Vein Copyright 2010
Definition
Agenesis of the corpus callosum is the congenital absence of the corpus callosum caused by lack of development. The term “isolated” means that an abnormality is not associated with other abnormalities. The isolated agenesis of the corpus callosum may not be manifested by symptoms, but can be associated with intellectual deficit (manifested most often by difficulties in school), seizures or behavioral disorders.
Normally, the corpus callosum begins to form during the third month of pregnancy and is completely formed at the end of the 5th month. The degree of agenesis of the corpus callosum depends on when the development of the corpus callosum stops. It is unclear precisely what affects this development, but some cases, inflammation, infection contracted by the mother during pregnancy (eg rubella), a chromosome abnormality, a metabolic disease or intoxication (by alcohol or drugs such as cocaine) may be involved.
The agenesis of the corpus callosum may be associated with other malformations, brain or other; causes can be several. The exact prevalence is not known, since frequently it is assymptomatic. It is present in 1: 300 to 1:4000 according to some studies.
Symptoms depend on the severity of the agenesis, and the brain’s ability to compensate the anomaly by circulating information and integrating it differently; this is what probably explains why some people have no symptoms.
It is thus frequently discovered by chance during the workup from another illness or trauma.
Infants with agenesis of the corpus callosum can be hypotonic, which is often the first symptom. Delays in acquiring the sitting, standing and walking may result from this hypotonia. In early school years, children may appear to show learning difficulties: in 20 to 25% of cases, children have a moderate to severe mental retardation. In 75% of cases, their IQ is normal or slightly below average. Fi nally, some children have behavioral problems, such as deficit of attention or hyperactivity.
Radiologically, callosal agenesis can be detected by transfontanellar ultrasound in newborns. A CT scan or MRI may also help accurately make the diagnosis in children and adults. It is common that the malformation is detected before birth, during the 2nd and 3rd trimester ultrasound of pregnancy. A fetal MRI may provide diagnostic certainty in case of doubt.
There is no treatment for this condition, since it is due to a malformation.