NeurometPlus

Incidence

The incidence of ACC is estimated to be 0.7-5.3% of live births and has been observed to be more common in males. Most children are diagnosed at birth and there is no known racial preference. ACC is caused by a yet unidentified gene alteration in brain development. The inheritance pattern is highly variable and can be sporadic, X-linked (only boys are affected), autosomal dominant and autosomal recessive.

Clinical Characteristics

Agenesis of the corpus callosum (ACC) is a rare anomaly of brain development that results in the partial or complete absence of a structure in the brain known as the corpus callosum. The corpus callosum is a group of fibers that serve as the bridge between the two sides of the brain. ACC is not a specific disease or syndrome itself, but rather is a description of a finding that can be seen in many syndromes. It is present at birth and is occasionally associated with other anomalies of the central nervous system. ACC is often detected by routine prenatal ultrasound after the 6th month of pregnancy. After birth, children with ACC may present with seizures, an enlarged head due to accumulation of pressure in the brain (hydrocephalus), or delays in normal development mimicking cerebral palsy. Other findings that may be associated with ACC include: cysts in the brain, abnormalities in the shape of the brain surface, and encephalocele (herniation of brain tissue outside of the skull). These findings are often part of the Chiari II malformation. ACC is caused by a yet unidentified gene alteration in brain development. The inheritance pattern is highly variable and can be sporadic, X-linked (only boys are affected), autosomal dominant (only one defective gene required for disease), and autosomal recessive (must inherit two defective genes, one from each parent). There are several syndromes associated with ACC. Some of the more common chromosomal abnormalities are trisomy 13 (3 copies of chromosome 13) and trisomy 18. The more common metabolic disorders include glutaric aciduria type 2 and Zellweger syndrome. Other genetic syndromes are Aicardi, and hydrocephalus with stenosis of the aqueduct of Sylvius. The prognosis for children with agenesis of the corpus callosum is highly variable and is usually defined by the severity of other associated anomalies. In isolated, asymptomatic partial ACC, children have normal life spans.

Precipitants

None

Provocation Tests

None

Diagnostic Procedures

CT or brain MRI detect the abnormality. ACC is often detected by routine prenatal ultrasound after the 6th month of pregnancy.