Agenesis is a result of an insult occurring at approximately 8-12 weeks gestation 2,4 resulting in failure to form the corpus callosum. The white matter tracts which usually cross the midline, instead are oriented vertically, separating the lateral ventricles widely, in a racing car sign configuration.

Agenesis of the corpus callosum, a brain defect present at birth, can be mild or severe. It’s usually not fatal, and specific therapies can help. Although the disorder is generally diagnosed in the first two years of life, some cases are diagnosed later.