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Medical Image Database, Atlas, and Teaching File
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The corpus callosum forms during the last half of the first trimester and first half of the second trimester. Agenesis of the corpus callosum or dysgenesis can have varying degrees of severity. Abscence of the cingulate gyrus, gyri radiating to the lateral ventricle, colpocephaly (dilated occipital horns of the lateral ventricle), and a parallel configuration of the ventricles are all findings in dysgenesis of the corpus callosum.

A lipoma can be associated with agenesis or dysgenesis of the corpus callosum. It should not be removed since normal fibers and vessels traverse through this lipoma. The bright signal on T1 limits the most likely items on the differential to fat, blood, protein and contrast. The chemical shift artifact (which occurs in the frequency encoding direction) is best identified on the proton density and T2 weighted images. This is seen as the black line on the anterior aspect of the mass with "shift" of signal posteriorly to the posterior portion of the mass (lipoma).