Corpus Callosum

Agenesis of the corpus callosum (ACC) is a congenital birth defect characterized by an absence of a corpus callosum. This condition can occur in isolation (with little to no impact on cognitive performance) or can occur as part of abnormalities such as Dandy-Walker syndrome, Arnold-Chiari malformation, schizencephaly, holoprosencephaly, Andermann syndrome, or Aicardi syndrome (a syndrome more commonly seen in females). Midline facial defects often accompany ACC.

COLOR IMAGING OF THE CORPUS CALLOSUM BY DIFFUSION TENSOR IMAGING

A-C diffusion weighted imaging (DWI) measures the rate of water diffusion in brain tissue, measured using an apparent diffusion constant (ADC). Diffusion tensor imaging (DTI) is used to measure the “anisotropy” or randomness of water diffusion. The degree of anisotropy is called fractional anisotropy (FA), and is measured from 0 to 1, where 0 is unrestricted and 1 is fully restricted and diffuses along only one axis. Due to the properties of white matter, parallel bundles of axons and the myelin sheaths allow for a certain orientation of water diffusion. Water diffuses more rapidly along the direction of aligned direction, and more slowly perpendicular to this direction. This enables “visualization” of white matter tracts based on the calculated FA values. To discriminate the direction of different fiber bundles, a color scheme is adopted in which green represents an anterior-posterior direction, red a left-right direction, and blue a superior-inferior direction. In these images of the corpus callosum, components of this major commissural bundle are represented in red.

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