How does the corpus callosum develop, and why is this important?
The corpus callosum develops front to back except for the rostrum (anterior genu, body, splenium, and rostrum last). This is important because an in utero insult may result in destruction of part of the corpus callosum. If posterior portions of the corpus callosum are present and anterior portions are not, this means that they were present at one point and were destroyed. If posterior portions are absent instead, this may mean that they did not develop.
Which entity does not follow the normal rule of corpus callosum development?
Holoprosencephaly, previously described, may follow an atypical pattern of corpus callosum development, in which the posterior portions develop and the anterior portions do not. This is termed atypical callosal dysgenesis.