Holoprosencephaly and related midline cerebral anomalies: a review.

We propose a simple pathogenetic mechanism that reduces a bewildering variety of central nervous system malformations to a manageable group sharing defects of midline prosencephalic growth. It is neither new nor innovative, but attempts to summarize many pathologic entities within a concept that accounts for known embryologic events and the sequence and timing of those events. We propose midline prosencephalic dysgenesis as a category of malformations including aprosencephaly, holoprosencephaly, septo-optic dysplasia, and agenesis of the corpus callosum.