Dorsal cyst malformations. Part I. Clinical study and critical review on the definition of holoprosencephaly.

Among the cerebral malformations accompanying cystic cavity in the dorsal midline, common radiological findings of galenic dysgenesis are found in 10 cases, which are now reported as dorsal cyst malformations. The authors classified dorsal cyst malformations into prosencephalic, interhemispheric, and porencephalic types according to clinical, radiological, and presumed pathogenetic characteristics. In contrast to recent trends that most of cerebral malformations with dorsal midline dysgenesis are included in the holoprosencephalic category, the authors emphasize that these interhemispheric and porencephalic types of dorsal cyst malformations, though presenting interhemispheric cyst with callosal defect or broad communication between the lateral ventricles, should be separated from holoprosencephaly, because they are completely hemispheric.