Cerebello-cortical heterotopia in dentate nucleus, and other microdysgeneses in trisomy D1 (Patau) syndrome.

Several new histological findings in six cases of the trisomy D1 syndrome are described: hyperplasia of fetal structures (indusium griseum, median raphe of the medulla oblongata) and completely developed cerebellar cortical heterotopia in the dentate nucleus. In one case, a heterotopic pontine nucleus was found within the cerebellar white matter. The coexistence of overdeveloped and remaining fetal structures is emphasized. Several hypotheses regarding cerebellar dysgenesis are discussed.