Pseudoaprosencephaly: Aplasia of the Forebrain in a Median Facial Cleft Syndrome with Arhinia and Anophthalmia

Report of a female fetus aborted at the 25th week of gestation, with severe microcephalus, trigonocephaly, median cleft lip and palate, arhinia, and anophthalmia. On opening of the skull the cranial cavity seemed to be occupied only by hindbrain structures. The forebrain, including the tentorium cerebelli and the falx were absent. However, in the light microscope membraneous remnants of a collapsed forebrain vesicle were found. They were connected with the mid-brain brain and appeared as glio-mesenchymal membranes with an ependymal out-line at their inner surface. There was no cranioschisis. The formal relationship of this forebrain malformation to abobar dorsal sac holoprosencephaly, and its separation from hydranencephaly are discussed. In view of the gross absence of the telencephalon and the microscopic demonstration of remnants of a prosencephalic vesicle it is suggested to term this "missing link" in the classification of human CNS malformations pseudoaprosencephaly.