An anatomic comparison of cebocephaly and ethmocephaly.

Cebocephaly (hypotelorism, single-nostril nose) and ethmocephaly (hypotelorism, interorbital proboscis) lie in the middle of the spectrum of craniofacial changes associated with holoprosencephaly. Because these defects and thorough anatomic studies of them are rare, knowledge concerning morphologic as well as pathogenetic relationships is lacking. We report the autopsy findings and anatomic features of the dried skull of a 31 week fetus with cebocephaly and the craniofacial dissection of a 36 week fetus with ethmocephaly. Both manifested dysplastic changes of the ethmoid bone and anterior portion of the sphenoid bone, with concomitant hypotelorism and defects of the medial orbital walls. Through these latter defects, the eyes were joined in the ethmocephalic fetus (synophthalmia). Other changes of bone (single optic foramen, approximated maxillae, choanal atresia, thickened palate) and soft tissue (eccentric or fused extraocular muscles, single optic nerve) in both fetuses resembled those reported in other cases of cebocephaly and ethmocephaly, as well as cyclopia. In the 19th century, both cebocephaly and ethmocephaly were classified as two-orbit variants of cyclopia, a view supported by the present study.