ethmocephaly

description

ethmocephaly is the term used to describe a proboscis separating severely hypoteloric orbits, generally associated with marked microphthalmia and absent nasal structures. the nasal bones, maxilla, nasal septum and turbinates are missing, the lacrimal and palatine bones united. ears are usually lowset and malformed. ethmocephaly is morphologically closely related to cyclopia, and both malformations predict alobar holoprosencephaly. as in cyclopia, there is a predilection for affected females. ethmocephaly is the least common facial subtype in a spectrum of ocular and facial malformations which result from the abnormality in the development of the forebrain and frontonasal process which leads to holoprosencephaly. the eyes, orbits, and most of the midfacial structures may be absent; the eyes and orbits may be normally formed but closely set, with a single nostril, or the facial malformation may fit into the spectrum between these extremes. the correlation between face and brain in holoprosencephaly suggests an intimate relationship between the developing prosencephalon and the neural crest cells which give rise to the frontonasal process. variation in severity may occur because of differences in magnitude, timing or susceptibility. less frequently, a proboscis is not associated with ethmocephaly and holoprosencephaly. a lateral proboscis is offset from the midline and represents incomplete formation of one side of the nose. the individual is usually otherwise normal, although there may be an associated cleft palate. when both nostrils are normally formed, an additional proboscis may occur secondary to the presence of an accessory olfactory placode. rarely, the proboscis is located lateral to the outer canthus.