Pathogenesis of dysplasias of the face and the ear and dystopias of the temporal region.

Dysplasias of the face and ear are supposed to be caused by a premature involution of 3 different embryonal arteries of the branchial arches: (1) Dysfunction of the mandibular artery causes the otocephalia syndrome; (2) that of the stapedial artery causes dysplasias of the face; (3) dysfunction of the hyoid artery entails dysplasias of the ear; and (4) combination of (2) and (3) (dysfunction of truncus hyostapedialis) results in simultaneous dysplasias of the face and the ear. The earlier the deficiency of blood supply occurs the more serious the resulting dysplasias are. The dystopias in the temporal region (auricles, facial nerve, ossicles, petrous bone) are the consequence of an overbending of the proximal hyoid arch caused by a retardation in the development (shortening) of the mandibular arch. Therefore, dystopias of the ear always occur together with dysplasias of the face. Phenotype and appearance on radiographs are discussed.