Clinical appearance of spontaneous and induced first and second branchial arch syndromes.

The clinical appearance was investigated of 29 patients with mandibulofacial dysostosis, 26 with hemifacial microsomia, and seven with thalidomide-induced malformations affecting derivatives of the first and second branchial arches. Malformations of the external ear, ear canal, middle ear, zygoma, maxilla, mandible, and lower eye lid were prominent features of the syndromes. Facial nerve and 6th cranial nerve paralysis as well as anophthalmia or microphthalmia were seen only in patients with hemifacial microsomia and in the thalidomide-induced syndrome. We compared the clinical results with those in an animal model in which an induced first and second branchial arch syndrome depends on disturbed migration of neural crest cell during early embryogenesis. The critical time for a similar process in humans would be between the 20th and 29th days of pregnancy.