ANATOMICAL ABNORMALITIES IN MANDIBULOFACIAL DYSOSTOSIS

A detailed dissection of the head and neck of a 7-month-old boy with mandibulofacial dysostosis is described and compared with other reported cases. A general growth retardation was found in the bones of the basicranium and calvaria as well as the face. The base of the skull was kyphotic, and the elements derived from the branchial arches articulated with the basicranium more anteriorly than usual. Certain middle ear structures were found to be extracranial. The facial muscles were generally normal except for the absence of elevators of the upper lip. The laryngeal cartilages were shortened anteroposteriorly, resulting in drastic reduction of the rima glottidis. The attachments of the masticatory muscles to the mandible suggested that the area of the temporomandibular joint had not completed normal differentiation, and that that part of the mandible which functioned as a condyle was actually an ossification around Meckel's cartilage. There was no infarorbital foramen, and the infraorbital neurovascular bundle was distributed instead to the palate. Clinical and functional correlations of the various defects are considered. Theories of pathogenesis are discussed on the basis of these findings. It is argued that these observations could be accounted for by an altered intercellular matrix with separate effects on skeletal growth and neural crest cell migration.