Malformations and anomalies of the ear

Congenital deafness usually involves either the sound conducting system or the neurosensory apparatus of the internal ear. It rarely involves both systems. This kind of abnormality is generally inherited. It may also be caused by rubella virus infection during week 7 and 8 of development. Abnormalities in the conduction of sound also occur in mandibulofacial dysostosis (Treacher Collins syndrome).
Otosclerosis is an autosomally dominant inherited disorder in which the footplate of the stapes becomes fixed at the fenestra vestibuli by fibrous or ossified tissue. As a result, sound conduction is impaired and loss of hearing is progressive.
The external ear exhibits different forms of abnormalities, which range from the auricles being too large (macrotia) or too small (microtia). The auricles may also fail to develop at all (anotia).