See also: Congenital hearing loss
Timothy C. Hain, MD of Chicago Dizziness and Hearing.
Last updated: September 5, 2017
|MRI read by radiologist as showing hypoplastic lateral canals. Patient with Down's syndrome.||Normal MRI of inner ear for comparison purposes.|
There is a small literature regarding inner ear malformations in persons with Down's syndrome (Trisomy 21).
Nightengale and associates (2017) reported that "Permanent hearing loss was identified in 24.9% of the children, among whom bilateral (75.4%) and conductive (33.3%) hearing losses occurred most often. Of children with DS, 22%-30% experienced a transient hearing loss, with a high incidence of middle ear pathologies from infancy until early adulthood. Twenty-three percent were current hearing aid users or had them recommended in a treatment plan. " The average age was about 6 years old, so this is a very high prevalence of hearing deficits.
Middle and external ear abnormalities, such as stenosis of the external canal, poor mastoid pneumatization, middle and mastoid opacification, and cholesteatoma are commonly described. There is also a high incidence of inner ear abnormalties. Blaser et al (2006) noted that vestibular malformations and a small bony island of the lateral semicircular canal (< 3mm) is typical. Some patients also exhibit fusion of the lateral canal into the vestibule, enlargement of the vestibular aqueduct and endolymphatic sac fossa enlargement, cochlear nerve canal hypoplasia, and stenosis or duplication of the IAC.
Igarashi and Takahashi reported that the cochlea was shorter in temporal bones in 4 persons with Down's syndrome (1977). Harada and Sando (1981), in 12 subjects, noted that there were numerous middle ear abnormalities, and a shortened cochlea, most of the vestibular measurements were normal. Bilgen et al (1996) found that in 6 temporal bones, 6 had a "short" cochlea, and 4 had Mondini's cochlea.
Overall, these radiological findings suggest that persons with Down's syrome would be likely to have intralabyrinthine pressure disorders, such as are found in the enlarged vestibular aqueduct syndrome, as well as perilymph fistulae.