Hearing Problems in Down syndrome
Children use what they hear and see around them to learn about the world and how to communicate. Hearing impairment (including temporary deafness such as glue ear or wax impaction) that is not diagnosed or correctly managed can have a very negative effect on a child’s language and social development. Even mild hearing impairment in a child with Down syndrome can severely compromise speech development. Hearing impairment occurs in approximately 89% of children with Down syndrome.
Types of hearing Loss (deafness)
Anatomy of the ear
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Conductive Hearing Loss (CHL)
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Conductive hearing loss (CHL) occurs in approximately 70% of children with Down syndrome and is caused when sound cannot pass efficiently through the outer and middle ear to the cochlea and auditory nerve. Some children may have a very narrow or an hour-glass shaped ear canal. CHL can be because of glue ear (fluid in the middle ear) or a blockage of wax in the ear canal. Most CHL is temporary.
Sensory Neural hearing loss (SNHL) occurs in approximately 10 - 15% of children with Down syndrome and is caused by a fault in the inner ear or auditory nerve. This is the nerve that carries the sound signals to the brain. Most sensor-neural deafness is caused by a problem in the cochlea (the part that looks like a snail-shell of the inner ear which changes sound vibrations into electrical signals that are carried to the brain- see above No 3). This is usually because the hair cells in the cochlea are not working properly or the auditory nerve (the nerve that carries the electrical signals from the cochlea to the brain) is not fdunctioning correctly. SNHL is permanent. A small number of children are born with this type of deafness.
Mixed Hearing Loss (MHL) is a combination of sensory-neural hearing loss and Conductive hearing loss.