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HEARING IMPAIRMENT & DOWN'S SYNDROME
Susan Snashall (UK)
Introduction
Middle ear disease and inner ear hearing loss are both more common
in those with Down's syndrome than in the general population.
In combination with intellectual impairment even a slight hearing
loss can have a significant impact upon the acquisition of language.
People with intellectual impairment often have difficulty processing
speech, especially in noise, and in locating the source of a sound.
A mild hearing loss will make these tasks even more difficult.
People with Down's syndrome are unlikely to complain of hearing
impairment and it is necessary for hearing loss and middle ear
disease to be detected by screening procedures if remedial action
is not to be delayed.
Anatomy
Orofacial and craniofacial development associated with Down's
syndrome contribute to inner, middle and outer ear problems:
- the adenoids are large
- the nasopharynx is small
- swallowing is impaired
- the Eustachian tube itself is very narrow and more horizontal
than usual.
These factors reduce aeration of the middle ear, giving rise
to otitis media with infection.
- the outer ear canal is very narrow making it difficult to
visualise the eardrum and for the normal self cleaning mechanisms
to operate efficiently.
- wax is also more copious and more hard than usual, particularly
in adults.
- The outer ear is therefore often blocked by impacted wax.
- The hair cells of the cochlear may be missing, causing congenital
deafness, or simply prone to early degeneration.
Pathology
People with Down's syndrome produce copious mucus, which then
becomes infected due to immunodeficiency. Middle ear infections
are very common and may proceed to perforation and cholesteatoma.
Otitis media with effusion follows Eustachian tube dysfunction
and does not tend to resolve spontaneously because of the anatomical
characteristics. (In ordinary children 90% will resolve spontaneously
within 3 months).
Conductive hearing loss
This results from middle ear infections and from otitis media
with effusion (glue ear). It may be mild or moderate in degree,
but any degree of hearing loss will affect language development
in the presence of intellectual impairment. Adults will have conductive
deafness due to impacted wax, perforations or middle ear infections
and scarring.
Sensory-neural hearing loss
Children with Down's syndrome are more likely to have congenital
permanent inner ear hearing loss than the general population (which
has an incidence of 1:1000). From teenage years onwards they a
likely to develop degenerative cochlear changes, and most will
have a significant hearing loss by the age of 40 years.
Detecting hearing problems:
Children with Down's syndrome should have an annual hearing test
using a test suitable to their level of development:
- Newborns with Down's syndrome - objective test (Otoacoustic
emissions or auditory brainstem responses). Those who fail the
screen are then seen for further testing and intervention if
required. Behavioural observations will substantiate the objective
tests at this age
- Developmental age of 10 months - Visual Reinforcement
Audiometry.
- Developmental age of 2 years - Conditioning play audiometry
- Adults - Hearing assessment every 5 years using pure
tone audiometry if possible, supported by a word test.
Tympanometry, a technique for detecting fluid in the middle ear
space, is useful at all ages.
Detecting middle and outer ear disease:
All hearing tests should be accompanied by otoscopy as the ears
are so often blocked by wax and serious middle ear pathology will
be missed if not sought. Adults should have otoscopy every year
to detect wax.
Treating hearing impairment:
- Wax should be softened on a regular basis with olive oil and
removed by syringing as required.
- Antibiotics may control chronic infection of the nose, nasopharynx
and ears.
- Grommets/T tubes/Tympanostomy tubes, which are small tubes
placed in the ear drum to maintain air in the middle ear are
used if the external canal is large enough to give a surgical
view of the ear drum. They extrude spontaneously and may need
to be reinserted, as the otitis media is likely to recur.
- Surgical repair of perforations and removal of cholesteatoma
may be required
- Inner ear hearing loss can only be helped with amplification
using some form of hearing aid.
Hearing aids and Down's syndrome:
As hearing loss is likely to have such an impact upon language
development in Down's children, and upon cognition in Down's adults
suffering from early dementia, amplification is considered even
for mild hearing losses and for conductive hearing loss which
is likely to be present for more than a few months. The hearing
loss is almost always accompanied by recruitment, which can cause
sound intolerance. The hearing aid prescription will be such as
to avoid tolerance problems in noisy places such as special schools
and day centres. As the ears are small miniature ear level instruments
will be required. Hearing aids may only be worn for limited periods,
and if so this should be at times of language training. All children
will have the assistance of an Advisory Teacher for the Hearing
Impaired, and all adults the help of a Specialist Speech and language
Therapist.
Even with motivated carers personal hearing aids may not be tolerated.
For children a classroom FM system is an alternative as these
systems improve the detection of speech in classroom noise. For
adults the best solution may be a change in the communication
strategy used with the person.
This article first appeared on the site in 2002.
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