Page 19 - Characterization of genetic neurodevelopmental disorders at adult age, with a focus on 22q11.2 deletion syndrome - Emma Boersma

General introduction
integrated with input from other sensory systems to guide behavior and
movement.50 Sensory systems play an important role in communication,
building and maintaining social interactions, and signaling of danger.
Deficits may result in accidents, including falling, and may cause or
aggravate symptoms of anxiety and depression.51, 52
Individuals with an intellectual disability, as a group, were reported to have
an increased risk of hearing and/or vision loss at an earlier age compared
to individuals from the general population.53 Knowledge of sensory (dys)
function in GNDs, except for Down syndrome,11, 54-56 is however limited.
The following paragraphs give a general introduction to the auditory
and ophthalmic system and to what is known so far in individuals with
22q11.2DS.
Hearing and otologic findings
Hearing can be tested with audiometry, which makes it possible to
differentiate between types of hearing loss and to describe the configuration
of hearing thresholds in terms of severity and frequencies (tones) that are
affected.57 Hearing loss can be conductive, resulting from problems in the
middle and/or external ear, sensorineural, resulting from cochlear damage,
or mixed.58 Conductive hearing loss may be caused by, for example, ear wax
or fluid in the middle ear, and sensorineural hearing loss may be caused by
noise damage, medication or aging.58 Depending on the severity and type of
hearing loss, hearing aids can be prescribed.58
In a large sample of adults with an intellectual disability hearing loss was
found in about 35%, which is higher compared to the general population.59
The global estimate of hearing loss is 20% in the general population and
increases with age, most notably after the age of 50 years.60 Age-related
hearing loss in the general population affects 40% of individuals aged 65
years and older.61 It starts with a high-tone loss, which has an adverse effect
on hearing sensitivity and speech understanding with background noise,
and in a more advanced state, on localization of sounds.61, 62
In 22q11.2DS, there have been several studies examining hearing and
otologic problems in children, with only a few that included adults.35, 63-66
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