Page 144 - Characterization of genetic neurodevelopmental disorders at adult age, with a focus on 22q11.2 deletion syndrome - Emma Boersma

Chapter 4
Hearing loss
The proportion of adults with hearing loss (78.3%) was much higher
in comparison to two previous studies in adults with 22q11.2DS that
reported hearing loss in 28.5% and 40.9%, respectively.3, 8 However, when
interpreting the findings, it is important to take into account the study
designs, definitions for hearing loss, and age and size of the samples in
the different studies. The first study was a retrospective chart review in 78
adults at a mean age of 31.5±10.5 years, and included those with hearing
loss reported in the medical records.3 No audiological assessments were
performed. The proportion of adults with a documented history of hearing
loss was similar to this study (28.5% versus 31.7%). In the second study,
22 of 24 adults underwent an audiological assessment at a mean age of
25 (range 19-38) years.8 The same definition for hearing loss was used as
in this study. However, in the current study hearing was measured up to
8, instead of 6 kHz. Also, sensorineural hearing loss was found in 33.3%
(n=3) of those with hearing loss, comparable to findings in the current study
(35.9%). Unilateral conductive hearing loss was found in a much higher
proportion of the participants (44.4% versus 12.8%) compared to this study.
However, absolute numbers were low affecting reliability of those findings,
and results were possibly influenced by a few younger participants.8
Another study, reporting on hearing in 40 children and adults at a mean age
of 15 years (range 6 -36 years), who received audiological testing as part
of the research study, found 60% of participants to have hearing loss in at
least one ear, defined as >20 dB HL from 0.5-1-2 kHz.16 Conductive hearing
loss was the most common type (54%), sensorineural (4%) or mixed (2%)
were found less often.16 In line with results from our study, they did find high-
frequency hearing loss in the majority of individuals, which was assumed to
be of sensorineural origin.
Potential contributors to hearing loss in 22q11.2DS
There are several potential contributors to hearing loss in adults with
22q11DS.7, 17 First, chronic otitis media, with or without congenital inner ear
abnormalities,18 may result in the cochlea being more vulnerable in individuals
with 22q11.2DS compared to the general population.7, 16 Second, early
physiological degeneration and other medical conditions and their treatment,
may lead to hearing loss.19 Age-related disorders such as Parkinson’s disease
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