Use of Amplification in Children With Unilateral Hearing Loss

Unilateral hearing loss (UHL) is defined as decreased hearing in one ear, with normal hearing
thresholds in the contralateral ear. Approximately 0.83/1000 newborn children are found to
have UHL. It is estimated that about 3-5% of all children in the United States are eventually
diagnosed with UHL. When the cutoff for normal hearing is placed at 15 decibels (dB), this
incidence is as high as 6.3%, which corresponds to a prevalence of 6.2 million children
nationally. The management of UHL continues to be an area of debate, as the handicap
associated with UHL is often underestimated. In fact, those with UHL often go without
assistance due to lack of recognition of the disability by some health and educational
professionals, who have claimed that this hearing loss "attracts little attention from either
patient or parent" and that "these children experience few communicational or educational
problems." However, in evaluation of children with permanent hearing loss, rates of children
who need speech/language intervention and aural rehabilitation are not significantly
different between those with bilateral permanent hearing loss and those with unilateral
permanent hearing loss. Unfortunately, children with UHL are half as likely to be referred
for hearing testing as those with bilateral hearing loss.

Studies have demonstrated the negative impact of unilateral hearing impairment in children.
Educational and behavioral difficulties have been clearly shown, with a number of studies
demonstrating increased rates of failure of at least one grade in children with UHL when
compared to their classmates with normal hearing (24-35% vs. 3.5%). Additionally, increase in
special educational needs (12-41%) and frequent problems with behavior have also been noted
in this population. In several studies, Lieu and colleagues have shown poorer performance for
children with UHL. In a study looking at oral and written language scores, children with UHL
did significantly worse than their siblings, who served as matched controls, on language
comprehension, oral expression, and oral composite scores. In addition, these children were
four times more likely to have Individualized Education Plans (IEPs) and twice as likely to
have received speech-language therapy.

Despite these findings regarding the impact of UHL on children, there is a paucity of
literature to support or refute the efficacy of hearing aid use in improving measurable
academic, behavioral, or quality-of-life (QOL) outcomes. While hearing related
disease-specific quality of life measures for children were not developed until very
recently, previous studies in adults with UHL reported decreased quality of life, with
increased frustration and shame due to hearing disability. The Hearing Environments and
Reflection on Quality of Life questionnaire, or HEAR-QL, an instrument developed and
validated at Washington University in St. Louis for young children with hearing loss
initially (2011) and then later for adolescents (2013), examined effects on environments,
activities, and feelings of children with both unilateral and bilateral hearing loss.
Significantly lower scores, indicating poorer quality of life, were seen in patients with
both UHL and bilateral hearing loss. Interestingly, differences in quality of life between
children with UHL and children with bilateral hearing loss were found to be significant in
only 1 out of 3 subdomains.

A 2010 study by Johnstone et al. demonstrated that children with UHL who used amplification
at a young age (6-9 years) had improvement in localization acuity, while those who received
amplification at an older age (10-14 years) noted impairment in localization. This may
indicate that the timing of initiation of amplification in UHL may play an important role in
whether the intervention is beneficial. In addition, Noh and Park's study in 2012
demonstrated that children with UHL needed to sit 3.5 meters closer to the teacher to obtain
the same speech discrimination scores as children with binaural hearing. While this can be
accomplished in a small room setting, this may not be possible at all times in all classes,
and it is certainly not translatable to hearing environments outside of the classroom. It is
not clear whether adding amplification to would eliminate this handicap and improve quality
of life, behavior, or academic performance.

Current interventions: Multiple options exist for management of UHL. Preferential seating in
the classroom is often the first line of treatment utilized, placing the child at the front
of the classroom with the better hearing ear toward the teacher. Evaluation of the classroom
by an educational audiologist or other specialist in the education of children with hearing
loss in order to optimize the listening environment is another commonly utilized modality for
managing UHL. Interventions such as carpeting, tennis balls placed on the legs of chairs, and
selection of a classroom with lower ambient noise levels from outside traffic or air handling
equipment can reduce significantly improve signal to noise ratios for the student. Another
modality for improving signal to noise ration is use of a frequency-modulated (FM) system in
the classroom, which specifically amplifies the teacher's voice via a microphone worn by the
teacher. This increases the signal-to-noise ratio for the teacher's voice as it does not
amplify background noise. Differentiating relevant sound signals from background noise a
particularly challenging problem for children with UHL. Other options for management of UHL
include various forms of amplification including a unilateral hearing aid, contralateral
routing of sound (CROS) systems, and potentially cochlear implantation (though this practice
has not been widely adopted in children with UHL in the United States).

In the only study to date comparing the above modalities to one another, Updike compared
speech perception measures in 6 children, ages 5 to 12 years, with mild to profound UHL with
use of FM systems, CROS aids, and conventional hearing aids. He concluded that FM systems
were beneficial in all hearing situations and in all degrees of hearing loss. In addition, he
stated that neither hearing aids nor CROS aids provided benefit in speech understanding, and
both may worsen speech perception in noisy situations. Multiple limitations exist with this
study, including a small sample size and lack of a time period for the patients to adjust to
the use of amplification.

In studies looking at acceptance of hearing aid use in children with UHL, children with mild
to moderately severe hearing loss tended to accept hearing aids, while those with severe to
profound hearing loss were less accepting. Parental satisfaction with hearing aids in this
population has been good, with many noticing improved hearing for their children. More
recently, Briggs et al. published a study looking at 8 children, ages 7 to 12 years, with
mild to moderately severe UHL, who were aided with digital hearing aids. Although speech
perception scores did not show significant improvement, parents subjectively reported
significant improvement in quality of life after 3 months of use. In one German study of 3
children with severe to profound unilateral hearing loss, improvement in speech understanding
in noise and sound localization following cochlear implantation was observed and subjective
improvement was reported by parents.

Compliance with use of amplification should also be considered in these cases, as Fitzpatrick
et al. demonstrated in a study of 670 children with unilateral or bilateral hearing loss.
While amplification was recommended in 90%, less than two-thirds of the children wore their
hearing aids consistently.

To date, only two studies exist which examine the use of amplification in children with
unilateral hearing loss. Both studies are limited by small sample size. In addition, the
earlier study evaluated analog hearing aids, whereas in the present day, digital hearing aids
are widely used, and was further limited by a very short study period. Our study proposes to
examine whether children with UHL note improved quality of life when using amplification via
a hearing aid in conjunction with conventional classroom accommodations including an FM
system.

In our study we will compare the use of conventional measures to conventional measures plus a
digital hearing aid on the affected ear using validated quality of life instruments
administered to the subject, the subject's teacher, and the subject's parent. The instruments
used will be the HEAR-QL, the CHILD, and the LIFE-R (See outcome measures for details).

Each of the surveys will be administered five times in total: at the time of enrollment, once
at the midpoint of the first treatment arm, once after completion of the first treatment arm,
once at the midpoint of the second treatment arm, and once after completion of the second
treatment arm. Comparisons will then be made among groups as described later in this
proposal.

Our practice is well suited to carrying out this study as we are a tertiary care center
serving a large region. Our multidisciplinary pediatric hearing loss clinic allows children
to be evaluated and longitudinally followed in conjunction with the audiology, speech and
language pathology, neuropsychology, and medical genetics. In the past year, there were over
300 visits coded for unilateral hearing loss based on ICD-9 codes, with 70 unique patients,
making recruitment of our target sample size over the 3-year study period feasible. The
potential impact of this study is great, as there is no consensus as to whether amplification
should be recommended for children with unilateral hearing loss, and a study of this power
would serve as a useful guide in this decision-making process.

Inclusion Criteria:

Children ages 6-12 years with mild to moderately severe unilateral hearing loss, with
thresholds across 4 frequencies ≥ 25 dB but < 70 dB in the worse hearing ear; Normal
hearing in the contralateral ear, defined as thresholds ≤ 20 dB from 250 Hz to 8000 Hz;
Unaided word recognition scores of ≥ 80% in worse hearing ear

Exclusion Criteria:

Contralateral hearing loss; Significant cognitive impairment; Middle ear disease that has
not been addressed; Inability to commit to treatment program