Cochlear Implantation in subjects with asymmetrical hearing loss

Background
Cochlear implantation has become a standard treatment for patients with
bilateral severe hearing to profound hearing loss. Rehabilitation with a CI is
designed for the deafened subjects unable to have a good speech perception on
both ears. A number of patients were seen recently who were in need for a
better rehabilitation, but who had one ear in which their hearing aid was just
sufficient to give them some speech performance. Their other ear functioned as
a deaf ear. This unique group of patients are in between sufficient and
insufficient hearing and because of their deaf ear they perform worse in noisy
environments. Their understanding of speech in noise is worse than in patients
with hearing aid use on both ears. These patients benefit from a CI in their
deaf ear for speech intelligibility in noise, localization and probably benefit
in music perception, but this was never well documented. Overall we believe
that their quality of life would improve subtantial. But up till now a study in
this asymmetrical hearing loss group has not been performed because of this
rare pathology and the focus on speech in quiet conditions instead of speech in
noise, localisation and quality of life.
The aim of this study is to observe the benefits obtained by adults that have
an asymmetrical cochlear hearing loss when wearing a CI in the worse ear and HA
in the contralateral ear. Changes in perceptual abilities, speech production,
localization abilities and music perception will be assessed over a 12 month
period of use of the CI with HA.

1.
To determine the benefit of a CI in the functionally deaf ear of patients with
asymmetrical hearing loss with moderate to severe hearing loss in their best
ear
in terms of speech performance (in quiet and noise) and localization

2.
To determine the benefit of a CI in the functionally deaf ear of patients with
asymmetrical hearing loss with moderate to severe hearing loss in their best ear
in terms of quality of life and music perception

Single center prospective non-randomised observational case-control study

Patients with an asymmetrical sensorineural hearing loss (SNHL) will be asked
to enroll in the study prior cochlear implantation. Their hearing and
questionnaires prior to implanation will be the baseline measurement. The
results of the objective and subjective measures in the following year will be
compared to these baseline results. A total of ten patients are planned to be
included in the study

All subjects will be fitted by the audiology department in the VUmc according
to the normal, clinical routine, similar to the care and follow-up of all
cochlear implant patients in VUmc. All CI and Hearing aid settings will be
optimized per subject. Testing shall be conducted pre implantation
(baseline/*control*) and at 3, 6, and 12 months post implantation. Additional
tests will be done objective testing (e.g. speech in noise) and questionnaires
shall be applied at those time points. Twelve months after start of the CI
rehabilitation is considered as endpoint.

All subjects will be fitted in the VUmc according to the normal, clinical
routine. All CI settings will be optimized per subject. Testing shall be
conducted pre implantation (baseline) and at 3, 6, and 12 months post
implantation. A test battery comprising both objective testing and
questionnaires shall be applied:

BURDEN
The number of TEST MOMENTS are EQUAL to the normal follow up moments.
The number of tests has slightly increases, with an EXTRA TIME CONSUME of 4
times 2-3 hours.
The participants also need to fill in 2 EXTRA QUESTIONNAIRES at different time
points

BENEFIT
The overall benefit for the patient and the group is to have a beter hearing.
Even when not participating in this study we expect their hearing to improve
with an CI.

RISKS
we expect no risks with the tests we use.

Speech tests: no risk
Localisation tests: no risk
Acoustical tests: no risk
Electrical tests:
Prevention is guaranteed for the two hazards that could possibly occur in this
study: 1) overstimulation causing patient
discomfort, and 2) build-up of electrical charge on electrodes or tissue due to
unbalanced stimulation.
ad 1) The overstimulation hazard is equal to this hazard in the normal CI
fitting software and is controlled by restricting the
performance of these measurements to clinical physicists experienced in CI
fitting.
2) The charge-unbalance hazard is prevented in the software provided by
Advanced Bionics.
Both risks are equal to all cochlear implant user during rehabilitation.

TESTS
Pure Tone Audiometry
* (Un)Aided situation: thresholds (dBHL) will be measured on frequencies 125 -
8000Hz
Speech recognition
* NVA, Bosmanlijsten at 65 dB SPL (3 lists)
Speech recognition in noise
* DIN-test (digits in noise test), overall level fixed at 65 dBA
- Speech and noise frontal
Spatial speech recognition in noise
* DIN-test (digits in noise test), overall level fixed at 65 dBA
- Speech left, noise right (plus and minus 900)
- Speech right, noise left
Localization
* Localization of everyday sounds (8 loudspeakers)
Questionnaires
* NCIQ
* IOI-CI
Music perception
* Music evaluation questionnaire (Mirza et al, 2003)