ELEctric Place-pitched Hearing Achieves Natural Tonotopy

In search of the best possible outcome for the severe hearing impaired who have
regained the ability to hear by means of a cochlear implant (CI), electrical
stimulation and the information it carries should match as closely as possible
to what the human brain naturally has evolved to cope with and learned to
process instead of relying on plasticity to adapt to an induced mismatch. At
the moment, however, CI*s are fitted with a *one size fits all* principle. This
is known to cause a mismatch between the frequencies presented by the CI
electrode array and the frequencies represented at the corresponding natural
acoustic location in an individual cochlea.

In this study it is hypothesized that an individual imaged based fitting that
pursues natural hearing alignment and is implemented from the start of the
rehabilitation process, will improve the individual outcomes of electric
hearing. The natural fitting strategy is thought to give rise to a steeper
learning curve, result in a better performance in challenging listening
situations, improve sound quality, complement better with residual acoustic
hearing in the contralateral ear and win the preference of CI-recipients.

CALF addendum:

Interim analysis of the ELEPHANT results revealed clear interindividual
differences with respect to the outcomes with and the preference for either the
natural or the standard frequency alignment. First results indicate that
patient-related factors determine FAT preference. We hypothesize that
differences in neural health of the stimulated area in the cochlea lie at the
basis of this preference. In order to evaluate this hypothesis, we want to
reinvite those patients that are willing to participate in order to perform a
number of additional measurements. This follow-up study is named CALF, acronym
for Cochlear health Allocation by Loudness summation and Frequency Resolution.
The additional measurements will include a loudness summation evaluation at
the electrode level as well as an acoustic and electric spectro-temporal
modulation test, speech understanding tests and subjective preference rating
for 4 alternative FATs.

To evaluate a new imaging based natural mapping strategy for CI fitting to
optimize patient-related outcomes. Compared to conventional clinical fitting,
it is proposed that this new method will improve speech understanding and sound
perception in adult CI patients during a follow-up period of 6 months.

CALF addendum:

To develop and evaluate spectral loudness summation and frequency resolution as
measures of neural health related to individual CI frequency mappings,
outcomes and preferences.

This study has multiple phases. The primary part is set up as a prospective
single blinded, daily randomized cross-over clinical trial. In this phase
electric hearing will be optimized. When patients retain the use of a
contralateral hearing aid, acoustic hearing optimization will be performed in a
second phase. During the third phase, patients receive their clinical fit,
which will be based on the preferences they have obtained during the study
period. More in detail, the study outline can be summarized as follows.

- Phase 1. During the intensive CI-rehabilitation phase, mapping of the
electrical input will be based on an individualized natural frequency alignment
as estimated with imaging methods. This natural fitting will be compared to the
standard frequency alignment. A daily randomization scheme will be applied
whereby the subject crosses over between CI fitting programs and thus
effectively acting as his own control, followed by a period of free choice
between both maps to incorporate patient preference. Outcome measures will be
assessed at several single points, to address the difference between both CI
maps, as well as over time, to address the learning curve with both CI maps.
- Phase 2. After a period of 6 months a stable outcome with CI is expected.
When patients retain the use of a contralateral hearing aid up to this time
point, the fitting of the acoustic hearing aid will be optimised and compared
to the standard fitting. Outcome measures will be assessed acutely and at the
end of a take-home period.
- Phase 3. At this time point, patients have indicated their final preference
for either the conventional or bimodal HA fitting. In combination with the
preferred CI settings, as indicated at the end of phase 1, a clinical fit will
be performed for both CI and HA.

CALF addendum:

The measurements for CALF will be performed in an additional test session
between 12 and 48 months after CI activation.

Two interventions will be implemented during the study.

1. During the intensive CI-rehabilitation phase, mapping of the electrical
input will be based on an individualized natural frequency alignment as
estimated with imaging methods. This natural fitting will be compared to the
standard frequency alignment. A daily randomization scheme will be applied
whereby the subject acts as his own control, followed by a period of free
choice between both maps. Outcome measures will be assessed at several single
points, to address the difference between both CI maps, as well as over time,
to address the learning curve with both CI maps.

2. In a second stage, after a stable outcome with CI is reached and if a
contralateral hearing aid is used, the fitting of the acoustic hearing aid will
be optimised and compared to the standard fitting. Outcome measures will be
assessed acutely and at the end of a take-home period.

CALF addendum:

No further intervention will take place. Both the natural, standard and two
additional fittings will be tested only in an acute setting.

There are no substantial health risks specifically associated with study
participation. There is one additional cone beam CT scan associated with a low
radiation dosage. CE-marked hearing equipment (CI and HA) is used within the
scope of standard care. Participation however takes time, effort and attention
from subjects. Specifically, patients will train two CI fitting programs over
one in standard clinical care. This may either be a disadvantage or a benefit.
In case it would be a disadvantage, the risk and burden would be limited to 6
months, after which the effects of the double fitting can be expected to wash
out. Patients have to come to the hospital for extra test sessions. As a result
of the study, subjects may or may not choose the continued use of the new
fitting strategy of their hearing equipment to improve their performances as
far as the standard clinical sound processors support it. In the case of
promising results, manufacturer Advanced Bionics may apply the concept of
natural fitting to clinical use thereby improving patient-related care in CI
rehabilitation. Recruitment will be performed in a standard pool of
CI-patients, thereby making study results directly applicable to clinical care.

CALF addendum:

No additional health risks associated with study participation. Patients will
come to the hospital for a test session which will last for a maximum of 4
hours.