Cochlear*s Direct Acoustic Cochlear Stimulator Investigational Device (C-DACS ID) clinical trial CAG5229

One of the common causes leading to conductive hearing loss is otosclerosis. In
general, otosclerosis leads to a fixation of the stapes footplate to the oval
window of the cochlea. This generally impairs movement of the stapes and
therefore transmission of sound into
the inner ear. Otosclerosis is predominantly a Caucasian disease. Its
prevalence lies between 0.1% and 1% with a mean prevalence of 0.3%. The
incidence of otosclerosis is approximately two times higher in woman than in
men. Usually noticeable hearing loss begins between the
age of 15 and 45, but can start sooner . In most cases the disease is
bilateral. 75% of patients have additional tinnitus.
Despite intensive research. the aetiology of otosclerosis is not fully
understood. Treatment of otosclerosis relies on two primary options: hearing
aids (more recently including Baha) or stapes surgery. Hearing aids are usually
very effective early in the course of the disease, but
eventually a stapedectomy may be required for definitive treatment.
Stapedectomy is indicated when the stapes is firmly fixed, as demonstrated by
an air-bone gap of at least 30 dB for the speech frequencies and a negative
Rinne test. If the conductive component of a mixed hearing loss is still quite
small (< 30 dB) hearing aids can be used to compensate for both components of
the hearing loss. But the need for high amplification can drive even the most
powerful hearing aids to their limits and introduce problems with distortion.
If the conductive component of a mixed hearing loss is still quite small (< 30
dB) hearing aids can be used to compensate for both components of the hearing
loss. But the need for high amplification can drive even the most powerful
hearing aids to their limits and introduce problems with distortion
Implantable hearing aids are commercially available since a few years. They
were originally developed for the compensation of sensorineural hearing losses
and to remove problems with stigma, occlusion and discomfort. Lately,
implantable hearing aids are also used to compensate for conductive or mixed
hearing losses.
A middle ear implant consists of two parts, a subcutaneous receiver and a
transducer which is attached to the stapes or incus. An external soundprocessor
is carried. In this way sounds are transferred to the middle ear without the
need to occlude the external ear canal.
With the newly developed system of direct acoustic cochlear stimulation (DACS)
a middle ear implant is placed in combination with the prosthesis of
stapedotomy the surgery. The prosthesis is not attached to the body of the
incus but on a artificial incus. In this way a solution can be put forward for
patients with mixed hearing loss involving the conductive component (using the
prosthesis) and the perceptive component (using the C-DACS system).

The basic safety of the surgical procedure and the DACS actuator as well as the
basic efficacy of the DACS were already shown in the DACS Chronic Clinical
Trial (see protocol). The safety of the C-DACS ID receiver/stimulator, which
replaces the percutaneous plug, is shown since many years in CE marked cochlear
implants. The C-DACS Clinical Trial has three main objectives. The first trial
objective is to confirm the clinical
efficacy of the C-DACS ID in subjects with severe to profound mixed hearing
loss. This will be done by measuring and analyzing the aided free field hearing
thresholds and aided speech discrimination scores post-operatively.
The second trial objective it to investigate a new fitting algorithm for the
C-DACS ID. The new fitting algorithm is based on the expected most comfortable
level of the subject, calculated with the in-situ thresholds and in-situ UCL
measured during the fitting procedure. The new fitting algorithm is expected to
deliver a good first impression of the sound quality at the activation of the
C-DACS ID. Also, it is expected that the subjects will have a good speech
understanding with the new fitting algorithm. This shall be proven by analyzing
the aided free field hearing thresholds and aided speech discrimination scores
post-operatively.
The third trial objective is to confirm the safety of the C-DACS ID in subjects
with severe to profound mixed hearing loss. On the one hand this will be done
by measuring and analyzing the bone conduction thresholds 3-months
post-activation. On the other hand all surgical complications related to the
procedure and all post-operative complication related to the device will be
analyzed and reported.

The clinical investigation is designed as a prospective, open, multi-center
study in up to 10 patients.
Study centers are the Medizinische Hochschule Hannover (MHH) in Hanover/Germany
and the UMC
St. Radboud in Nijmegen/The Netherlands.
The C-DACS ID will be implanted in combination with a traditional stapedotomy
surgical procedure.

A regular stapedotomy will be performed in combination with a mastoidectomy, a
posterior tympanotomy and the placement of the experimental C-DACS ID device.

Burden
The participants will visit the clinic at least 5 times voor audiometric
evaluation, activation and adjustement of the middle ear implant. After
implantation by surgery a short stay at the ward is necessary.

Benefits
Subject benefits are anticipated to be:
· Improvement of hearing sensitivity
· Improvement of speech understanding
· Improvement of sound quality
· Improvement of quality of life
· No occlusion of ear canal

Risks
· Study subjects are exposed to the normal risks associated with surgery and
general anaesthesia.
· Study subjects are exposed to the risks associated with standard stapes
surgery.
· Study subjects are also exposed to the risks associated with standard
mastoidectomy which
can cause additional risks like injury of the sigmoid sinus, jugular bulb, and
dura; and
cerebrospinal fluid leakage.
·The C-DACS ID results in a palpable lump under the skin just behind the ear.
Thiscause irritation, inflammation or breakdown of the skin and,
in some cases, extrusion of the device.
· Mechanical stimulation of the inner ear may result in temporary or permanent
loss of hearing sensitivity or increased sensorineural hearing loss, increased
tinnitus, dizziness or pain. The long term effect of mechanical stimulation of
the cochlea is unknown.
· Failure of component parts (both external and internal) could result in the
perception of an uncomfortably loud sound sensation, no sound or pain. Tissue
damage could occur.
· Over-stimulation of the ear might occur, causing brief unpleasant sensations.
· The implanted device can cause inflammatory (allergic) reactions which might
lead to medicaltreatment, hospitalization, and, in the worst case, removal of
the device.
· External impact on a certain point on the head can cause the stapes
prosthesis to move inwards, which might cause dizziness, pain, tinnitus, and,
in the worst case, damage of inner or middle ear structures, which might lead
to partial or complete loss of residual hearing.