Electrode Placement and Audiologic Outcomes With the Advanced Bionics HiFocus L23 Electrode

Cochlear implants (CI) are biomechanical sense prostheses approved by the FDA for the
treatment of sensorineural hearing loss. CI's function by bypassing the absent or
dysfunctional cochlear end organs to directly electrically stimulate the spiral ganglion and
cochlear nerve. A variety of commercially available FDA-approved implants exist for the
treatment of severe to profound deafness. Implants are typically designed in two broad
categories: lateral wall electrodes and perimodiolar. Perimodiolar electrodes are precurved
electrodes that are designed to hug the center of the cochlea (modiolus) after insertion.
Lateral wall electrodes are slim and straight, hugging the lateral wall on insertion.

Recent studies have shown that electrode design and location within the cochlea impact
patient performance. Specifically, electrodes located completely within the scala tympani are
associated with better outcomes than those that cross over from the scala tympani to the
scala vestibuli during insertion. The same study has shown that lateral wall electrodes are
less likely than perimodiolar electrodes to have scalar excursion to the scala vestibuli.
Location matters with these implants because electrode position completely within the scala
tympani is associated with higher rates of preservation of residual hearing. Minimizing
cochlear trauma allows for preservation of residual acoustic hearing particularly in low
frequencies. While this low frequency hearing is of little benefit independently, when
combined with the electrical stimulation from the cochlear implant patients have improved
performance.

The HiFocus L23 electrode is manufactured by Advanced Bionics (Valencia, California), and is
FDA approved for the treatment of sensorineural hearing loss in adult and pediatric patients.
It is designed as a slim and straight lateral wall electrode that can be inserted with low
force to minimize intracochlear trauma. While pre-market studies were performed by Advanced
Bionics as a part of its approval for use by the FDA, no post-market studies have been
performed to assess the audiologic outcomes, electrode location after insertion, and hearing
preservation rates when using this electrode. These aims will be accomplished through several
means. Audiologic speech performance will be assessed through a standardized
clinical/audiometric protocol currently followed by the Vanderbilt University Medical Center
cochlear implant team. Electrode location for all participants will be determined using novel
software created by Vanderbilt engineering faculty and graduate students that uses
computerized tomography (CT) images obtained as a part of practice postoperatively or
intraoperatively using an FDA approved Xoran xCAT® device, a portable flat panel volume
computerized tomography (fpVCT) machine (Vanderbilt) or regular CT scan at participating
institutions as applicable. These images can be registered to existing pre-operative
conventional CT scans and used to produce 3-dimensional models of electrode placement within
each patient's cochlea. This software is investigational and used in other research studies
for the same purpose.

The extent to which the electrode remains in the desired location (scala tympani) will then
be correlated with audiologic outcomes as obtained above. Residual hearing rates and quality
of life measures will be obtained as a part of audiologic testing.

If a fine resolution, high quality conventional head CT has been previously obtained, or is
obtained as part of routine care this scan may be used in place of the fpVCT or in addition
to the fpVCT scan. The option of having a conventional head CT performed in radiology for
research purposes in place of the fpVCT head CT scan will also be available.

Surgeons will complete surveys after each case concludes to evaluate the ease of insertion
and will record the insertion via standard recording techniques in the operating room that
are available for any microscopic case. These videos for all surgeries will be blinded and
reviewed at Vanderbilt for ease and speed of insertion.

Inclusion Criteria:

- Male or female 18 years of age and above.

- Sensorineural hearing loss meeting criteria for cochlear implants, assessed no greater
than three months prior to cochlear implant surgery

- Patient schedule to undergo CI surgery using Advanced Bionics SlimJ/L23 device.

- Ability to undergo adequate audiology follow-up or planned follow up for those
participants undergoing scanning in the OR.

- Competent in decision making process and able to read and sign a written informed
consent form.

- English language proficiency.

- If the patient has already had a fine resolution CT or a fpVCT of the head (more than
likely as a participant of another research study) the scan will not be repeated, the
images from the previous scan will be used for the purposes of this study.

- If the patient has undergone a conventional CT scan of the head after cochlear
implantation as part of their routine care, this scan may be used in place of the
research scan or in addition to the research scan.

Exclusion Criteria:

- Patients who weigh over 300 lbs (when Xoran xCAT headboard is being used). Otherwise,
weight is not exclusionary.

- Females who are pregnant. All females of child-bearing age in the study will undergo a
pregnancy test.