Optimizing Bilateral and Single-sided-deafness Cochlear Implants for Functioning in Complex Auditory Environments - Part 2
Overview
- Phase
- Not Applicable
- Intervention
- Not specified
- Conditions
- Hearing Loss
- Sponsor
- University of Maryland, College Park
- Enrollment
- 300
- Locations
- 2
- Primary Endpoint
- Computed-tomography scan
- Status
- Enrolling By Invitation
- Last Updated
- last year
Overview
Brief Summary
Cochlear implants (CIs) are devices that partially restore hearing for people with severe to profound hearing loss. This research focuses on CI users who use bilaterally implanted devices (two CIs, one on each side) and also "single-sided deafness" (SSD) CI users who use one CI together with good acoustic hearing in their opposite ear. The goal is to measure and understand the impact of large input asymmetries across the two ears. These asymmetries are common in BI-CI listeners and always present in SSD-CI users. Although most CI listeners benefit from a second source of auditory input, this project measures how these asymmetries limit speech understanding and spatial hearing. The long-term goal is countering or compensating for input asymmetries. Electrophysiological measures are used to describe the health of the auditory system. Behavioral measures are used to assess if training improves performance. CT imaging is utilized to describe the placement of the CIs.
Investigators
Matthew Goupell
Professor, Department of Hearing and Speech Sciences
University of Maryland, College Park
Eligibility Criteria
Inclusion Criteria
- •two cochlear implants
- •acquired their hearing loss during adulthood or late childhood (post-lingual onset)
- •native English speaker
- •primarily use oral language
- •at least six months of cochlear implant use
- •Sufficient corrected or uncorrected visual acuity (20/50 or better) to read large-font text
Exclusion Criteria
- •people who do not use oral language will be excluded.
- •people with less than six months of device use will be excluded
- •other known disability or neurological disorder
- •women who are pregnant will be excluded from the CT portion of the study
- •people with any unaided audiometric tone-detection threshold better than 60 dB HL at standard audiometric frequencies (250-8000 Hz) in either ear will be excluded
- •For Unilateral Cochlear Implant User with Single-Sided Deafness Arm:
- •Inclusion Criteria:
- •one cochlear implant in one ear and a second ear with some acoustic hearing
- •acquired their hearing loss during adulthood or late childhood (post-lingual onset)
- •native English speaker
Outcomes
Primary Outcomes
Computed-tomography scan
Time Frame: For CI users: CT scan will be collected from existing medical records with permission or taken after study enrollment. Measurements taken after study enrollment. Not collected for non-implanted listeners with acoustic hearing.
A computed tomography temporal bone scan will be used to image the cochlear structures and cochlear implant electrode array located within. This scan will use a standard clinical scanner, with software updated to extend the Hounsfield range to reduce artifact from the metal contacts of the electrode array. This procedure uses radiographic processes, and therefore presents the subject with a safe but nonzero amount of radiation. The CT scan will be analyzed to provide measurements of each array's insertion depth within the cochlea (in degrees and mm), the distance to the cochlear modiolus (mm), and cochlear scalar location.
Electrode impedance (transelectrode impedance matrix)
Time Frame: Post-treatment - after at least 6 months use of a cochlear implant if CI user. Not collected for non-implanted listeners with acoustic hearing.
This standard clinical measurement will apply a current to one electrode, and measure the resulting induced voltage at each of the other electrodes in the array, one at a time. This process uses low-level electrical stimulation only intended to measure the impedance of the intervening tissues and fluids of the cochlea, and is rarely even perceived by the subject.
Perceptual responses to sound level
Time Frame: Post-treatment - after at least 6 months use of a cochlear implant if CI user. After enrollment for non-implanted listeners with acoustic hearing.
Interaural loudness mismatch is defined as the difference between the levels required to balance interaural loudness for sequential stimulation and the levels required to perceptually center a sound image in space for simultaneous stimulation. Participants will respond through pressing virtual buttons on a computer screen. Depending on the condition tested, the sounds will be delivered to one or both ears.
Speech understanding in the presence of masking sounds
Time Frame: Post-treatment - after at least 6 months use of a cochlear implant if CI user. After enrollment for non-implanted listeners with acoustic hearing.
Speech understanding will be assessed as the percentage of correctly identified keywords. Subjects will respond through oral report (where the responses will be scored by the experimenter) or through pressing virtual buttons on a computer screen. The speech sounds will be delivered to one or both ears in the presence of different types of masking sounds. In some cases, signal processing techniques will be used to distort the speech signals to simulate asymmetric hearing abilities.
Electrically evoked compound action potentials (ECAPs)
Time Frame: Post-treatment - after at least 6 months use of a cochlear implant if CI user. Not collected for non-implanted listeners with acoustic hearing.
Electrically evoked compound action potentials (ECAPs) will be measured using clinically-available software to track the growth in auditory nerve response (observed \~0.2-0.8 ms post-stimulus onset) as input level is varied from threshold to the maximal level at which the signal is comfortably loud. The slope of input-output function will be measured ( in microvolts/current unit) for each electrode along the electrode array of each cochlear implant study participant.
Secondary Outcomes
- Perceptual Fusion(Post-treatment - after at least 6 months use of a cochlear implant if CI user. After enrollment for non-implanted listeners with acoustic hearing.)
- Sound Localization(Post-treatment - after at least 6 months use of a cochlear implant if CI user. After enrollment for non-implanted listeners with acoustic hearing.)
- Spectrotemporal ripple sensitivity(Post-treatment - after at least 6 months use of a cochlear implant if CI user. After enrollment for non-implanted listeners with acoustic hearing.)