Long Term Outcomes After Vestibular Implantation
NCT Number: NCT06500975
Status: NOT_YET_RECRUITING
Study Type: OBSERVATIONAL
Conditions: Bilateral Vestibular Hypofunction|Bilateral Vestibular Deficiency|Bilateral Vestibulopathy|Gentamicin Ototoxicity|Aminoglycoside Toxicity|Vestibular Diseases|Sensation Disorders|Labyrinth Diseases|Other Disorders of Vestibular Function
Interventions: DEVICE: Labyrinth Devices MVI™ Multichannel Vestibular Implant System
Sponsor: Johns Hopkins University
Collaborators: National Institute on Aging (NIA)|National Institute on Deafness and Other Communication Disorders (NIDCD)|Labyrinth Devices, LLC
Sex: ALL
Age: ADULT, OLDER_ADULT
Enrollment: 32
Study Design: Observational Model: |Time Perspective: p
Start Date: 2024-09
Completion Date: 2029-12
Locations: Johns Hopkins School of Medicine, Baltimore, Maryland, 21287, United States

Summary:
Although cochlear implants can restore hearing to individuals who have lost cochlear hair cell function, there is no widely available, adequately effective treatment for individuals suffering chronic imbalance, postural instability and unsteady vision due to bilateral vestibular hypofunction. Prior research focused on ototoxic cases has demonstrated that electrical stimulation of the vestibular nerve via a chronically implanted multichannel vestibular implant can partially restore vestibular reflexes that normally maintain steady posture and vision; improve performance on objective measures of postural stability and gait; and improve patient-reported disability and health-related quality of life. This single-arm open-label study extends that research to evaluate outcomes for up to 8 individuals with non-ototoxic bilateral vestibular hypofunction, yielding a total of fifteen adults (age 22-90 years at time of enrollment) divided as equally as possible between ototoxic and non-ototoxic cases.

Primary Outcome Measures: PM1.1: Dynamic Gait Index (DGI)18 during motion-modulated implant stimulation at 4 years post-implantation, relative to pre-operative baseline, aggregated across all implant users., DGI comprises 8 gait tasks scored by an examiner: walking on a level surface, changing gait speed, walking during horizontal head turns, walking during vertical head turns, pivoting, stepping over an obstacle, stepping around obstacles, and waling up and down stairs. Each task is scored (0-3 points, 3 is best). Raw DGI score is the sum of the eight subtest scores and ranges from 0 to 24, with higher scores meaning better outcome and minimally important difference 3.2 points., 4 years post-implantation up to 5 years post-enrollment|PM1.2: Gain (VHITG) of the vestibulo-ocular reflex (VOR), as measured using the video head impulse test (vHIT), During video head impulse testing (vHIT), rotational eye and head movement are measured by a goggle-mounted camera and motion sensor during brief, fast \~10 degree head rotations about the axis of a semicircular canal being tested. Performance is quantified by vestibulo-ocular reflex (VOR) gain, which a ratio of eye movement to head movement (in this case the integral of eye velocity relative to the head and the additive inverse of the integral of head velocity, respectively). VHITG, the average vHIT VOR gain for each of the three semicircular canals of the implanted ear, typically ranges from 0 to 1, with higher numbers indicating better performance., 4 years post-implantation up to 5 years post-enrollment
Secondary Outcome Measures: EM1.1: Vestibular Implant Composite Outcome (VICO) score, Vestibular Implant Composite Outcome (VICO) score incorporates changes in vestibulo-ocular reflex gain during video head impulse testing, postural stability, gait, dizziness handicap, and health-related quality of life at 4 years post-implantation, relative to pre-operative baseline. VICO (t=6months post-op) score is the sum of changes, from preoperative baseline to 4 years post-implantation, in vestibulo-ocular reflex gain during passive head impulse rotation (VHITG); postural stability as quantified by the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition Balance Subtest 5 (BOT); gait stability as quantified by Dynamic Gait Index (DGI); Dizziness Handicap Inventory (DHI); and SF6D health utility (SF6DU); with each component's contribution scaled to the corresponding test's minimally important difference (MID). Score 0-100, higher scores indicate better outcomes., 4 years post-implantation up to 5 years post-enrollment|EM1.2: Bruininks-Oseretsky Test of Motor Proficiency 2nd Edition Balance Subtest 5 (BOT) score., BOT comprises 9 postural tasks scored by an examiner: standing with both feet on a line, standing on one leg, tandem walking, walking on a line with eyes open and eyes closed, and standing on a balance beam. Each task is performed twice and scored (0-4 points, 4 is best). The BOT score is the sum of the best scores for each task. It ranges from 0 to 36 points, with higher scores meaning better outcome and minimally important difference 4.5 points., 4 years post-implantation up to 5 years post-enrollment|EM1.3: Dizziness Handicap Inventory (DHI), Dizziness Handicap Inventory (DHI) is a 25-question survey designed to quantify self-rated disability due to dizziness and unsteadiness, with scores ranging from 0 (least disabled, best outcome) to 100 (worst outcome). The minimally important difference is 18 points., 4 years post-implantation up to 5 years post-enrollment|EM1.4: SF6D utility (SF6DU) score, SF6DU is a unitless health utility score computed from patient-reported replies to the SF6 health-related quality of life survey and ranging from 0 to 1, with higher scores meaning better outcome and minimally important difference 0.03 points., 4 years post-implantation up to 5 years post-enrollment|EM2.1: Vestibular Implant Composite Outcome (VICO) score, Vestibular Implant Composite Outcome (VICO) score incorporates changes in vestibulo-ocular reflex gain during video head impulse testing, postural stability, gait, dizziness handicap, and health-related quality of life at 4 years post-implantation, relative to pre-operative baseline. VICO (t=6months post-op) score is the sum of changes, from preoperative baseline to 4 years post-implantation, in vestibulo-ocular reflex gain during passive head impulse rotation (VHITG); postural stability as quantified by the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition Balance Subtest 5 (BOT); gait stability as quantified by Dynamic Gait Index (DGI); Dizziness Handicap Inventory (DHI); and SF6D health utility (SF6DU); with each component's contribution scaled to the corresponding test's minimally important difference (MID). Score 0-100, higher scores indicate better outcomes., 4 years post-implantation up to 5 years post-enrollment|EM2.2: Bruininks-Oseretsky Test of Motor Proficiency 2nd Edition Balance Subtest 5 (BOT), BOT includes 9 postural tasks scored by an examiner: standing with both feet on a line, standing on one leg, tandem walking, walking on a line with eyes open and eyes closed, and standing on a balance beam. Each task is performed twice and scored (0-4 points). The BOT score is the sum of the best scores for each task. It ranges from 0 to 36 points, with higher scores meaning better outcome and minimally important difference 4.5 points., 4 years post-implantation up to 5 years post-enrollment|EM2.3: Dizziness Handicap Inventory (DHI), Dizziness Handicap Inventory (DHI) is a 25-question survey designed to quantify self-rated disability due to dizziness and unsteadiness, with scores ranging from 0 (least disabled, best outcome) to 100 (worst outcome). The minimally important difference is 18 points., 4 years post-implantation up to 5 years post-enrollment|EM2.4: SF6D utility (SF6DU) score, SF6DU is a unitless health utility score computed from patient-reported replies to the SF6 health-related quality of life survey and ranging from 0 to 1, with higher scores meaning better outcome and minimally important difference 0.03 points., 4 years post-implantation up to 5 years post-enrollment|EM2.5: Dynamic Gait Index (DGI), DGI comprises 8 gait tasks scored by an examiner: walking on a level surface, changing gait speed, walking during horizontal head turns, walking during vertical head turns, pivoting, stepping over an obstacle, stepping around obstacles, and waling up and down stairs. Each task is scored (0-3 points, 3 is best). Raw DGI score is the sum of the eight subtest scores and ranges from 0 to 24, with higher scores meaning better outcome and minimally important difference 3.2 points., 4 years post-implantation up to 5 years post-enrollment|EM2.6: Gain (VHITG) of the vestibulo-ocular reflex (VOR), as measured using the video head impulse test (vHIT) and averaged for the three implanted semicircular canals, During video head impulse testing (vHIT), rotational eye and head movement are measured by a goggle-mounted camera and motion sensor during brief, fast \~10 degree head rotations about the axis of a semicircular canal being tested. Performance is quantified by vestibulo-ocular reflex (VOR) gain, which a ratio of eye movement to head movement (in this case the integral of eye velocity relative to the head and the additive inverse of the integral of head velocity, respectively). VHITG, the average vHIT VOR gain for each of the three semicircular canals of the implanted ear, typically ranges from 0 to 1, with higher numbers indicating better performance., 4 years post-implantation up to 5 years post-enrollment|EM3.1: Vestibular Implant Composite Outcome (VICO) score at 4 years post-implantation, relative to pre-operative baseline, for the subgroup of participants who have ototoxic adult-onset BVH., Vestibular Implant Composite Outcome (VICO) score incorporates changes in vestibulo-ocular reflex gain during video head impulse testing, postural stability, gait, dizziness handicap, and health-related quality of life at 4 years post-implantation, relative to pre-operative baseline. VICO (t=6months post-op) score is the sum of changes, from preoperative baseline to 4 years post-implantation, in vestibulo-ocular reflex gain during passive head impulse rotation (VHITG); postural stability as quantified by the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition Balance Subtest 5 (BOT); gait stability as quantified by Dynamic Gait Index (DGI); Dizziness Handicap Inventory (DHI); and SF6D health utility (SF6DU); with each component's contribution scaled to the corresponding test's minimally important difference (MID). Score 0-100, higher scores indicate better outcomes., 4 years post-implantation up to 5 years post-enrollment|EM3.2: Bruininks-Oseretsky Test of Motor Proficiency 2nd Edition Balance Subtest 5 (BOT) score 4 years post-implantation, relative to pre-operative baseline, for the subgroup of participants who have ototoxic adult-onset BVH., BOT includes 9 postural tasks scored by an examiner: standing with both feet on a line, standing on one leg, tandem walking, walking on a line with eyes open and eyes closed, and standing on a balance beam. Each task is performed twice and scored (0-4 points). The BOT score is the sum of the best scores for each task. It ranges from 0 to 36 points, with higher scores meaning better outcome and minimally important difference 4.5 points., 4 years post-implantation up to 5 years post-enrollment|EM3.3: Dizziness Handicap Inventory (DHI) score at 4 years post-implantation, relative to pre-operative baseline, for the subgroup of participants who have ototoxic adult-onset BVH., Dizziness Handicap Inventory (DHI) is a 25-question survey designed to quantify self-rated disability due to dizziness and unsteadiness, with scores ranging from 0 (least disabled, best outcome) to 100 (worst outcome). The minimally important difference is 18 points., 4 years post-implantation up to 5 years post-enrollment|EM3.4: SF6D utility (SF6DU) score at 4 years post-implantation, relative to pre-operative baseline, for the subgroup of participants who have ototoxic adult-onset BVH., SF6DU is a unitless health utility score computed from patient-reported replies to the SF6 health-related quality of life survey and ranging from 0 to 1, with higher scores meaning better outcome and minimally important difference 0.03 points., 4 years post-implantation up to 5 years post-enrollment|EM3.5: Dynamic Gait Index (DGI) score at 4 years post-implantation, relative to pre-operative.baseline, for the subgroup of participants who have ototoxic adult-onset BVH., DGI comprises 8 gait tasks scored by an examiner: walking on a level surface, changing gait speed, walking during horizontal head turns, walking during vertical head turns, pivoting, stepping over an obstacle, stepping around obstacles, and waling up and down stairs. Each task is scored (0-3 points, 3 is best). Raw DGI score is the sum of the eight subtest scores and ranges from 0 to 24, with higher scores meaning better outcome and minimally important difference 3.2 points., 4 years post-implantation up to 5 years post-enrollment|EM3.6: Gain (VHITG) of the vestibulo-ocular reflex, measured using the video head impulse test.averaged for the three implanted semicircular canals, relative to pre-operative baseline, for the subgroup of participants who have ototoxic adult-onset BVH., During video head impulse testing (vHIT), rotational eye and head movement are measured by a goggle-mounted camera and motion sensor during brief, fast \~10 degree head rotations about the axis of a semicircular canal being tested. Performance is quantified by vestibulo-ocular reflex (VOR) gain, which a ratio of eye movement to head movement (in this case the integral of eye velocity relative to the head and the additive inverse of the integral of head velocity, respectively). VHITG, the average vHIT VOR gain for each of the three semicircular canals of the implanted ear, typically ranges from 0 to 1, with higher numbers indicating better performance., 4 years post-implantation up to 5 years post-enrollment|SM0: Type, incidence and severity of unanticipated adverse device effects as of 4 years post-implantation, Assess safety of the intervention, aggregating data across all implanted participants (diversified across ototoxic and non-ototoxic/non-central adult-onset BVH), as determined by incidence of adverse device-related events from pre-intervention to 4 years post-implantation., 4 years post-implantation up to 5 years post-enrollment|SM1.1: implant-side bone-conduction 4-frequency (0.5, 1, 2, 4 kHz) pure tone average detection threshold (BonePTAi), BonePTAi is the 4-frequency average of pure tone detection thresholds, in dBHL, for implant-side bone-conduction presentation of pure tones at 0.5, 1, 2 and 4 kHz. Range is -10 to 80 dBHL, with change toward smaller absolute values representing better (closer to normal) outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.2: implant-side air-conduction 4-frequency pure tone average detection threshold (AirPTAi), AirPTAi is the 4-frequency average of pure tone detection thresholds, in dBHL, for implant-side air-conduction presentation of pure tones at 0.5, 1, 2 and 4 kHz. Range is -10 to 120 dBHL, with change toward smaller absolute values representing better (closer to normal) outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.3: implant-side consonant-nucleus-consonant word discrimination score (CNCWi), CNCWi is the percentage of monosyllabic consonant-nucleus-consonant words correctly repeated when presented via an earphone speaker on the implanted side in a sound-isolation booth while a masking noise is played to the contralateral ear at 40 dB above its bone-conduction 4-frequency pure tone detection threshold if that threshold is at least 10 dB better than that of the ear being tested. CNCWi ranges from 0-100% correct, with higher score meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.4: sound-field Arizona Biology (AzBios)27 sentences-in-noise discrimination score, AzBios is the percentage of words correctly repeated when a set of 20 Arizona Biology sentences (randomly chosen without repeats from 15 sets) is presented at a moderate level (60 dB SPL) along with masking noise (simultaneous presentation of ten sentences from another set at aggregate sound level 55 dBSPL) to both ears via a sound field speaker in a sound-isolation booth. Scores range from 0-100% correct, with higher score meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.5: Proportion of implanted ears that maintain American Academy of Otolaryngology - Head & Neck Surgery (AAO-HNS) 1995 Class A or B hearing13 or ≤ 30 dB change from preoperative baseline (if preoperative baseline is ≥20 dBHL) and ear-specific speech, For ClassABCNCW, AAO-HNS (American Academy of Otolaryngology - Head \& Neck Surgery) 1995 Class A or B hearing is defined as AirPTAi not worse than 50 dBHL and CNCWi not worse than 50%. ClassABCNCW proportion ranges from 0-100%, with higher values meaning better outcomes., 4 years post-implantation up to 5 years post-enrollment|SM1.6: Proportion of implanted participants who maintain AAO-HNS 1995 Class A or B hearing or ≤ 30 dB change from preoperative baseline (if preoperative baseline is ≥20 dBHL) and ear-specific speech discrimination ≤30% worse than preoperative baseline, For ClassABAzBio, AAO-HNS (American Academy of Otolaryngology - Head \& Neck Surgery) 1995 Class A or B hearing is defined as AirPTAi not worse than 50 dBHL and sound-field-presentation Arizona Biology sentences-in-noise discrimination score (AzBios) not worse than 50%. ClassABAzBio proportion ranges from 0-100%, with higher values meaning better outcomes., 4 years post-implantation up to 5 years post-enrollment|SM1.7: implant-side distortion-product otoacoustic emissions, Distortion-product otoacoustic emissions (DPOAE) are sounds generated by a normal cochlea and detectable using a microphone in the ear canal when pairs of pure tones (centered on 0.75, 1, 1.5, 2, 3, 4, 6 and 8 kHz) are presented to the ear. DPOAE signals (and 8-valued vector for responses to stimuli centered on 0.75, 1, 1.5, 2, 3, 4, 6 and 8 kHz) are quantified in dB relative to the frequency-specific noise floor recorded by the same microphone before onset of stimulation. Response range is 0-15 dB, with higher values meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.8: Ear canal acoustic admittance as assessed by implant-side tympanometry, Tympanometry involves using an ear canal microphone to measure ear canal acoustic admittance (conventionally reported in units of mL) and volume (in mL) by sensing reflection of a 226 Hz tone presented via a speaker in the ear canal while ear canal pressure is slowly varied from -400 to 200 decaPascals. Negative bias pressures pull the ear drum outward, positive bias pressures push the ear drum inward, and acoustic admittance is greatest when the ear drum is in a neutral anatomic position, neither retracted inward nor ballooned outward. Results are conventionally represented graphically then summarized by a three-valued vector comprising peak compliance (range 0-2 milliliters (mL), values closer to normal range of 0.3-1.4 mL meaning more normal outcome), pressure at which compliance peaks (range -400 to 200 decaPascal, values closer to 0 meaning more normal outcome), and ear canal volume (range 0-3 mL, values closer to normal adult range of 0.6-1.4 meaning more normal outcome)., 4 years post-implantation up to 5 years post-enrollment|SM1.9: Tinnitus Handicap Inventory (THI), The Tinnitus Handicap Inventory (THI) survey is set of questions designed to quantify self-perceived handicap due to tinnitus. THI score ranges from 0-100. Higher scores mean worse outcome., 4 years post-implantation up to 5 years post-enrollment|SM1.10: Autophony Index (AI), The Autophony Index (AI) survey is set of questions designed to quantify self-perceived autophony (hearing one's voice or other internally-generated body sounds). AI score ranges from 0-104. Higher scores mean worse outcomes., 4 years post-implantation up to 5 years post-enrollment|SM1.11: cervical vestibular-evoked myogenic potential (cVEMP) response amplitude, Cervical vestibular-evoked myogenic potentials (cVEMPs) are a measure of saccule-mediated inhibition of sternocleidomastoid muscle electromyographic (EMG) activity during presentation of loud tones to the ipsilateral ear. After normalizing to average rectified EMG activity (in microvolts) prior to sound stimulation, cVEMP amplitudes (in microvolts) are unitless. Values range from 0 to \~10, with larger values suggesting increased saccule activity and generally indicating better outcomes, except that values above 3.0 suggest abnormally high saccule sensitivity to sound., 4 years post-implantation up to 5 years post-enrollment|SM1.12: ocular vestibular-evoked myogenic potential (oVEMP) response amplitude, Ocular vestibular-evoked myogenic potentials (oVEMPs) are a measure of utricle-mediated electromyographic (EMG) activity of inferior oblique and inferior rectus extraocular muscles during presentation of loud tones to the contralateral ear. Amplitude ranges from 0 to \~50 microvolts, with larger values generally suggesting increased utricle activity and better outcomes but values above 17 microvolts suggesting abnormally high utricle sensitivity to sound., 4 years post-implantation up to 5 years post-enrollment|SM1.13: subjective visual vertical (SVV) as assessed using the Bucket Test, A participant's vision is occluded by a bucket oriented so that its axis aligns with the participant's nasooccipital axis. The examiner rotates the bucket about the axis to a new orientation, the participant reorients it until a line drawn on the floor of the bucket is judges by the participant to be Earth-vertical and deviation of that line from true vertical is recorded. Values range over -15 to 15 degrees, with smaller absolute values meaning more normal outcomes., 4 years post-implantation up to 5 years post-enrollment|SM1.14: scalp thickness at the location of implanted magnets (Tscalp), Scalp thickness at the location of implanted magnets (Tscalp) is measured in mm using a magnetic sensor. Range is 0 to 10 mm, with values closer to the range 3-7mm indicating better outcomes., 4 years post-implantation up to 5 years post-enrollment|SM1.15: all adverse events, including but not limited to events related to the surgical procedure, device and device systems, Assess safety of the intervention, aggregating data across all implanted participants (diversified across ototoxic and non-ototoxic/non-central adult-onset BVH), as determined by changes in hearing and otolith endorgan function indicated by changes in all adverse events, including but not limited to events related to the surgical procedure, device and device systems., 4 years post-implantation up to 5 years post-enrollment|TM1: Proportion of all implanted participants who continue to use the MVI system daily at 4 years post-implantation, Assess tolerance of the intervention, aggregating data across all implanted participants, as determined by the proportion of all implant recipients who continue to use the MVI system daily at 4 years post-implantation., 4 years post-implantation up to 5 years post-enrollment|TM2: Proportion of implanted participants with non-ototoxic/non-central adult-onset BVH who continue to use the MVI system daily at 4 years post-implantation, Assess tolerance of the intervention, for the subgroup of participants who have non-ototoxic/non-central adult-onset BVH, as determined by the proportion of implanted participants with non-ototoxic/non-central adult-onset BVH who continue to use the MVI system daily at 4 years post-implantation., 4 years post-implantation up to 5 years post-enrollment|TM3: Proportion of implanted participants with ototoxic adult-onset BVH who continue to use the MVI system daily at 4 years post-implantation, Assess tolerance of the intervention, for the subgroup of participants who have ototoxic adult-onset BVH, as determined by the proportion of implanted participants with ototoxic adult-onset BVH who continue to use the MVI system daily at 4 years post-implantation., 4 years post-implantation up to 5 years post-enrollment
Other Outcome Measures: XM1.1 (A,B,C): VOR latency during VHIT, Vestibulo-ocular reflex (VOR) latency is measured in milliseconds for responses during video head impulse testing (described in 2.EM1.1) with study device providing three different modes of prosthetic vestibular nerve stimulation (A=motion-modulated/ treatment-mode stimulation, B=constant/placebo-mode stimulation, or C=no stimulation). Results are reported as a three-element vector of latencies relative to preoperative baseline (latency during mode A stimulation at 4 yr post-implantation, latency during mode B stimulation at 4 yr post-implantation, latency during mode C stimulation at 4 yr post-implantation). Latencies range from 0-1000 ms, smaller values meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|XM1.2 (A,B,C): saccade latency during VHIT, Saccade (VOR) latency is measured in milliseconds for responses during video head impulse testing (described in 2.EM1.1) with study device providing three different modes of prosthetic vestibular nerve stimulation (A=motion-modulated/ treatment-mode stimulation, B=constant/placebo-mode stimulation, or C=no stimulation). Results are reported as a three-element vector of latencies relative to preoperative baseline (latency during mode A stimulation at 4 yr post-implantation, latency during mode B stimulation at 4 yr post-implantation, latency during mode C stimulation at 4 yr post-implantation). Latencies range from 0-1000 ms, smaller values meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|XM2.1 (A,B,C): VOR gain-time constant product during whole-body yaw rotary chair velocity step rotations toward the implanted ear, A participant sits on a chair atop an Earth-vertical-axis rotating motor in darkness, wearing goggles that contain a camera to monitor eye rotation. The motor rotates at 240 deg/s for 1 min toward the implanted side. Slow phase nystagmus velocity is measured. Vestibulo-ocular reflex gain-time constant product GainTc is computed by multiplying gain (ratio of peak slow phase eye speed to peak chair speed) by time constant (duration after which the eye movement speed has decayed to 37% of its initial peak). GainTc ranges from 0 to 60 sec. Higher values mean better outcomes. It is measured and reported for responses during rotating chair testing with study device providing three different modes of prosthetic vestibular nerve stimulation (A=motion-modulated/ treatment-mode stimulation, B=constant/placebo-mode stimulation, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM2.2 (A,B,C): VOR frequency response during whole-body yaw rotary chair sinusoidal rotations, A participant sits on a chair atop an Earth-vertical-axis rotating motor in darkness, wearing goggles that contain a camera to monitor eye rotation. The motor rotates sinusoidally at 100 deg/s peak velocity and frequency 0.05/0.1/0.2/0.5/1 Hz. Slow phase nystagmus velocity is measured. The frequency response is a 5-element vector (one per stimulus frequency) of complex numbers, each comprising a unitless gain (eye velocity amplitude divided by chair velocity amplitude) and phase equal to 360 deg times ratio (time from peak eye velocity to peak head velocity)/(period of sinusoidal stimulus). Each gain ranges from 0 to 1; higher values mean better outcome. Each phase ranges from -180 to 180; values nearer zero mean better outcome. Frequency response is reported as a 3x5 matrix of values relative to preoperative baseline for testing with study device providing three modes of vestibular nerve stimulation: A=motion-modulated, B=constant-rate, C=off., 4 years post-implantation up to 5 years post-enrollment|XM3.1: electrically-evoked vestibulo-ocular reflex (eeVOR) response peak magnitude for largest response on each electrode, A participant sits on a motionless chair atop in darkness, wearing goggles that contain a camera to monitor eye rotation. The vestibular implant's stimulator delivers a series of electrical pulse trains to the inner via each electrode, one at a time. Slow phase nystagmus velocity is measured using the camera. For each canal, the largest measured nystagmus velocity is recorded. Velocities are reported as a 3-valued vector (the highest peak velocity measured for each of the three semicircular canals in the implanted ear), with values ranging from 0-300 deg/s and higher values meaning better outcomes., 4 years post-implantation up to 5 years post-enrollment|XM3.2: electrically-evoked vestibulo-ocular reflex (eeVOR) response 3D misalignment for largest response on each electrode, A participant sits on a motionless chair atop in darkness, wearing goggles that contain a camera to monitor eye rotation. The vestibular implant's stimulator delivers a series of electrical pulse trains to the inner via each electrode in each semicircular canal, one at a time. Slow phase nystagmus velocity is measured using the camera. For each canal, 3-dimensional (3D) misalignment (the angle in degrees between the 3D axis of peak velocity eye rotation and the 3D axis of the targeted semicircular canal) is measured for the peak nystagmus elicited by each electrode and stimulus intensity. 3D misalignment is reported as a 3-valued vector (the misalignment angles measured for each of the three semicircular canals in the implanted ear, using the electrodes and stimulus intensities that yield the largest responses approximately aligned with the target canal's axis), with values ranging from 0-180 deg and smaller values meaning better outcomes., 4 years post-implantation up to 5 years post-enrollment|XM4 (A,B,C): time to failure on Modified Romberg Test with Eyes Closed on Foam, The Modified Romberg Test with Eyes Closed on Foam involves having the participant stand for as long as possible on a foam pad with feet together, arms crossed, and eyes closed. Time to failure (i.e., moving out of position or opening the eyes) is measured for a maximum of 30 seconds for each of two attempts, and the longer of two measured durations is reported in seconds, with higher values meaning better outcomes. Values are measured with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/ treatment-mode, B=constant/placebo-mode, or C=no stimulation) and reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM5.1 (A,B,C): slope of change in treadmill dynamic visual acuity with increasing walking speed (LogMAR/mph), A participant's visual acuity is measured while standing still and then while walking on a treadmill at 0.5, 1, 1.5, 2, 2.5 and 3 miles per hour (mph). The slope with which visual acuity (in logarithm base 10 of the minimum angle resolved, logMAR) worsens as treadmill speed increases (in mph) is measured from a line fit to the data and reported in units of (logMAR/mph), with values ranging from 0 to -1 and less negative numbers meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/ treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM5.2 (A,B,C): maximum treadmill velocity achieved during (mph), A participant's visual acuity is measured while standing still and then while walking on a treadmill at 0.5, 1, 1.5, 2, 2.5 and 3 miles per hour (mph). The highest treadmill speed the participant tolerates is recorded in mph, with higher speeds meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM6.1 (A,B,C): gait speed when walking in well-light hall, A participant walks in a well-lit hall while gait speed is measured in m/s. Speeds range from 0-2 m/s, with higher values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM6.2 (A,B,C): gait speed when walking in dim light, A participant walks in dim light while gait speed is measured in m/s. Speeds range from 0-2 m/s, with higher values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM7.1 (A,B,C): TUG when walking in well-light hall, A participant performs the Timed Up and Go (TUG) test, which comprises rising from a chair, walking to and around a pylon, then returning to the chair and sitting, in a well-lit hall. Time to complete the TUG ranges over \~5-30 seconds, with lower values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM7.2 (A,B,C): TUG when walking in dim light, A participant performs the Timed Up and Go (TUG) test, which comprises rising from a chair, walking to and around a pylon, then returning to the chair and sitting, in dim light. Time to complete the TUG ranges over \~5-30 seconds, with lower values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM8.1 (A,B,C): gait speed when walking during dual task/cognitive distraction (Serial 7s downward counting), While counting downward in increments of -7 (from a number randomly selected between 91 and 109 by the examiner), a participant walks in a well-lit hall and gait speed is measured in m/s. Speeds range from 0-2 m/s, with higher values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM8.2 (A,B,C): TUG during dual task/cognitive distraction (Serial 7s), While counting downward in increments of -7 (from a number randomly selected between 91 and 109 by the examiner), a participant performs the Timed Up and Go (TUG) test, which comprises rising from a chair, walking to and around a pylon, then returning to the chair and sitting, in dim light. Time to complete the TUG ranges over \~5-30 seconds, with lower values meaning better outcome. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM9 (A,B,C): Serial 7s downward counting while standing with eyes open, A participant counts downward for 20 seconds in increments of -7 (from a number randomly selected between 91 and 109 by the examiner) while standing with eyes open. The number of increments correctly subtracted is counted, with higher number of increments meaning better performance. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM10.1 (A,B,C): time to complete the Trail Making Test Part B (TMT), A participant performs the Trail Making Test Part B (TMT), using a pen to connect a set of 25 pre-drawn and numbered circles on a sheet of paper as quickly as possible while being accurate. The time in seconds required to complete the test is recorded, with shorter time meaning better performance. The test is repeated with the study device providing three different modes of prosthetic stimulation (A=motion-modulated/treatment-mode, B=constant/placebo-mode, or C=no stimulation). Results are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM10.2 (A,B,C): performance on the Triangle Completion Test (TCT), After a practice trial with eyes open, a participant performs the Triangle Completion Test (TCT). The blindfolded participant is assisted while walking slowly along 2 segments of a pre-drawn 92.5 × 185.5 × 212 cm, 30°-60°-90° triangular path and instructed to complete the final segment independently, ending at his/her best estimate of the starting point. The participant walks counterclockwise for two triangles and then clockwise for two. End point is marked midway between each foot's largest toe. Distance (in cm, range \~0-100, smaller better) from end point to starting point and angle (absolute value, range 0-180 deg, smaller better) between the participant's path and the correct path are averaged over four trials. The test is repeated with the study device providing three modes of prosthetic stimulation: A (motion-modulated), B (constant rate) and C (off). Results are reported as a 3 by 2-valued matrix., 4 years post-implantation up to 5 years post-enrollment|XM11: electrode impedance, Electrical impedances are measured using 26.67 microsecond/phase biphasic current pulses at 302.4 cu (clinical units) of current for each of the 9 stimulating electrodes and reported as a 9-valued vector. Values range from 0 to 25 kiloohm (kΩ). Values of \<2 kΩ, abnormally low and values \>15 kΩ are abnormally high, values in the range 2-15 kΩ are normal, and values closer to normal range mean better outcome. Impedances for the 9 electrodes are reported as a 9-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM12: electrode location distance, as determined by post-implantation computed tomography (CT) imaging, For each canal, the distance between the center of crista ampullaris and the nearest stimulating electrode is measured on a post-implantation computed tomography (CT) scan in mm, with values ranging from 0-5 mm and smaller values meaning better outcome. Best-electrode distances for the 3 canals are reported as a 3-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM13: vestibular evoked compound action potential (veCAP)24 amplitude, Peak vestibular-evoked compound action potential (veCAP) amplitude is measured for each implanted electrode and reported for the 9 implanted electrodes, with range 0-1000 microvolts and higher values meaning better outcome, as a 9-valued vector., 4 years post-implantation up to 5 years post-enrollment|XM14.1: scalp thickness over the implant, measured on post-operative CT imaging, Scalp thickness over the implant is measured in mm using a post-operative CT scan performed 3 weeks after implantation., 4 years post-implantation up to 5 years post-enrollment|XM14.2: inductively-measured intercoil distance between implant antenna coil and external processor antenna coil, Inductively-measured intercoil distance between implant antenna coil and external processor antenna coil is measured in mm 3 weeks after implantation and 4 years post-implantation, and the change between those two values is reported in mm, with numbers less than (initial thickness minus 3 mm) meaning better outcome., 4 years post-implantation up to 5 years post-enrollment|XM15.1: Bilateral Vestibulopathy Questionnaire score (BVQ), The Bilateral Vestibulopathy Questionnaire English version (BVQ) is a 24-question survey intended to quantify patient-reported disease burden due to bilateral vestibular hypofunction. Each question is answered on a 6-item Likert scale, with scores for positively-worded questions reversed before scoring. After averaging scores within each of 4 construct subsets, the 4 construct values are added to yield overall BVQ score, ranging from 4 to 24. Higher score means worse outcome., 4 years post-implantation up to 5 years post-enrollment|XM15.2: Number of Audio/video recording of structured interviews, Audio and video recording of a participant's responses to a structure set of questions regarding symptoms of bilateral vestibular hypofunction will be made preoperatively and at 4 years postoperatively. Responses are free-format and not quantified. The number of participants who complete video/imaging will be reported., 4 years post-implantation up to 5 years post-enrollment|XM16: Vestibular Activities of Daily Living score (VADL), Vestibular Activities of Daily Living (VADL) is a survey designed to quantify self-rated disability due to vestibular dysfunction. Scores range from 1 (least disabled, best outcome) to 10 (worst outcome) points., 4 years post-implantation up to 5 years post-enrollment|XM17 (A,B,C): Oscillopsia Visual Analog Scale score (oVAS), The Oscillopsia Visual Analog Scale (oVAS) is a 43-question survey designed to quantify self-rated oscillopsia. Each item is answered on a 6-point Likert scale (integer scores of 0 to 5, with the score X for each negatively phrase questions transformed to 5-X before summation across all questions). Total score ranges from 0 (least oscillopsia, best outcome) to 215 (worst outcome) points., 4 years post-implantation up to 5 years post-enrollment|XM18: Activities-specific Balance Confidence Scale score (ABC), The Activities-specific Balance Confidence Scale (ABC) is a 16-question survey designed to quantify self-rated confidence performing daily activities that require balance. Each item is answered on an 11-item Likert scale (from 0 to 100% confidence, in 10% increments). Total score is the average of the 16 responses and ranges from 0 (least confident, worst outcome) to 100% (most confident, best outcome)., 4 years post-implantation up to 5 years post-enrollment|XM19.1: Vertigo Symptom Scale score (VSS), The vertigo-balance subscale score of the Vertigo Symptom Scale is a 15-item survey designed to quantify self-rated vertigo symptom severity. Each item is answered on a 5-item Likert scale (from 0 to 4, higher meaning more frequent/worse symptoms). Total score is the sum of the 15 responses and ranges from 0 (least severe/frequent, best outcome) to 75 (worst outcome)., 4 years post-implantation up to 5 years post-enrollment|XM19.2: Vertigo Visual Analogue Scale score (VAS), The Vertigo Visual Analogue Scale is a 9-item visual analogue scale designed to assess the intensity of vertigo symptoms for patients in different daily situations that typically induce visual vertigo. Each item is answered on a visual analogue scale by drawing a vertical line on a 10 cm line between two anchors marked 0 and 10 (with zero (0) representing no dizziness and ten (10) representing most dizziness). Total score is the sum of the 9 responses, divided by the number of answered items, and multiplied by 10. (ranges from 0 (least severe, best outcome) to 100 (most severe, worst outcome)., 4 years post-implantation up to 5 years post-enrollment|XM20.1: Health Utilities Index Mark 3 (HUI), The Health Utilities Index Mark 3 is an instrument designed to measure health status and health-related quality of life. HUI Mark 3 provides a utility score ranging from 0 (worst outcome) to 1 (best outcome)., 4 years post-implantation up to 5 years post-enrollment|XM20.2: EuroQol 5 Dimension (EQ-5D), The EuroQOL EQ5D is a 5-dimension (mobility, self-care, usual activities, pain/discomfort, anxiety depression) instrument developed to evaluate health-related quality of life. Each of the five dimensions includes five levels of severity going from 1-5 (no problems (1), slight problems (2), moderate problems (3), severe problems (4), unable to/extreme problems (5)). Scores for each dimension are combined to obtain a total score in the form of a 5 digit code (Greater number of higher scores means worse outcome.), 4 years post-implantation up to 5 years post-enrollment|XM21: Tinnitus Handicap Inventory (THI), The Tinnitus Handicap Inventory (THI) survey is set of questions designed to quantify self-perceived handicap due to tinnitus. THI score ranges from 0-100. Higher scores mean worse outcome., 4 years post-implantation up to 5 years post-enrollment|XM22: Autophony Index (AI), The Autophony Index (AI) survey is set of questions designed to quantify self-perceived autophony (hearing one's voice or other internally-generated body sounds). AI score ranges from 0-104. Higher scores mean worse outcomes., 4 years post-implantation up to 5 years post-enrollment|XM23.1: OTOSCOPE genetic testing panel (or equivalent panel from another Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory, such as Invitae Corpl) for participants who agree to genetic testing, For participants with a history of nonototoxic bilateral vestibular hypofunction who agree to clinical genetic testing, a University of Iowa Molecular Otology Research Laboratory OtoSCOPE® Genetic Hearing Loss Testing v9 test will be performed on a buccal swab to determine the presence or absence of an identifiably inner ear gene abnormality, and the deidentified result will be reported., Preoperative baseline|XM23.2: Presence or absence of Mitochondrially Encoded 12S RRNA (MTRNR1) gene abnormality as assessed by genetic test panel (or equivalent) for participants with known ototoxic exposure who agree to genetic testing, For participants with a history of ototoxic bilateral vestibular hypofunction who agree to clinical genetic testing, an MTRNR1 genetic testing panel screen will be completed to determine the presence or absence of an MTRNR1 gene abnormality, and the deidentified result will be reported., Preoperative baseline|XM23.3: RFC1 presence or absence of an MTRNR1 gene abnormality as assessed by Ataxia/CANVAS genetic testing panel (or equivalent) for participants suspected to have CANVAS or demonstrate potential CANVAS related symptoms, For participants with a history of ototoxic bilateral vestibular hypofunction who agree to clinical genetic testing, an MTRNR1 genetic testing panel screen will be completed to determine the presence or absence of an MTRNR1 gene abnormality, and the deidentified result will be reported., Preoperative baseline|XM24.1: Number of intraoperative video recordings of electrode implantation, Deidentified video of the implantation surgery will be recorded intraoperatively. The number of participants who complete intraoperative recording will be reported., Intraoperatively|XM24.2: Number of post-implantation temporal bone CT imagings, Deidentified images for a post-implantation temporal bone computed tomography (CT) scan will be recorded 3 weeks post-implantation. The number of participants who complete imaging will be reported., 3 weeks post-implantation|XM25: Study visit duration (days) by activity/test/assessment, Explore ways to improve efficiency of procedures for performance assessment and stimulus parameter adjustment by measuring change in study visit duration by activity/test/assessment., 4 years post-implantation up to 3 years post-enrollment|XM26: Number of audio/video recording of participants' descriptions of motion percepts during eeVOR testing, Deidentified audio/video of the of participants' descriptions of motion percepts during eeVOR testing. The number of participants who complete video/recording will be reported., 4 years post-implantation up to 3 years post-enrollment