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.
Adults older than 22 years old who
have previously been enrolled in Johns Hopkins University Institutional Review Board protocol NA_00051349, IRB00335294 or IRB00346924 and
have previously been implanted with a vestibular implant under FDA IDE G150198
None
Single group
Labyrinth Devices MVI™ Multichannel Vestibular Implant System
DeviceContinuously motion-modulated stimulation delivered by a vestibular implant already implanted under a prior study protocol (Labyrinth Devices MVI™ Multichannel Vestibular Implant System)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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Johns Hopkins University
Lead sponsor
National Institute on Aging (NIA)
Collaborator
National Institute on Deafness and Other Communication Disorders (NIDCD)
Collaborator
Labyrinth Devices, LLC
Collaborator
