RESUMEN
BACKGROUNDBilateral loss of vestibular (inner ear inertial) sensation causes chronically blurred vision during head movement, postural instability, and increased fall risk. Individuals who fail to compensate despite rehabilitation therapy have no adequate treatment options. Analogous to hearing restoration via cochlear implants, prosthetic electrical stimulation of vestibular nerve branches to encode head motion has garnered interest as a potential treatment, but prior studies in humans have not included continuous long-term stimulation or 3D binocular vestibulo-ocular reflex (VOR) oculography, without which one cannot determine whether an implant selectively stimulates the implanted ear's 3 semicircular canals.METHODSWe report binocular 3D VOR responses of 4 human subjects with ototoxic bilateral vestibular loss unilaterally implanted with a Labyrinth Devices Multichannel Vestibular Implant System vestibular implant, which provides continuous, long-term, motion-modulated prosthetic stimulation via electrodes in 3 semicircular canals.RESULTSInitiation of prosthetic stimulation evoked nystagmus that decayed within 30 minutes. Stimulation targeting 1 canal produced 3D VOR responses approximately aligned with that canal's anatomic axis. Targeting multiple canals yielded responses aligned with a vector sum of individual responses. Over 350-812 days of continuous 24 h/d use, modulated electrical stimulation produced stable VOR responses that grew with stimulus intensity and aligned approximately with any specified 3D head rotation axis.CONCLUSIONThese results demonstrate that a vestibular implant can selectively, continuously, and chronically provide artificial sensory input to all 3 implanted semicircular canals in individuals disabled by bilateral vestibular loss, driving reflexive VOR eye movements that approximately align in 3D with the head motion axis encoded by the implant.TRIAL REGISTRATIONClinicalTrials.gov: NCT02725463.FUNDINGNIH/National Institute on Deafness and Other Communication Disorders: R01DC013536 and 2T32DC000023; Labyrinth Devices, LLC; and Med-El GmbH.
Asunto(s)
Vestibulopatía Bilateral , Estimulación Eléctrica/instrumentación , Prótesis Neurales , Reflejo Vestibuloocular/fisiología , Vestíbulo del Laberinto , Vestibulopatía Bilateral/fisiopatología , Vestibulopatía Bilateral/cirugía , Humanos , Ototoxicidad/fisiopatología , Ototoxicidad/cirugía , Diseño de Prótesis , Vestíbulo del Laberinto/fisiopatología , Vestíbulo del Laberinto/cirugíaRESUMEN
The bone-anchored-hearing-aid (BAHA) transduces airborne sound into skull vibration. Current bilateral BAHA configurations, for sounds directly facing listeners, will apply forces that are in-phase with each other and directed roughly towards the center of the head. Below approximately 1000 Hz the two cochleae respond in approximately the same direction and with approximately the same phase to each BAHA, thus it may be preferable to drive bilateral BAHAs such that when one pushes, the other pulls. This can be achieved by adjusting the relative phase offset of the BAHAs, and doing so results in greater vibration and improved hearing threshold. In this paper we compare performance of bilateral BAHAs driven in this configuration to the standard configuration. In twelve normal participants we show significant improvements in low-frequency (≤750 Hz) hearing thresholds using out-of-phase BAHAs. The threshold measurements are further supported by velocimetric measurements taken at the cochlear promontory in a cadaveric head. Comparing vibration arising from each configuration confirms that out-of-phase driving results in greater vibration. Neither dataset shows either improved or reduced threshold at high frequencies.
Asunto(s)
Umbral Auditivo , Conducción Ósea , Cóclea/fisiología , Audífonos , Adulto , Audiometría , Cadáver , Diseño de Equipo , Femenino , Humanos , Flujometría por Láser-Doppler , Masculino , Persona de Mediana Edad , Transductores , VibraciónRESUMEN
Adaptation to visual motion can induce marked distortions of the perceived spatial location of subsequently viewed stationary objects. These positional shifts are direction specific and exhibit tuning for the speed of the adapting stimulus. In this study, we sought to establish whether comparable motion-induced distortions of space can be induced in the auditory domain. Using individually measured head related transfer functions (HRTFs) we created auditory stimuli that moved either leftward or rightward in the horizontal plane. Participants adapted to unidirectional auditory motion presented at a range of speeds and then judged the spatial location of a brief stationary test stimulus. All participants displayed direction-dependent and speed-tuned shifts in perceived auditory position relative to a 'no adaptation' baseline measure. To permit direct comparison between effects in different sensory domains, measurements of visual motion-induced distortions of perceived position were also made using stimuli equated in positional sensitivity for each participant. Both the overall magnitude of the observed positional shifts, and the nature of their tuning with respect to adaptor speed were similar in each case. A third experiment was carried out where participants adapted to visual motion prior to making auditory position judgements. Similar to the previous experiments, shifts in the direction opposite to that of the adapting motion were observed. These results add to a growing body of evidence suggesting that the neural mechanisms that encode visual and auditory motion are more similar than previously thought.