Development of a Multichannel Vestibular Prosthesis Prototype by Modification of a Commercially Available Cochlear Implant

Abstract

No adequate treatment exists for individuals who remain disabled by bilateral loss of vestibular (inner ear inertial) sensation despite rehabilitation. We have restored vestibular reflexes using lab-built multichannel vestibular prostheses (MVPs) in animals, but translation to clinical practice may be best accomplished by modification of a commercially available cochlear implant (CI). We developed software and circuitry to sense head rotation and drive a CI's implanted stimulator (IS) to deliver up to 1Kpulses/s via 9 electrodes implanted near vestibular nerve branches. Studies in two rhesus monkeys using the modified CI (MCI) revealed in vivo performance similar to our existing dedicated MVPs. Like commercially available CIs, our design uses an external head-worn unit (HWU) that is magnetically coupled across the scalp to the IS. The HWU must remain securely fixed to the skull to faithfully sense head motion with gyroscopes and maintain continuous stimulation. We measured normal and shear force thresholds at which HWU-IS decoupling occurred as a function of scalp thickness and calculated pressure exerted on the scalp. The HWU remained attached across the human scalp thicknesses from 3mm to 7.8mm for forces experienced during routine daily activities, with magnets exerting pressure on the scalp that remains below capillary perfusion pressure.

Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation

“…Identifying the more effective modulation paradigm has become increasingly relevant, as the concept of using modified cochlear implants has shown promise (Guyot et al 2011a(Guyot et al , 2011b and is being adopted also by other groups (Valentin et al 2013, Golub et al 2014, Phillips et al 2015. Cochlear implants use PAM per default for speech encoding.…”

“…Electrode placement and design could be adapted to specifically target remaining intact neurons in the ampullae, along the course of the vestibular nerve branches or Scarpa's ganglion to better address the patient's specific vestibular pathology (Van De Berg et al 2012, Guinand et al 2015). Furthermore, a multisite electrode array with a forked design (Valentin et al 2013) or a double-sided design (Poppendieck et al 2014) would facilitate fine-tuning of stimulation through multipolar stimulation, similar to investigations in cochlear implants (Bonham and Litvak 2008). These refinements will have to be evaluated as they could change the recruitment of primary afferents and improve the responses to PRM and, or PAM.…”

“…A systematic comparison of PAM and PRM has recently become increasingly necessary and urgent with the more widespread adoption of modified cochlear implants for vestibular stimulation (Valentin et al 2013, Golub et al 2014, Guinand et al 2015. The study herein is the first systematic comparison of both modulation paradigms in patients.…”

Neurocognitive factors in sensory restoration of early deafness: a connectome model

“…Cochlear implants, which are used to treat severe to profound sensorineural hearing loss, have become the most successful neuroprosthetic device, with more than 350 000 recipients worldwide. 2 Retinal and vestibular implants have also been developed and, although showing considerable promise, 3,4 their clinical success has not yet reached the level of cochlear implants. Sensory impairments not only frequently accompany other neurological diseases but also result in neurocognitive impairments.…”

Vestibular Implants: 8 Years of Experience with Electrical Stimulation of the Vestibular Nerve in 11 Patients with Bilateral Vestibular Loss

“…Devices with single- or multichannel independent vestibular arrays have been designed and/or manufactured [9,10,11,12,13]. Different motion sensor fixation and signal processing strategies have been proposed, leading to the recent filing of several patents [14,15,16,17,18].…”