Implantation of the Semicircular Canals With Preservation of Hearing and Rotational Sensitivity

Abstract

Hypothesis It is possible to implant a stimulating electrode array in the semicircular canals without damaging rotational sensitivity or hearing. The electrodes will evoke robust and precisely controlled eye-movements Background A number of groups are attempting to develop a neural prosthesis to ameliorate abnormal vestibular function. Animal studies demonstrate that electrodes near the canal ampullae can produce electrically-evoked eye movements. The target condition of these studies is typically bilateral vestibular hypofunction. Such a device could potentially be more widely useful clinically, and would have a simpler roadmap to regulatory approval if it produced minimal or no damage to the native vestibular and auditory systems. Methods An electrode array was designed for insertion into the bony semicircular canal adjacent to the membranous canal. It was designed to be sufficiently narrow so as to not compress the membranous canal. The arrays were manufactured by Cochlear Ltd and linked to a Nucleus Freedom receiver/stimulator. Seven behaviorally-trained rhesus macaques had arrays placed in two semicircular canals using a transmastoid approach and “soft-surgical” procedures borrowed from Hybrid cochlear implant surgery. Postoperative vestibulo-ocular reflex was measured in a rotary chair. Click-evoked auditory brainstem responses were also measured in the seven animals using the contralateral ear as a control. Results All animals had minimal postoperative vestibular signs and were eating within hours of surgery. Six out of six animals tested had normal postoperative sinusoidal gain. Six out of seven animals had symmetric postoperative velocity-step responses toward and away from the implanted ear. The one animal with significantly asymmetric velocity-step responses also had a significant sensorineural hearing loss. One control animal which underwent canal-plugging had substantial loss of the velocity-step response toward the canal-plugged ear. In five animals, intraoperative electrically-evoked vestibular compound action potential (ECAP) recordings facilitated electrode placement. Postoperatively, electrically evoked eye-movements were obtained from electrodes associated with an ECAP waveform. Hearing was largely preserved in six animals and lost in one animal. Conclusions It is possible to implant the vestibular system with prosthetic stimulating electrodes without loss of rotational sensitivity or hearing. Since electrically-evoked eye-movements can be reliably obtained with the assistance of intraoperative electrophysiology, it is appropriate to consider treatment of a variety of vestibular disorders using prosthetic electrical stimulation. Based on these findings, and others, a feasibility study for the treatment of human subjects with disabling Meniere’s disease has begun.

Loss of Afferent Vestibular Input Produces Central Adaptation and Increased Gain of Vestibular Prosthetic Stimulation

“…Previous studies (e.g., Rubinstein et al 2012) demonstrated that natural vestibular rotational sensitivity could be preserved in the short term following implantation of a vestibular neurostimulator in monkeys when the electrode placement and design maintained the patency of the lumen of the implanted semicircular canal. This finding was not replicated in human subjects with a diseased ear prior to implantation Golub et al 2014).…”

“…Implantable, single-and multi-channel vestibular neurostimulators, which deliver trains of biphasic pulses to afferents of individual branches of the ampullar nerves innervating the three semicircular canals, have been extensively studied in animal models, particularly non-human primates, using devices developed by several groups (Davidovics et al 2011;Della Santina et al 2005Gong et al 2008;Dai et al 2011a, b;Lewis et al 2001Lewis et al , 2002Lewis et al , 2010Nie et al 2013;Phillips et al 2011Phillips et al , 2012Phillips et al , 2015bRubinstein et al 2012). This type of electrical stimulation has long been known to modulate the behavior of vestibular afferents (Goldberg et al 1984) and to elicit eye movements Cohen and Suzuki 1963;Suzuki and Cohen 1964) comparable to those produced by the angular vestibulo-ocular reflex (aVOR).…”

Multichannel Vestibular Prosthesis Employing Modulation of Pulse Rate and Current with Alignment Precompensation Elicits Improved VOR Performance in Monkeys

“…By delivering biphasic, symmetric, charge-balanced, rate-modulated pulses, the device generated partly compensatory eye movements for head rotations about the gyro's axis of rotational sensitivity. Wall, Guyot, and colleagues have applied a similar approach to single-channel vestibular nerve stimulation in humans (Wall et al 2007;Guyot et al 2011aGuyot et al , b, 2012, and Nie, Phillips, Rubinstein, and colleagues have recently applied analogous technology to monkeys and a human subject as part of an effort to develop a vestibular pacing device for treatment of Ménière's disease (Nie et al 2011;Rubinstein et al 2012).…”

Vestibuler rehabilitation in bilateral vestibulopaty

“…Şimdiki çalışmalar VOR in oluşturulması için uygun elektik stimulasuyon modelini bulmak ve VOR' deki adaptif mekanizmaları geliştirmek üzerine odaklanmıştır (56). Kulakta bulunan saç hücrelerinin yenilenmesini teşvik etmek için geliştirilen vestibuler protezler, genetik olarak gentamisin duyarlılığnın tespiti, kulaktaki saçlı hücre kaybı için alfa lipoik asit coenzyme Q10 gibi anti oksidan kullanımı gündemde olan tedavilerdir (57,58).…”