Restoring the Sixth Sense in 3D: The Johns Hopkins MVP
Bilateral loss of vestibular function (inner ear balance sensation) due to ototoxic hair cell injury is disabling, with patients suffering disequilibrium and inability to maintain stable vision during head movements typical of daily life. While most individuals with partial loss compensate through rehabilitative strategies enlisting other senses, those who fail to compensate for profound loss have no good therapeutic options. Because the vestibular nerve should be intact in many of these patients, electrical stimuli encoding head rotation should be able to drive the nerve and restore sensation of head movement, much like a cochlear implant restores auditory function.
Vestibular prosthesis/implant research in the Johns Hopkins Vestibular NeuroEngineering Laboratory is guided by two broad goals. The first is to advance development toward an implantable neuroelectronic prosthesis that restores function to people disabled by bilateral loss of vestibular sensation. The second is to advance understanding of how the vestibular system encodes and responds to head motion, and how the system learns to adjust to changes in inner ear function, injury, age, genetic mutations and changes in visual context (like switching between glasses and contact lenses). We do this through basic neuroscience research and through engineering new technologies that enable neuroscientists to study the vestibular system in ways that would otherwise be impossible.
This project builds upon significant progress we have already made toward this goal, including: (1) development of a multichannel, head-mounted prosthesis able to encode three-dimensional (3D) head rotation via electrical stimulation of three or more vestibular nerve branches; (2) characterization of the 3D angular vestibulo-ocular reflex (VOR), vestibular nerve activity and endorgan histology in animals after vestibular ototoxic injury due to gentamicin treatment; and (3) partial restoration of the 3D VOR via prosthetic stimulation.
Through extrapolation of electrode designs, stimulus optimization protocols, and surgical techniques from rodents to nonhuman primates to human, this project set the stage for the first-in-human clinical trial of a new vestibular implant intended to aid individuals disabled by loss of vestibular sensation.
For a list of papers the VNEL team has produced on this topic, click here.