Vestibular Implant Imaging

Abstract

Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51-66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n ¼ 2) or flat panel CT (n ¼ 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9°(range, À57.5°to 45°), and the median reference electrode insertion length was 42 mm (range, À21À66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.

A prosthesis utilizing natural vestibular encoding strategies improves sensorimotor performance in monkeys

“…One factor that could contribute to such gain variability is differences in the precise placement of the electrodes targeting the ampullae [ 52 ]. Indeed, optimization of electrode placement is a focus of ongoing research [ 53 , 54 ]. In this context, our finding that biomimetic mappings enhance performance despite gain differences across subjects directly advocates for incorporating such coding strategies in clinical practice.…”

Vestibular Implant Surgery

“…2,3 The ideal reference electrode location remains uncertain. After inserting the reference electrode in the common crus via a fourth labyrinthotomy for the first seven cases, 5 we have since converted to putting it in a subperiosteal pocket, under the temporalis muscle posteriorly or near the receiver/stimulator. Further, wrapping the reference electrode in a piece of fascia may help elevate it off the bone, thereby reducing both its impedance and the likelihood of exciting neighboring sensory neurons.…”

Prosthetic Stimulation of the Vestibular Nerve Can Evoke Robust Eye and Head Movements Despite Prior Labyrinthectomy

“…Post-labyrinthectomy, preimplantation CT imaging was not available for this case. It could have provided helpful surgical guidance (e.g., showing whether remnants of the medial ampulla walls are still present) and information the extent of tissue removal during labyrinthectomy (18). Although preoperative imaging is not normally needed to identify ampullae in an ear with normal anatomy, presurgical imaging to aid in surgical planning would likely increase the success rate of postlabyrinthectomy electrode implantation.…”