14Hearing and Balance Together: The Combined Cochleovestibular Implant

FThe central trade-off: balance gain at hearing's expense

Semicircular-canal electrodes are placed within millimetres of the cochlea; opening the labyrinth and passing current near it can reduce or abolish cochlear hearing in the implanted ear. In the Johns Hopkins trial, the air-conducted pure-tone average worsened by 3-16 dB in some recipients but by 74-104 dB in others — effectively losing usable hearing in that ear. Hearing loss is therefore a recognised and sometimes severe risk of stand-alone vestibular implantation, not a rare complication. A landmark case showed that intralabyrinthine electrode insertion need NOT acutely abolish cochlear function (ABR-monitored), proving hearing preservation is at least sometimes achievable — but it cannot yet be guaranteed.[2021][2017]

CReframing the cost: when hearing is already lost

The trade-off changes character when the candidate has already lost hearing in the target ear — then there is no hearing to sacrifice, only balance to gain. Classic combined-candidate scenarios are bilateral Meniere's disease and aminoglycoside (e.g. gentamicin) ototoxicity, where the same insult destroys both cochlear and vestibular function. In these patients a single device that restores hearing AND balance is far more attractive than a vestibular-only implant that leaves a deaf, balance-implanted ear. This reframing turns the cochleovestibular implant from a compromise into a logical, organ-matched solution for combined audiovestibular loss.[2021][2025]

TOne device for two organs

A combined cochleovestibular implant carries a conventional cochlear electrode array for the scala tympani plus additional electrodes targeting the semicircular-canal and otolith nerves. A pilot cochleovestibular series reported pure-tone average improving from about 78 dB HL preoperatively to roughly 34-36 dB HL with the device on, alongside balance gains. The same study added otolith (gravity/linear-acceleration) stimulation, broadening the restored signal beyond the rotation-sensing canals toward a more complete vestibular percept. Sensory Organization Test scores rose from about 33% to 68% and gait improved, with some residual balance benefit persisting briefly after the device was switched off — a sign of central adaptation.[2025][2017]

TChoosing the right candidate

Candidate selection balances the value of any residual hearing in the ear against the potential balance gain — the more hearing left to lose, the higher the bar. Ideal combined candidates have profound or absent hearing plus disabling bilateral vestibular loss in the same ear, so the device only adds function. Where useful residual hearing exists, hearing-preservation surgical technique and electrode design become decisive, and a vestibular-only or watchful approach may be preferred. Because both functions are restored in one operation, the combined device also spares the patient a second surgery and a second implanted ear.[2017][2025]