Electrical Vestibular Stimulation in Humans: A Narrative Review

Abstract

Background: In patients with bilateral vestibulopathy, the regular treatment options, such as medication, surgery, and/or vestibular rehabilitation, do not always suffice. Therefore, the focus in this field of vestibular research shifted to electrical vestibular stimulation (EVS) and the development of a system capable of artificially restoring the vestibular function. Key Message: Currently, three approaches are being investigated: vestibular co-stimulation with a cochlear implant (CI), EVS with a vestibular implant (VI), and galvanic vestibular stimulation (GVS). All three applications show promising results but due to conceptual differences and the experimental state, a consensus on which application is the most ideal for which type of patient is still missing. Summary: Vestibular co-stimulation with a CI is based on “spread of excitation,” which is a phenomenon that occurs when the currents from the CI spread to the surrounding structures and stimulate them. It has been shown that CI activation can indeed result in stimulation of the vestibular structures. Therefore, the question was raised whether vestibular co-stimulation can be functionally used in patients with bilateral vestibulopathy. A more direct vestibular stimulation method can be accomplished by implantation and activation of a VI. The concept of the VI is based on the technology and principles of the CI. Different VI prototypes are currently being evaluated regarding feasibility and functionality. So far, all of them were capable of activating different types of vestibular reflexes. A third stimulation method is GVS, which requires the use of surface electrodes instead of an implanted electrode array. However, as the currents are sent through the skull from one mastoid to the other, GVS is rather unspecific. It should be mentioned though, that the reported spread of excitation in both CI and VI use also seems to induce a more unspecific stimulation. Although all three applications of EVS were shown to be effective, it has yet to be defined which option is more desirable based on applicability and efficiency. It is possible and even likely that there is a place for all three approaches, given the diversity of the patient population who serves to gain from such technologies.

Bilateral vestibulopathy: beyond imbalance and oscillopsia

“…Taking these factors into account, it might be hypothesized that questionnaires like the DHI and HADS do not give an accurate view of symptoms and their consequences in (at least) BV patients [32]. Therefore, it is important to take this into consideration during the development of candidacy criteria and outcome measures for therapeutic interventions such as the vestibular implant, balance belt, noise galvanic vestibular stimulation and rehabilitation [4,[19][20][21][22][23][24][60][61][62][63]. It should be considered to develop a BV-specific patient-reported outcome measure (PROM) [27,64] which takes all the relevant symptoms and adaptation to symptoms into account.…”

“…However, it does not restore the function. Research on galvanic vestibular stimulation which uses surface electrodes shows some promising results regarding improvement of balance and gait [18][19][20]. The vestibular implant is another possible treatment option for the future.…”

Differences in Vestibular-Evoked Myogenic Potential Responses by Using Cochlear Implant and Otolith Organ Direct Stimulation

“…As previously described, vestibular costimulation may help to restore damaged vestibular function (17,32) but may not be considered for all situations in cochlear implant recipients TABLE 6 | An example of VOR gain in six canals (VHIT) before and after cochlear implant group (example of C1 patient).…”

Seltene Erkrankungen des vestibulären Labyrinths: von Zebras, Chamäleons und Wölfen im Schafspelz

“…Eine Wiederherstellung verloren gegangener peripher-vestibulärer Funktion ist nach aktuellem Stand der Forschung nur durch ein vestibuläres Implantat möglich. In Analogie zum Cochlea-Implantat werden hier Drehbeschleunigungen des Kopfes durch ein extern am Kopf getragenes Gyroskop detektiert und vom Implantat in ein elektrisches Signal umgewandelt, welches über Elektroden die entsprechenden Äste des N. vestibularis stimuliert [365][366][367][368][369][370].…”