Influence of the ground path on vestibular evoked myogenic potentials with electrical stimulation via a cochlear implant

The recording of vestibular evoked myogenic potentials (VEMP) evoked by acute or vibratory stimulation is used to measure otolith function. VEMPs can also be evoked by electrical stimulation via a cochlear implant (CI) (eVEMP). We postulate that this interfering vestibular co-excitation occurs due to a diffuse spread of electric current additionally to the precise intracochlear spiral ganglia stimulation.

In a prospective study on 30 Nucleus CI users with a CP910 audio processor, the prevalence, amplitudes, thresholds and latencies of these electrical VEMPs (eVEMP) are measured depending on the path of electrical stimulation and correlated with the transimpedance matrix. The electrical ground path is varied between monopolar and bipolar modes. The eABR module of the Custom Sound EP software (Cochlear) is used for stimulation.

First results show that the mean latencies of the cervical eVEMPs were 11.6ms (P₁) and 22.2ms (N₁), those of the ocular eVEMPs 10.7ms (N₁) and 15.0ms (P₁). Monopolar stimulation of electrode E3 evoked eVEMPs in 27 %  of the patients, bipolar stimulation of electrodes E3 and E14 in 18 % . In the use of monopolar stimulation of electrode E20, no eVEMPs were evoked. The mean threshold was at a current level of 190. Also, suprathreshold electrical stimulation could evoke eVEMP responses.

The results show that by varying the ground path, vestibular co-excitation caused by the CI can be reduced. This could be important for the CI fitting for everyday use. The question whether a co-excitation results in harm or benefit in everyday life for the CI patients is still open.

Poster-PDF A-1177.pdf

Publication History

Article published online:
13 May 2021