Influence of electrical pulse shapes on vestibular evoked myogenic potentials when stimulated via cochlear implant electrodes

The spread of the electric current originating from the cochlear implant electrode can lead to an unintended co-stimulation of the otolith organs. This can be measured as electrical vestibular evoked myogenic potentials (eVEMPs), which can be measured as reflexes of the otolith organs on the neck and eye muscles in the electromyogram. It is unclear whether eVEMP has a positive or negative effect on the vestibular function. A prospective, experimental study is investigating whether the variation in the pulse shape of the electrical CI stimulus influences the eVEMP prevalence. In addition, the latencies, amplitudes and thresholds of the eVEMP are measured. CI users who showed eVEMP responses to monopolar and/ or bipolar stimulation with 4 pulses at 1000 Hz in a previous study were included in the study. Two biphasic electrical pulses at 500 Hz or 1000 Hz and a single pulse are used as stimuli. The stimulation amplitude was calibrated to the comfort level of the test subjects and the eVEMPs were recorded from the M. obliquus inferior and M. sternocleidomastoideus. The test subjects are also asked about their vertigo symptoms.

First results show that eVEMPs to stimulation with 2 pulses at 1000 Hz, 2 pulses at 500 Hz, and single pulses occur with a prevalence of 67 % . In some cases the eVEMP threshold is lower than the respective hearing threshold. Dizziness was evident in both subjects for whom eVEMPs could be elicited and subjects without eVEMPs.

The results show that the simultaneous stimulation of the otolith organs can also occur during everyday use of the CI. However, the first measurements show that the occurance of eVEMPs is independet of the pulse shape.

Poster-PDF A-1178.pdf

Publication History

Article published online:
13 May 2021