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
