Vestibular stimulation by multichannel cochlear implants.

The recipient of a Nucleus 22 multichannel cochlear implant began to experience severe vestibular stimulation related to the implant. This patient's experience initiated a study with the objective of determining the frequency of implant-related vestibulo-ocular stimulation. Subjects consisted of 17 randomly selected patients who use cochlear implants. Included in the study were 14 Nucleus 22 and three Med-El Combi 40-devices. Stimulation of the implants was performed both by individual channel and with sound field broad-band 80-dB noise using the users' normal device settings. Eye movements were monitored with infrared videonystagmography. Only one subject, who used a Med-El Combi 40, showed a consistent and strong ocular response to cochlear stimulation but had no subjective symptoms. The authors conclude that vestibulo-ocular activation is possible with multichannel cochlear implants but is infrequent and may not be clinically significant.