Otolith Assessment in CI Candidates and Patients with Cervical- and Ocular-Vestibular Evoked Myogenic Potentials (c/o-VEMPs)

Background

In contrast to semicircular canal assessment, the role of assessing otolith function in CI candidates and patients is not yet clear. Although cervical- and ocular- vestibular evoked myogenic potentials (c/o-VEMPs) get more attention nowadays, standardized c/o-VEMP measurement protocols are lacking. Otolith assessment might be useful in CI candidates/patients with residual hearing and residual vestibular function.

Objective

Investigating optimal measurement conditions (stimuli, scalp location, electrode configuration) for c/o-VEMPs for clinical implementation as an objective tool to evaluate pre- and postop otolithic function in CI.

Methods

c- and o-VEMP obtained by air- and bone-conducted stimuli respectively, are evaluated for different scalp locations. Stimuli consist of 250 to 1000 Hz tone bursts, presented via insert or a high-force level bone (HFL) conductor. Response amplitude, latency, reproducibility, inter-ocular ratio (IOR) and thresholds are determined, pre- and postoperatively.

Results

Significant differences are found for response amplitude, latency, reproducibility and IOR depend between c- and o-VEMPs. 500 Hz tone burst stimuli showed high reproducibility for c/o-VEMPs. o-VEMPs recordings were optimal with Fz stimulation and recording electrodes at belly-tendon of contralateral inferior oblique eye muscle in supine position, while for cVEMPs, sternocleidomastoideus referred to mastoids in upright sitting positions led to best responses. Data in CI subjects revealed that a substantial number of CI candidates already preoperatively show a loss of otolith function, therefore having a reduced risk of postop vestibular deterioration.

Conclusions

c/o-VEMP recordings are clinically useful to evaluate pre- and postop otolith function, particularly in CI patients with residual hearing and/or vestibular function.