Can Video Head Impulse Test Determine the Early Effect of Cochlear Implantation on the Semicircular Canals Function?

Background and Aim: Although cochlear implantation (CI) is a safe surgical procedure for severe to profound sensorineural hearing loss (SNHL) but, due to the embryological and anatomical connection between the vestibular and cochlear structures, vestibular dysfunction may occur after CI. Video head impulse test (vHIT) is a reliable test for assessing the function of semicircular canals (SCCs). This study aimed to determine the early effect of CI on SCCs function, by comparing pre- and post-operative vHIT results. Methods: In this cross-sectional study, participants were 22 adults with SNHL scheduled for unilateral CI in the right ear and 22 age-matched healthy subjects as a control group. The vHIT was conducted before and two weeks after CI. Results: The mean vHIT gains in the SNHL group were significantly lower than in controls, with a large effect size. Furthermore, the mean vHIT gains in the right lateral SCCs (p<0.001) and right anterior SCCs (p=0.003) were significantly reduced after CI, compared to the gain values before CI, with a large pooled effect size. However, these differences were not statistically significant for the right posterior SCCs. The comparison of vHIT gains in the nonimplanted ear showed no statistically significant difference between pre- and post-operative phases. Conclusion: The vHIT is a useful clinical method to detect the early effects of CI on the function of SCCs. These effects are more obvious in the lateral and superior SCCs in the implanted ear.