Vestibular dysfunctions in cochlear implant patients; A vestibular evoked myogenic potential study

Vestibular evoked myogenic potential in response to click or short tone burst stimuli have been used as a clinical test for distinguish saccule and inferior vestibular nerve diseases. Different studies show that cochlear implant could have inverse effects on vestibular structures. We aimed to investigate vestibular evoked myogenic potential in unilateral cochlear implanted individuals in compare to normal individuals. Thirty-three unilateral cochlear implanted patients (mean age 19.96 years) and 30 normal hearing individuals (mean age 24-27 years) as control group were enrolled in this cross- sectional study. Absolute latencies and amplitudes of myogenic potential responses were measured and compared in both groups. Myogenic potential recorded in both ears of all controls were normal. No response could be recorded in 16 patients (48.48%) from both ears. In three patients, responses were recorded in both ears though the amplitude of waves was reduced in implanted ear. Unilateral response could be recorded in 14 patients only in their non-implanted ear. Vestibular evoked myogenic potential test is a useful tool for assessing saccular function in cochlear implant patients. Damages of osseous spiral lamina and basilar membrane after cochlear implantation could result in dysfunctions of vestibular organs specially saccule. It seems that saccule could be easily damaged after cochlear implantation. This would cause absence or reduced amplitudes in myogenic potential.