Vestibular Function in Children and Adults Before and After Unilateral or Sequential Bilateral Cochlear Implantation

Abstract

Background: Cochlear implantation (CI) helps patients with severe or profound sensorineural hearing loss (SNHL) restore hearing and speech abilities. However, some patients exhibit abnormal vestibular functions with symptoms such as dizziness or balance disorders, after CI. Whether age at CI and CI approach (unilateral or sequential bilateral) affect vestibular functions in users with cochlear implants remains unclear. Objectives: To investigate the vestibular functions in children and adults before and after unilateral or sequential bilateral CI. Materials and Methods: Thirty-seven patients with severe or profound SNHL who were candidates for a first- or second-side CI were divided into three groups: first-side CI-implanted adults (≥18 years), first-side CI-implanted children (6-17 years), and second-side CI-implanted children (6-17 years). All cases were implanted with the round window approach to minimize damage to the intra-cochlear structures. The caloric test, vestibular evoked myogenic potential (VEMP) test, video head impulse test (vHIT), Dizziness Handicap Inventory (DHI), Pediatric Vestibular Symptom Questionnaire (PVSQ), and audiometric tests were performed before and 1 month after CI. Results: The abnormal rates of caloric test and VEMP test after CI in the first-side CI-implanted adults and children significantly increased compared with those before CI. The pre-implantation VEMP test showed significantly higher abnormal rates between first- and second-side CI-implanted children. No other significant differences of abnormal rates between first- and second-side CI-implanted children or between first-side CI-implanted adults and children were found. In second-side CI-implanted children, PVSQ scores significantly increased at day 3 post-implantation but decreased at day 30. Conclusion: CI has a negative effect on the results of caloric and VEMP tests, but not on vHIT, indicating that the otolith and low-frequency semicircular canal (SCC) are more vulnerable to damage from CI. The alterations of vestibular functions resulting from CI surgery may be independent of age at CI and CI approach (unilateral or sequential bilateral). Long-term impacts on the vestibular function from CI surgery, as well as the chronic electrical stimulation to the cochlea, are still to be investigated.

Keywords: adults; children; cochlear implant; sequential bilateral implantation; unilateral implantation; vestibular function.

Figure 1

Abnormal rates of vestibular functions revealed by the caloric test, vestibular evoked myogenic potential (VEMP) test and video head impulse test (vHIT) before and after cochlear implantation (CI). The abnormal rates significantly increased from pre- to post-implantation in (A) first-side CI-implanted adults and (B) first-side CI-implanted children, as revealed by the caloric test, ocular VEMP (oVEMP) and cervical VEMP (cVEMP). The pre- and post-implantation abnormal rates of functions of horizontal canal (HC), anterior canal (AC) and posterior canal (PC) in vHIT were not significantly different. (C) No significant difference of the abnormal rates was found between pre- and post-implantation tests in the second-side CI-implanted children. *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 2

Ratio of patients with abnormal vestibular functions revealed by pre- and post-implantation caloric test, VEMP test, and vHIT in first-side CI-implanted adults and children. (A) Pre- and (B) post-implantation tests showed no significant difference of abnormal rates between first-side CI-implanted adults and children.

Figure 3

Growth rates of abnormal vestibular functions revealed by the caloric test, VEMP test and vHIT. No significant difference of growth rates was found (A) between first-side CI-implanted adults and children or (B) between first- and second-side CI-implanted children.

Figure 4

Ratio of patients with abnormal vestibular functions revealed by pre- and post-implantation caloric test, VEMP test and vHIT in first- and second-side CI-implanted children. (A) Higher abnormal rates for pre-implantation oVEMP and cVEMP were found in first-side CI-implanted children than in second-side CI-implanted children. (B) Post-implantation tests showed no significant difference of abnormal rates between these two groups. *p < 0.05, **p < 0.01.