Cochlear implantation and vestibular function in children

Objectives: To analyze vestibular function Q2 (VF) after cochlear implantation (CI) in children.

Methods: Retrospective cohort study at a tertiary pediatric referral center. 43 children that had vestibular testing (VT) after unilateral cochlear implantation, from 2001 to 2010, were included. CT scan of the temporal bone was done systematically before surgery. VT included three tests: head-impulse test, caloric tests, vestibular evoked myogenic potentials. VF was graded in: normal (type 1), partial dysfunction (type 2), severe dysfunction and areflexia (type 3). In 12 cases, VT was done before and after CI. Vestibular function was analyzed looking to side, etiology and preoperative status.

Results: Mean age at CI was 2.9 years. Bilateral inner ear malformation were retrieved in 16%. Before surgery, 50% of children had normal vestibular responses, 4/12 had bilateral type 2, two had asymmetrical VF. In this group, after surgery, 2 children had VF worsening, none on the CI side only. Considering all 43 patients, post operative VT showed normal response in 48.8% and type 2&3 in 16.2%. Children had asymmetrical poorer vestibular function on the side of CI in 19%. Among them, 75% had normal contralateral VF. Sensorineural hearing loss etiologies known to be associated with vestibulopathy (Usher/Meningitis/Inner Ear Malformations/CMV) were associated to abnormal vestibular function more frequently than in other causes (p=0.01).

Conclusion: Half of the children had initial vestibular dysfunction. In our study, 20% of cochlear implantation could have worsened vestibular function. As vestibular function should be part of the choice in cochlear implantation, side of implantation and survey; and vestibular tests are uneasy to achieve in pediatric population, we propose a three-steps evaluation and gradation which allow easier comparison.