Vestibular impairments pre- and post-cochlear implant in children.

OBJECTIVES

Determine prevalence and types of vestibular impairments in sensorineural hearing loss (SNHL) in a large population of pediatric candidates for cochlear implants. Evaluate impact of cochlear implants on vestibular function.

STUDY DESIGN

Retrospective and prospective study.

METHODS

Children with profound SNHL (n=224) underwent complete vestibular testing (clinical vestibular examination, bicaloric test, earth vertical axis rotation, off vertical axis rotation and vestibular evoked myogenic potentials) before cochlear implant. Changes in vestibular responses were measured after implants in 89 of these patients.

RESULTS

In the SNHL population only 50% had normal bilateral vestibular function, while 20% had bilateral complete areflexia, 22.5% partial asymmetrical hypoexcitability and 7.5% partial symmetrical hypoexcitability. In the 71/89 follow-up patients showing vestibular responses prior to implant, 51 (71%) had changes in vestibular function including 7 (10%) who acquired ipsilateral areflexia. Others developed ipsilateral hypo- or hyperexcitability. Vestibular modifications occurred during the 3 months after surgery and were not clearly associated with clinical signs except for ipsilateral areflexia cases. In long-term follow-up, two of the 7 patients with ipsilateral areflexia partially recovered vestibular function.

CONCLUSION

Since half of pediatric cochlear implant candidates have vestibular deficits and 51% of implants induce modifications of existing vestibular function, each implant should be preceded by canal and otolith functional tests to assure that the least functional vestibule is implanted. The tests provide baselines for follow-up monitoring of subsequent losses and recovery. This could be easily implemented with a clinical vestibular examination including the head thrust test associated with a bicaloric test and vestibular-evoked-myogenic-potentials.