Long-term results of hearing preservation cochlear implant surgery in patients with residual low frequency hearing

Abstract

Conclusion: Differences were found between patients with stable hearing and those with progressive hearing loss in the lower frequencies with respect to the rate of progression in the contralateral ear. It is suggested that the electric acoustic stimulation (EAS) can provide improvement in hearing ability over the long-term if residual hearing might be lost to some extent.

Objective: To evaluate the long-term threshold changes in the low frequency hearing of the implanted ear as compared with the non-implanted ear, and the hearing abilities with EAS along with the extent of residual hearing.

Methods: Seventeen individuals were enrolled and received the EAS implant with a 24-mm FLEXeas electrode array. Hearing thresholds and speech perception were measured pre- and post-operatively for 1–5 years. Post-operative hearing preservation (HP) rates were calculated using the preservation numerical scale.

Results: The average linear regression coefficient for the decline in hearing preservation score was −6.9 for the implanted ear and the patients were subsequently categorized into two groups: those with better than average, stable hearing; and those with worse than average, progressive hearing loss. EAS showed better results than electric stimulation alone, in spite of an absence of speech perception with acoustic stimulation.

Keywords:

• Cochlear implant
• electric acoustic stimulation
• hearing loss
• speech perception

Disclosure statement

MED-EL supplied EAS systems including implants and speech processors for this clinical trial as this cochlear implant system had not yet been approved by the Ministry of Health of Japan in 2009. The authors disclosed the above conflict of interest in this clinical research to the Ethics Committee of Shinshu University School of Medicine and received the Committee?s approval.

Funding

This study was supported by a Health and Labour Sciences Research Grant for Comprehensive Research on Disability Health and Welfare from the Ministry of Health, Labour and Welfare of Japan (S.U.), and by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (S.U.).