Results of Hearing Preservation Technique in Cochlear Implants
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- Category: Vol. 77, June 2009
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Results of Hearing Preservation Technique in Cochlear Implants,MONDY HAMMAD
Abstract
Introduction: Residual hearing preservation in cochlear implantation through soft surgery was first described in 1993. The technique didn’t gain wide acceptance because the advan-tages of residual hearing in cochlear implants candidates were questionable. In 1999, the positive effect of combined electric acoustic stimulation (EAS) of the auditory nerve on speech discrimination was first demonstrated and confirmed later in many publications. Higher rate of hearing preservation becomes possible through maturation of the soft surgery technique.
Aim of Work: To find different factors that can affect the preservation of residual hearing in cochlear implant surgery and combined EAS.
Material and Methods: This study was carried out in Kasr Al-Aini Cairo University Hospital and Mafraq Hospital, Abu Dhabi, UAE where eight cochlear implants patients with residual hearing in the low frequencies were operated using the soft surgery technique aiming at preservation of their residual hearing. Patients with preserved postoperative hearing were subjected to EAS through simultaneous use of hearing aid and cochlear implants. Factors that can affect hearing preservation were determined. The results of combined electric acoustic hearing were also analyzed.
Results: Hearing could be preserved either partially or completely in 5 out of 8 patients (62.5%). Factors that were found to affect the outcome of hearing are site of cochleostomy, the local use of dexamethasone and the depth of electrode insertion. Combined EAS was tried in the 5 patients with postoperative residual hearing. Two patients showed increase in their word discrimination score (WDS) under combined EAS compared to cochlear implants only. Their mean residual hearing threshold should be below 62.5 dB in the 250 Hz and 500 Hz. The other three didn’t benefit from the combined EAS. Their mean residual hearing threshold was 80 dB in the 250 Hz and 500 Hz.
Conclusion: Hearing can be preserved through soft surgery technique. Patients can benefit from combined EAS in term of increased WDS compared to cochlear implants only.