術後2年以降に聴力増悪をきたした残存聴力活用型人工内耳（Electric Acoustic Stimulation: EAS）例

抄録

We report the case of a 53-year-old female patient who underwent electric acoustic stimulation (EAS), which was followed by late-onset deterioration of residual hearing in the operated ear. She visited our hospital with a history of progressive bilateral hearing loss since she was in her thirties. A pure-tone audiogram showed bilateral high-frequency hearing loss, and the monosyllable test using a hearing aid showed values of 40% in the right ear and 50% in the left ear. She underwent cochlear implantation in her left ear with a round window approach using the MED-EL FLEX EAS electrode. Residual hearing on the operated side was preserved until 2 years after the EAS operation. However, she began to experience hearing deterioration from 2 years 4 months after the operation. Systemic steroid treatment proved ineffective. The stimulation procedure was changed from EAS to electric stimulation (ES) alone, because acoustic stimulation (AS) had already proved ineffective. A few months later, the patient recovered her speech discrimination ability to the same level as that during the EAS. We consider that the hearing deterioration resulted from two factors; late-onset extrinsic damage of the cochlea due to surgery or as part of the natural intrinsic course of sensorineural hearing loss. The long-term outcome of EAS is still unclear. Meticulous observation of the hearing ability by a speech therapist as well as neuro-otologist is needed for EAS patients.