Characterization of Electrically Evoked Compound Action Potential Amplitude Growth Function in Cochlear Implant Users

A multichannel cochlear implant (CI) is designed to take advantage of the tonotopic arrangement of auditory nerve fibers within a cochlea. The electrically evoked compound action potential (ECAP) is a safe and reliable objective measure for qualifying neural survival and local spatial resolution in the cochlea. The present study was aimed to explore the effect of recording position on the ECAP Amplitude Growth Function (AGF). The stimulating electrode (EL) was fixed at EL8, in the middle of the electrode array in 6 Clarion II or HiRes 90K subjects. The ECAP AGFs were obtained respectively from two recording positions (EL6 and EL10) using monopolar stimulation mode. The result showed that, in all subjects for both EL6 and EL10 recording positions, the ECAP is a linear function of stimuli level (Mean R²= 0.96, standard deviation =0.06). Moreover, there was a significant correlation of the ECAP AGFs recorded from EL6 and EL10. These results demonstrate the fundamentals of the electrical hearing and will be utilized in the clinical application for diagnosing neural degeneration of CI users.