| Cochlear Implant (CI) is the unique medical and bioengineering equipment for the totally deaf persons to rehabilitate their aural/oral communicative abilities. Chinese ENT surgeons and audiologists have recognized its wider perceived applications and achievements throughout the world. But the benefits from a cochlear implant vary enormously between individuals. The challenge for the clinicians is to explain why there is such a wide variability of outcome and to develop ways to more accurately predict potential benefit preoperatively. A cochlear implant is an electrical device that takes over the function of a damaged cochlea. The auditory physiological properties evoked by electrical stimulation via a needle electrode placed onto the promontory or the electrodes implanted in the inner ear are believed to be an indicator of the speech perception of CI users.The steady increase of cochlea implant cases in China in the past few years provides an opportunity in collecting robust outcome measures in a short period. It would be advantageous for clinical investigation about the key factors in making precise predictions of post-implantation benefits. Unfortunately, there is very little in the way of standardized test material to be used for speakers of Mandarin, the clinical research concerning accurate comparisons of performance and comparisons across languages becomes more difficult.The electrically evoked compound action potential (ECAP) is thesynchronized response of peripheral auditory nerve to electric current pulses delivered by intra-cochlear electrodes. The study investigated its characteristics in the sensitivity, growth, and temporal, spatial properties of all the adult post-lingual deafened CI recipients who implanted in our hospital. We also measured their speech recognition scores on tests of Mandarin tones, monosyllabic, and sentences. The relationship between electrical auditory properties and speech perceptual performance was analyzed in order to determine the key factors of electrical auditory characteristics that would influence CI outcomes. The study consists of three parts:Part One:Compilation of Mandarin Test Material and Digital Edit of KXYThe KXY monosyllabic word lists, KXC multisyllabic word lists, KXJ sentence lists which were published as appendixes in the Chinese National Standard GB/T15508-1995: Acoustics?Speech articulation testing method were selected as the Mandarin test materials for evaluation of speech perceptual abilities of CI recipients in our study. The recording, edit and normalization of test items were digitally processed and all test materials were burned into CD finally.On account of facility in clinical practice, we simplified the 75-items KXY monosyllabic lists into 25-items lists based on Phonemic Balance consideration. We also compiled Mandarin spondee tonal lexical neighborhood test lists based on the assumption of the Neighborhood Activation Model (NAM).Part Two:Protocol of ECAP recordingThis part outlines a series of experiments using Neural Response Telemetry (NRT) to measure the electrically evoked compound action potential (ECAP). 90 Nucleus 24 cochlear implant users participated in the study. ECAP thresholds and growth function slopes of 16 CI recipients were measured for all electrodes at post-operative 1,2, 3-months mapping sessions,Results: 1). We manipulate the optimized stimulating and recording parameters to elicit the ECAP, 91.1% of all 90 recipients showed good ECAP morphology in total 22 electrodes; 2). The shape of ECAP amplitude growth function looks like /. When a linear fit was applied to the amplitude growth function data to determine threshold and slope, the saturated and sub-threshold responses had to be excluded; 3). The slope of ECAP growth function was higher in the apical region of the cochlea, while ECAP threshold was lower in the same region; 4). There was considerably less change of ECAP over the subsequent post-operative time intervals.Conclusion: 1). ECAP threshold should be determined by regression of...
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