Relative Electrophysiologic Study Of Cochlear Implant

Doing relative electrophysiologic study before and after cochlear implant is important for evaluating hearing function and objectively adjusting processor post-operatively, or electing candidates of cochlear implant pre-operatively.After cochlear implant, there are two aspects that should be mainly focus on. First, assessing the function of auditory conductive system. Second, adjusting cochlear implant processor periodically. At present, these work is mainly carried out by subjective tests. But these methods are only suitable for elder patients, as for little children who do not have subjective judging capacity, adjustment through these methods will be very difficult. This shortcoming can be surmounted by using objective methods.Speech recognition ability of cochlear implant patients are influenced by speech encoding strategy. There are different speech and hearing performance between patients who use different encoding strategies, thus test results between different encoding strategies can not simply be analogized. At present, there are still not systemic studies about objectively adjusting cochlear implant processor using advanced encoding strategy (ACE strategy) postoperatively.This research is planed to test cochlear implant patients who use this new ACE strategy. Firstly electrically evoked auditory brain-stem response (EABR) was tested to find the influence of using different test parametes on EABR waves, and hearing system function of cochlear implant patients will be evaluated using EABR test. ThenEABR, electrically evoked compound action potential (ECAP) and electrically elicited stapedius reflex (ESR) will be researched so as to study the feasibility of adjusting processor using objective methods.Doing promontory EABR test before operation can help selecting candidates for cochlear implant, selecting operation ear side. For overcoming the difficulty of recording promontory EABR, animal promontory EABR test will be carried out in this research at the same time in order to get the mode of reliably recording promontory EABR.This article consists of three parts.Part I Evaluating auditory system function of cochlear implant patients using EABR testEABR will be recorded in 53 cases who received Nucleus 24 cochlear implant using ACE strategy. Our purposes include: (1) studying the influence of different test parameters on EABR waves. (2) obtaining normal values of EABR waves in these patients. (3) evaluating auditory system function of these patients by comparing ECAP test done simultaneously in this research.Data was analyzed using SPSS 10.0 software. The statistics method is paired-samples T test.Results:1. Waves I, II, III, IV, V were recorded in EABR test. With stimulating intensity decreasing, the amplitude and atency of EABR waves decreased and prolonged respectively. The latency of EABR waves was shorter than those of corresponding ABR waves.2. The influence of different test parameters on EABR waves were as follows:(1) Stimulating artifacts using mono-polarity stimulating mode was higher than using alternating polarity stimulating mode.(2) With stimulating frequency increasing, latencies of EABR waves prolonged. Amplitude of EABR waves lowered significantly when stimulating frequency was 99Hz.(3) Stimulating artifacts were higher using isolateral recording mode than usingcontralateral recording mode.(4) Low cut-off 100Hz frequency unchanged, latencies of EABR V waves got shorter or kept stable when high cut-off frequency changed from 1.5KHz to 3KHz or changed from 3KHz to 25KHz respectively. EABR waveform was interfered by high frequency noise when stimulating frequency was 99Hz. High cut-off 3 KHz frequency unchanged, latency of EABR V waves were stable when low cut-off frequency changed from 100Hz to 0.002Hz.3. The threshold of EABR tested using pulse width 25 us/phase current was higher than that of EABR using pulse width 50us/phase or 75 us/phase current(P<0.01). The threshold of EABR tested using pulse width 50us/phase current was higher...