Establishment And Rudimentary Application Of The Method Of Recording ECAP,EABR And EMLR In Cochlear Implantation

Background and Purpose:Cochlear implantation is an effective method of auditory rehabilitation for profoundly hearing-impaired individuals who do not receive adequate benefit from hearing aids, but is expensive. So, it has become the concern of doctors and patients to make the most rational use of limited medical resources. Preoperative objective hearing tests consist of DPOAE, ABR, ASSR and aid-audiometry test showed no residual hearing without language training in patients with preoperative hearing and speech score perceived ambient sound. Such patients'postoperative hearing maybe not good, which can easily generate the doctor-patient conflicts. The patient with "no residual hearing" may be a cochlear malformation or patient with very high hearing threshold, the conventional acoustic stimulation is not sufficient to cause auditory nerve responses leading to the preoperative hearing could not be determined, we can not explain the patient is not suitable for the cochlear implant. Electrical stimulation of the auditory evoked potentials such as ECAP, EABR and EMLR can reflect the auditory pathway physiological conditions. Preoperative electrical stimulation of the auditory evoked potential test in cochlear implant can learn about the patient's real residual hearing, for cochlear implants to escort.The aim of the current study was to establish the method of preoperative electrical stimulation of the auditory evoked potential including ECAP, EABR and EMLR, to assess the cochlear implant patient's physiological function of auditory pathway from the cochlea to the auditory cortex, in order to guide the complex and difficult cochlear implant, especially patients with no residual hearing, preliminary estimates the patients' postoperative hearing and speech rehabilitation.Objects:There were26CI users in the study group (8males and18females), aged from11months to43years, the median age of24months. Cochlear implantation were completed during February2010to February2011in our hospital, the cochlear company Nucleus24R [CA or ST] multi-channel cochlear were implanted, All patients showed no residual hearing by objective hearing tests including DPOAE, ABR, ASSR and aid-audiometry test.2O cases of pre-lingual deafness,6cases of post-lingual deafness. Preoperative imaging studies of11patients with normal cochlear morphogenesis,4patients with bilateral vestibular aqueduct,5patients with bilateral cochlear Mondini malformation, internal auditory tract narrow in3cases,3cases of common cavity deformity. At the same time, we screened26patients with residual hearing and language-based as the control group. Pairing based on age, gender, hearing loss time, implanted ear and cochlear morphology. All patients under MRI examination of cochlear water imaging, visible to the auditory nerve and cochlear cavities exist, and are unilateral implantation except for1case with internal auditory tract narrow.Part I:Establishment and preliminary application of the method of ECAP before cochlear implantationMethods:After anesthesia, conventional cochlear implant surgery in cochlear tympani scala fenestration (common cavity in vestibular window), self-made multi-channel test electrode was inserted into the tympani scala, and connected to the homemade electrical stimulation generator and computer pre-installed Custom Sound TM the EP2.0software, The electrode No3were selected, change the stimulation parameters to the neural response telemetry (NRT), the neural response telemetry preliminary understanding of the state of the auditory nerve function; Electrical stimulation pulse was gived above the reaction threshold with stimulus intensity to5CL step decrement or increment, and the ECAP waveform and threshold were automatically recorded. After cochlear implantation, ECAP waveform and threshold were automatically recorded by business electrode. Calculating the positive rate of the test electrodes and the commercial electrode; estimating the test electrode-induced ECAP waveform threshold and the N1wave latency, and comparison with the ECAP waveform induced by commercial electrode; two electrode test income threshold and boot C values of the correlation study the two electrode-induced ECAP threshold and C values, conducted statistical analysis of data.Results:The positive rate of ECAP leads to65.38%and69.23%from test electrode and commercial electrode in the same group,(considering more cochlear malformation patients in our study lead to the low rate); In study group, the ECAP average thresholds were (172.11±16.78) CL and (171.05±17.84) between two kinds of electrodes, the two surveys are not statistically significant difference (P>0.05); and C values after boot (178.36±22.14CL) significantly correlated(r=0.746), but rate was lower. The latency of N1wave through the two electrodes in the study group was as follows:0.292±0.063ms and0.287±0.060ms, it was not significantly different (t=1.694, p=0.107>0.05); the ECAP thresholds through two electrodes in study group and boot C value were statistically no significant difference (F=0.173, p=0.842), the multi-channel test electrode is suit for electrophysiological testing. In addition, the positive rates of ECAP lead to no significant differences between the study group and the control group, which indicated the objective examination about pre-operative residual hearing was not accurate. However, the ECAP thresholds in two groups were172.11±16.78CL and158.95±15.42CL, it was significantly different (P <0.05), indicating that the spatial ganglion distribution and physiological status in control group were better than study group. The ECAP can preliminary evaluated the physiological functions of the primary auditory center.Part II:The EABR testing and clinical application before cochlear implantationMethods: The surface recording electrodes were placed on the two groups under complete aesthesia, connected to the evoked potential device. The self-made multi-channel test electrode was inserted into the tympani scala and connected to the homemade electrical stimulation generator and computer pre-installed Custom Sound TM the EP2.0software, with language processor connected to the triggering port of the auditory evoked potential device. Selecting the EABR mode (reference Cheng Jingning' methods), recording the EABR waveform, threshold, calculating the positive rate and I/O curve slope of V wave. One month after operation, collecting T, C value; Contrasting EABR, ECAP positive rate in the same group; and correlation analysing EABR threshold and ECAP threshold, EABR thresholds and C values. Contrasting EABR threshold, I/O slope of V wave between the two groups, compare the I/O slope of V wave between patients with normal cochlea and deformity cochlear; statistical analysis data.Results:Two groups of52patients,49cases meaningful EABR waveform were elicited (wave V as a reference),3cases of stenosis of the internal auditory canal cochlear implant was not elicited waveform in study group, and all patients were implanted except one cases of stenosis of the internal auditory canal. The positive rate in study group leads to88.46%, control group leads to100%, higher than that of ECAP. The outcome of EABR was in line with the post-operative boot auditory reaction, indicating that the EABR can be used as a tool for screening cochlear indications. The EABR thresholds (163.82±16.21CL) in study group were higher than that in the control group (148.41±15.38CL); The I/O curve slope of V wave of normal cochlea patients were better than that with deformity cochlear, and the control group (0.041364±0.013623) is better than study group (0.035227±0.013918), there were statistical differences between the two groups (P<0.05). The EABR thresholds and boot C values were significantly correlated (r=0.915) in the same group, can help to estimate the value of C. Part III:Establishment the method of EMLR in cochlear implantationMethods:First,6cases of normal hearing healthy subjects were selected to record short-sound evoked auditory middle-latency response (AMLR), as the control of morphology and latency of MLR by electrical stimulation. Before operation, devices were connected according to the EABR test. Selected the EABR mode, changed the stimulation parameters to EMLR mode, with monopolar biphasic electrical stimulation pulses, Alternation stimulation,50～100μs pulse width, stimulation frequency of11Hz, the stimulation intensity decreased or increased from20CL above the strength of the NRT threshold to the reaction threshold with a step of5CL, recording EMLR waveform by auditory evoked potential device. The wave amplitude, latency, threshold, positive rate were calculated and classificated according to the EABR classification.1month after operation, we collected T, C value, assessed patients'hearing and speech rehabilitation through CAP scores tool12month later; Correlation analysed ECAP thresholds, EABR thresholds, EMLR thresholds and T, C value within the same group. Correlation analysed the EMLR classification and the CAP scores; Contrasted EMLR thresholds, postoperative CAP scores between two groups.Results:The typical AMLR waveforms can be recorded by the composition of five waves in the6cases of normal hearing healthy subjects, with an average response threshold of (12.5±8.6) dB nHL, close to the behavioral audiometric threshold (10.8±7.3) dB HL; According to the AMLR test, we established the method of pre-operative EMLR for the first time, the EMLR waveform were similar to the AMLR. Two groups of52patients,49cases meaningful EMLR waveform were elicited (wave Pa as a reference),3cases of stenosis of the internal auditory canal cochlear implant was not elicited waveform in study group; the positive rate of EMLR in study group was88.46%, same to EABR, higher than ECAP. In study group, the EMLR average threshold (151.32±14.31CL) is lower than the the ECAP average threshold (172.11±16.78CL)(P<0.01), EMLR thresholds and boot T,C values (correlation co-efficient respectively: r=0.905, r=0.862) have a significant correlation values, closer to the T value.12months after booting, the EMLR waveform was divided into4level according to the EABR classfication, and compared with the boot CAP scores, the average boot CAP scores (6.52±0.98) and the intra-operative EMLR levels (3.5±0.80) were significantly correlated (spearsman:0.673). In addition, the EMLR thresholds (151.32±14.31CL) in study group were higher than the control (140.68±12.84CL)(P<0.01); we compared the EMLR levels (U test:P=0.588) and CAP scores (U test:P=0.179) between the two groups, there were no statistically significant difference. Indicating that the EMLR could assess physiological status of higher level auditory center was correlated with hearing and speech development.Conclusions:ECAP can evaluate if the implanted electrode is working properly, and if the spiral ganglion meet the need for cochlear implant; the positive rate of EABR leads to high, can reflect the integrity of auditory pathways from the spiral ganglion to the brain stem; EMLR reflect the physiological status of primary auditory cortex, assist in evaluating the integrity of the auditory pathway.Our studies have achieved the following objectives:1. Successfully established the methods of intra-operative electrical stimulation auditory evoked potentials (ECAP, EABR, EMLR) in cochlear implantation for the first time.Systematically assess the physiological state of auditory pathway from the hair cells to the auditory cortex in bilateral severe sensori neural deafness patients;2. Successfully invented a multi-channel test electrodes and electrical stimulus generator for the first time. Successfully integrated the electrical stimulation system and evoked potential recording system, to simplify devices and reduce the recording time.3. Successfully established the methods of pre-operative ECAP for the first time, to evaluate the physiological status of the spiral ganglion in patients with no residual hearing.4. Detected the EABR and calculated the Ⅴ-wave I/O curve slope in patients before the cochlear implant through the test electrode, to judge the physiological conditions from auditory nerve to brainstem; the positive rate is high, can guide cochlear implantation in difficult cases.5. Successfully established the pre-operative EMLR detection method for the first time, can detect the physiological status of the primary auditory cortex; estimate the preliminary post-operative hearing and speech rehabilitation capacity according to the theEMLR classification results; theoretically support the the auditory brainstem implant in the future.We successfully established the method of intra-operative ECAP, EABR, EMLR monitoring in cochlear implantation. This technique can intra-operative evaluate the auditory pathway, preliminary predict the speech perception outcome after cochlear implantation; provide confidence betwween clinicians and patients. The positive rate of ECAP in patients with cochlear malformation lead to low, but not be deemed to no residual hearing, only the postoperative outcome is worse than patients with normal cochlea; The positive rate of EABR EMLR lead to higher rate, can assist in pre-operative screening the cochlear indications; EMLR correlate with the speech perception outcome after cochlear implantation, can assist in evaluating the postoperative rehabilitation effect.