The Effect Of Reducing The Insertion Depth Of Low-frequency Region On Speech Recognition In Recipients With Cochlear Implants Using Bimodal Hearing

Background:Sensorineural hearing loss is one of the most common diseases of human disability. It does affect the quality of our lives, so the research on the treatment of sensorineural hearing loss is signality. The common ways for the treatment of sensorineural deafness are drug treatment, hearing aid and cochlear implants. The drug treatments, such as glucocorticoid, antithrombotic agent and vasodilators, have effects on some early lesions only. And the use of hearing aids require patients to retain some residual hearing. All of these conditions limit its application in the treatment of severe to profound sensorineural hearing loss. Along with the criterion of cochlear implant expanded, cochlear implant become the conventional therapy of severe to profound sensorineural hearing loss. But the traditional cochlear implantation has some drawbacks. Although it can solve the problem of hearing loss, it does not make the best of residual hearing in low-frequency region. And because of the expense and other reasons, most of cochlear implantation is unilateral. So the unilateral cochlear implantation will lose the binaural effect and weaken the sound localization and speech recognition ability. Therefore, the bimodal hearing implantation is in order to make the best of residual hearing to improve the treatment effect of binaural severe to profound sensorineural hearing loss.Bimodal cochlear implantation is the combination of a cochlear implant in one ear and a hearing aid in the other. This situation requires residual hearing in the ear with hearing aid. On the one hand, cochlear implantation can recover high frequency hearing in patients with hearing loss. On the other hand, hearing aid can amplify the low frequency sound,and make full use of the low-frequency residual hearing. Bimodal cochlear implantation improve the speech recognition, sound localization and musical perception ability in profound sensorineural deafness patients by head shadow effect,binaural summation effect and binaural squelch effect.The beginning of the last century 70’s, cochlear implantation entered the commercialization stage and aroused great attention around the world at that time. Scientists had devoted much of their research and the technology has been rapid development. In 1990, Jastreboff PJ published their results about the cochlear implantation research. They found that if the residual hearing exist in cochlear implant recipient’s contralateral ear, then it can improve the speech recognition ability by the combination of a cochlear implant in one ear and a hearing aid in the other. Since then, the combined application of cochlear implant and hearing aid will be exploring by otologist constantly. Then there were some ways proposed, such as the combined application of CI and ipsilateral HA, the combined application of CI and contralateral HA,the combined application of CI and bilateral HA. At present, the development direction of the combined application of CI and contralateral HA is the electric-acoustic stimulation system, such as austrian MED-EL company’s EAS device and Australian Cochlear company’s hybrid device. The electric-acoustic stimulation system can improve high frequency hearing by electric stimulation from cochlear implant. It can also amplify the low frequency hearing signal by hearing aid. Then they improve the ipsilateral hearing through synergistic effect. Moreover, the combined application of cochlear implant and hearing aid is bimodal hearing implant. More and more experts engaged in the correlation academic research from 1990 when jastreboff PJ found that combined application pattern. Although they acquire different data about this combined application pattern, the end outcome always points out that this combined application pattern can improve speech recognition and sound localization ability in Profound hearing loss patients. On the other hand, cochlear implant and hearing aid are fairly mature products, but the electric-acoustic stimulation system is still relatively immature in the world. So bimodal hearing implant has been widely used relatively.But all the present research are based on all the electrodes insert in the inner ear. There is no research about the effect after bimodal hearing implant with electrodes incomplete insertion. At present there are some reasons can explain why the electrodes of cochlear implant can not complete insert in the inner ear. It include the technical level of surgeon, the need of protecting the residual low frequency hearing, and some difficult factors(Congenital cochlear hypoplasia,cochlear ossification and so on). There will be more and more cochlear implant patients with congenital cochlear hypoplasia or cochlear ossification, when the criterion of cochlear implant is relaxing. But how to help the patients to get a better hearing recover if they happened the low frequency electrode incomplete insertion. Therefore, this research analysis the effect of reducing the insertion depth of low-frequency region on speech recognition in recipients with cochlear implants using bimodal hearing. It expect bimodal hearing can improve patients speech recognition ability, even the low frequency electrodes do not insert into the inner ear.Objective:We investigate the effect of reducing the insertion depth of low-frequency region on speech recognition in recipients with cochlear implants using bimodal hearing. Then we hope to confirm the change condition of bimodal hearing after reducing the insertion depth of low-frequency region and whether the bimodal hearing can improve speech recognition ability after reducing the insertion depth of low-frequency regionMethod:The research objects are 15 patients that receive cochlear implantations between March 2013 to February 2014 in our hospital, age 10-18 year old and average 13.7 years old. Accepting criteria is as follows:1.There is residual hearing in the non-implanted ear.Objects all wear hearing aids in their non-implanted ears and their usage times over 6 hours average in a day.2.The objects were in accordance with the criterion of guide for cochlear implantation (Changsha,2013) 3.The same skillful surgeon performed the operations of cochlear implantation. All SONATA/CD40+ standard electrodes were inserted in inner ear smoothly. Then the x-ray indicates all electrodes were inserted in the inner era and there is no complication after operations.4.The research objects came back to hospital for starting up the cochlear implant after operation I month. They also came back to hospital for debugging the cochlear implant at lst,3rd and 6th month after start up.5.The research objects receive the regular hearing and speech rehabilitation training over 9 month after start up cochlear implants. They now use oral communication as the main daily life communication.In the testing phase, we simulate low frequency segment electrodes did not totally implanted by used cochlear implants debug software "MAESTRO" to close the three apical electrodes in the cochlea (low frequency).All tests were performed in our hospital standard soundproof room (background noise <20db (A)). Mandarin Speech Perception System(MSPS) was used to perform single syllable, double syllable and short sentence test. Under the test, the same one research object must chose different groups of testing materials. Each group of test content just played once and the same one tester judged the retell of content from subjects whether they are correct or not. Then tester would Input the datas into MSPS and acquire the score(percentage).In the test, one subject would conducted 4 times tests(included single syllable, double syllable and short sentence test every time) in different state:1. unilateral CI 2.bimodal hearing 3. unilateral CI with inactivated the 3 apical electrodes 4.bimodal hearing with inactivated the 3 apical electrodes.This research adopts the self contrast method. There are different matched group in the test.1.Under the electrodes complete implanted state, bimodal hearing compared with the unilateral cochlear implantation through the data from complete implanted-unilateral cochlear implantation group and complete implanted-bimodal hearing group.2. Under the unilateral cochlear implantation state, complete implanted compared with incomplete implanted through the data from incomplete implanted-unilateral cochlear implantation group and complete implanted-unilateral cochlear implantation group.3. Under the bimodal hearing state, complete implanted compared with incomplete implanted through the data from incomplete implanted-bimodal hearing group and complete implanted-bimodal hearing group.4.Under the the electrodes incomplete implanted state, bimodal hearing compared with the unilateral cochlear implantation through the data from incomplete implanted-unilateral cochlear implantation group and incomplete implanted-bimodal hearing group.Statistical analysis was performed by SPSS 13.0 software. According to the Shapiro-Wilk test and homogeneity of variance test, data accord with normal distribution and homogeneity of variance. The paired data were analyzed by paired t test, P<0.05 had statistical significance.Result:1. Bimodal hearing compared with the unilateral cochlear implantation under the electrodes complete implanted state. Bimodal hearing have better speech recognition score than unilateral cochlear implant in all the three tests when electrodes were complete implanted. Complete implanted-unilateral cochlear implantation group:single syllable test 77.6%±7.3%,double syllable test 83.6%±10.4%,short sentence test85.4%±6.0%.Complete implanted-bimodal hearing group:single syllable test 82.8%±6.7%,double syllable 88.5%±8.4%,short sentence test89.3%±5.2%. There was significant difference between two related groups, P<0.05.2.Complete implanted compared with incomplete implanted under the unilateral cochlear implantation state. Incomplete implanted have worse speech recognition score than complete implanted in all the three tests when under the unilateral cochlear implantation state. Incomplete implanted-unilateral cochlear implantation group: single syllable test 57.9%±10.3%,double syllable test 58.6%±14.6%,short sentence test68.3%±6.7%.Complete implanted-unilateral cochlear implantation group:single syllable test 77.7%±7.3%,double syllable test 83.6%±10.4%,short sentence test 85.4%±6.0%. There was significant difference between two related groups, P<0.053.Complete implanted compared with incomplete implanted under the bimodal hearing state. Incomplete implanted have worse speech recognition score than complete implanted in all the three tests when under the bimodal hearing state, incomplete implanted-bimodal hearing group:single syllable test 70.2%±7.9%,double syllable test 73.7%±13.7%,short sentence test 76.4%±5.9%.Complete implanted-bimodal hearing group:single syllable test 82.8%±6.7%,double syllable test 88.5%±8.4%,short sentence test 89.3%±5.2%. There was significant difference between two related groups, P<0.054.Bimodal hearing compared with the unilateral cochlear implantation Under the the electrodes incomplete implanted state. Bimodal hearing have better speech recognition score than unilateral cochlear implant in all the three tests when electrodes ware incomplete implanted. Incomplete implanted-unilateral cochlear implantation group:single syllable test 57.9%±10.3%,double syllable test 58.6%±14.6%,short sentence test68.3%±6.7%.Icomplete implanted-bimodal hearing group:single syllable test 70.2%±7.9%double syllable 73.7%±13.73%,short sentence test76.4%±5.9%.There was significant difference between two related groups, P<0.05.Conclusion:1. These findings confirm previous studies which have found cochlear implant can improve speech recognition ability by use hearing aid in contralateral ear.2. No matter bimodal hearing or unilateral cochlear implantation, reduce the insertion depth of low-frequency region will lower the speech recognition abilities of cochlear implant patients.3. This research confirmed that bimodal hearing can improve the speech recognition ability relative to unilateral cochlear implantation when patients in the state of electrodes incomplete implant. So this finding prove a new way to improve speech recognition ability when patients are in the state of electrodes incomplete implant.