Research And Basement Membrane Electrode Output Frequency Characteristic Frequency Mismatch Cochlear Implant

Objective:To determine whether has the phenomenon of the mismatch between electrode assigned frequencies and the characteristic frequencies located in basilar membrane in the CI users in two methods. One method is testing CI users-identification capability to three different sound:low frequency, intermediate frequency and high frequency through changing CI channels to activation or partially inactivation.Another method is by the methods of temporal bone CT scan and3D reconstruction of the cochlea. And test the CI users" behavior audiometry and speech audiometry. To explore the relationship between the mismatch and implant length of the electrode and speech recognition rate.Materials and methods:To collect10Australian cochlear implanted users in the Yunnan provincial deaf rehabilitation school to get the imaging and audiology data of their preoperative and postoperative. Set up4different electrode activation conditions as follows:condition A, electrodes are all active state; condition B, inactivation from20to22electrodes that is closing the frequency range of the drum1s sound; condition C, inactivation from11to16electrodes that is closing the frequency range of the wooden fish" s sound; condition D, inactivation from1to11electrodes that is closing the frequency range of the bell’s sound, and separately test sounds identification ability of drums, wooden fish and bell. Calculate the length of cochlear implant electrode and the contralateral cochlear length with the help of the temporal bone CT scan and three-dimensional reconstruction. Test the subjects" binaural bare auditory threshold and close site of the consonant and the vowel recognition rate in the free field.Results:1.Ten subjects all have the phenomenon of the mismatch. Ten of them found the mismatch phenomenon in low frequency. Six of them found the mismatch phenomenon in intermediate frequency. Nine of them found the mismatch phenomenon in high frequency. Five of them found the mismatch phenomenon in low frequency, intermediate frequency and high frequency simultaneously. One subject found the mismatch phenomenon in low frequency, intermediate frequency simultaneously. Four subjects found the mismatch phenomenon in intermediate frequency and high frequency simultaneously.2. Ten subjects’ electrodes were implanted in the scala tympani without discount and bending. The depth of insertion of the electrode is17.90-25.00mm, an average of20.18±2.18mm.And the length of the cochlea are28.96-32.00mm, the average is30.26±0.92mm.3. We discovered the phenomenon of the mismatch in this group of all the subjects by the Greenwood formula. Each subjects’ mismatch rate is73-95%, the mean is85±6%.(The mismatch rate is percentage of the ratio between the mismatch number of electrodes and total number of electrodes. The mismatch rate is higher, the more serious that mismatch)4. Vowels recognition rate of ten subjects was44%-100%, the average73.70±16.43%.Bivariate correlation analysis of the mismatch rate and vowels recognition rate, the result is P<0.01, there is a negative correlation between the mismatch rate and vowels recognition rate.5.Consonant recognition rate of the ten subjects was40%-100%, the mean and the standard deviation is80.70±18%, Bivariate correlation analysis of the mismatch rate and consonant recognition rate, the result is P<0.01, there is a negative correlation between the mismatch rate and consonant recognition rate.Conclusion:1. We found the phenomenon of the mismatch between electrode assigned frequencies and the characteristic frequencies located in basilar membrane in all the CI users of this group with audiology and imaging method.2. The mismatch rate is negatively correlated with the consonant recognition rate and the vowels recognition rate.3. The audiology method in this study to detect the mismatch phenomenon as a qualitative and locating detection, can understand the mismatch position being at the regional of low frequency, intermediate frequency or high frequency high. And the imaging method detection as a more accurate positioning and quantitative detection, can realize whether has the phenomenon of the mismatch in each electrode.