| Objective: 1.To study the effect of noise and mechanical vibration damage on the morphology and function of the cochlear sensory cells before the electrode is implanted through round window of the mini-pigs and a part of the round window niche is abraded by an electric drill.The threshold and amplitude of Cochlear microphonic potential observes microstructure changes of the cochlear tissue,compare and analyze the difference in the influence of the two surgical methods of round window niche abrasion and retention on the morphology and function of the cochlear tissue.The new selection provides a reference for new choices of Cochlear implant.Methods: 1.6 small pigs were divided into 2 groups,round window niche retention group and round window enlarging(RWE)group.Under general anesthesia,we test he ABR threshold(Click,500 Hz,1kHz,2kHz,4kHz,8kHz).In the approach of cochlear implantation(with probe electrode),the round window is exposed immediately after the round window niche is retained/abraded.After entering the lengths of 1,3,and 5 marks slowly,intraoperative round window electrocochleography is performed with silver ball electrodes to measure and analyze the threshold and amplitude change of Cochlear microphonic potential.After the last CM threshold test,this side ear ABR threshold(Click,500 Hz,1kHz,2kHz,4kHz,8kHz,)were measured at last.After collecting the last hearing data,cochlea of each test animal is immediately took out and fixed with fixative.observe the changes in the cilia of the inner and outer hair cells and the epidermal plate issue.on the scanning electron microscope.Results: 1.ABR test results: Before electrode implantation,the round window(RW)group and round window niche enlarge(RWE)group under acoustic stimulation at click,500 Hz,1kHz,2kHz,4kHz,8kHz sound stimulation ABR threshold(dB SPL)shift: RW group: 45 ± 0,65 ± 8,45 ± 8.66,46.67 ± 10.41,55 ± 10,50 ± 8.66;RWE group: 53.33± 5.77,73.33 ± 10.41,60 ± 5,55 ± 5,55 ± 0.After electrode implantation,the ABR threshold(dB SPL)of the round window(RW)group and the round window niche enlarge(RWE)group under acoustic stimulation at click,500 Hz,1 kHz,2 kHz,4 kHz,and 8 kHz are: RW group: 88.33 ± 7.64,110 ± 25.99,106 ± 27.54,111.67 ± 18.92,118.33 ± 7.63,115.33 ± 13.23;RWE group: 108.33 ± 14.43,125 ± 0,125 ± 0,118.33 ±11.55,118.33 ± 11.54,125 ± 0.Under click sound stimulation and 500 Hz,1kHz,8kHz pure tone sound stimulation,the ABR hearing threshold of the round window niche enlarge group was higher than that of the round window niche retention group,and at low frequency region(click,500 Hz,1kHz)the difference was more obvious.2.CM threshold amplitude detection results: 1.The CM thresholds of two groups of experimental animals with different implantation depths(0mm,6.5mm,11.5mm,20mm)are: RW group(dB SPL): 105±7,100±27.84,100±26.45,101.67±28.43;RWE group:83.33 ± 32.15,116.67 ± 14.43,125 ± 0,125 ± 0;CM of two groups of experimental animals with different implantation depths(0mm,6.5mm,11.5mm,20mm)he amplitudes are: RW group: 3.99 ± 3.21μV,6.07 ± 9.11μV,5.33 ± 7.46μV,2.09 ± 3.17μV;RWE group: 12.31 ± 14.3μV,1.04 ± 1.39μV,0.37 ± 0.308μV,0.27 ± 0.14μV.From the mean value of CM threshold,from the mean point of view of CM threshold,the threshold of RW group is higher than that of RWE group when implanting 0mm.,but the threshold of RWE group was 20 dB SPL higher than that of RW group when implanted at 6.5,11.5,and 20 mm.The CM amplitude of the RWE group was higher before the implantation electrode,but the average value of the RW group was higher than that of RW after 6.5 mm,and the amplitude was larger.3.Electron microscope morphological observation: 1.Tissue fragility: RWE group has a large number of tissue missing areas,the tissue loss is more serious,the brittleness becomes larger,and the area where the tissue loss is concentrated is located in the middle rotation.2.Change of inner and outer hair cells: using the contralateral ear as a control,RW group: the cilia of the inner and outer hair cells were neatly arranged at the bottom,and the microvilli on the surface of the inner pillar cells increased,and no significant abnormalities were seen;The ciliary arrangement is disordered,lodging,and the lysis becomes short and missing,resulting in inflammatory clumps.Some outer hair cells(cilia)are balloon-like degeneration,destroying the lysis,and missing,and the microvilli on the surface of the inner pillar cells increase;the bulging vesicles are promoted by the inner hair cells.The outer hair cells were not significantly different.RWE group: the cilia of inner hair cells at the bottom were significantly shortened,fused with each other,arranged in disorder,fell down,and the microvilli on the surface of the inner column cells increased;the ciliary dissolution of the inner hair cells in the transfer became shorter,and the absence was worsened,and some Deiter cell fingers were separated from the outer hair cells.Microvilli fusion,increased microvilli on the surface of the inner column cells,part of the inner hair cell cilia missing at the end,and a small amount of the bulging vesicles remaining on the outside,no significant difference was found.Conclusions: 1.Cochlear implantation with round window niches not mulled can retain certain residual hearing and inner and outer hair cell functions.2.The mechanical damage caused by the mulling round window niche will seriously affect the function of the inner and outer hair cells.The damage of the inner hair cells is greater than that of the outer hair cells,and the CM is basically undetectable. |
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