Responsiveness Of Cochlear Nerve To Electrical Stimuli In Children With Common Cavity Deformity And The Outcomes With Cochlear Implantation

ObjectiveTo investigate the responsiveness of the cochlear nerve to electrical stimuli in implanted children with common cavity deformity(CCD),and compare their cochlear implantation outcomes with children who have normal cochleas.MethodsStudy participants included 6 children with CCD who underwent cochlear implantation in our hospital since June 2016 to December 2018.Including four boys and two girls who ranging in age between 2.1 and 7.0 years(mean:2.6 years).Two subjects were implanted bilaterally,the others were implanted unilaterally.The media age for implantation is 1.2 years(ranging from 0.9 to 4.9 years).All subjects were implanted with a Cochlear Nucleus device with a straight electrode array(24REST)in the test ear.The electrode arrays were fully inserted in all patients.The control group included six children with normal cochlea.The hearing threshold and speech ability,hearing aids using history,cochlear implantation age,cochlear implant using history in the control group were similar to those in the CCD group.The electrically-evoked compound action potential(eCAP)was attempted for each intra-cochlear CI electrode using Custom Sound EP software(version4.3).The eCAP amplitude growth functions(AGF)were recorded at three electrodes along the electrode array.The aided hearing threshold,CAP score and SIR score were measured pre-operation and at 6 m,12 m,18 m and 24 m post-operation.The discrimination of Ling six sound and closed set speech performance were accessed after six months of implantation.The eCAP threshold,slope of the eCAP AGF and the outcomes of cochlear implantation were compared between groups using the SPSS 20.0 software.ResultsThe eCAP was recorded at all CI electrodes in control group(100%).In the study participants,the eCAP was recorded at some but not all CI electrodes(74.78%).The eCAP thresholds along the electrode array in the control group were 12.44±3.07,13.41 ± 2.03 and 9.34±2.41 nC respectively.The eCAP thresholds along the electrode array in the CCD group were 26.94 ±5.39,21.06±5.52,and 23.60±5.33 nC respectively.The eCAP thresholds in the CCD group were significantly higher than those in the control group(p<0.05).The slopes of eCAP growth function along the electrode array in the control group were 3.94±1.13,5.43±2.55 and 6.83±5.36.The slopes of eCAP growth function along the electrode array in the CCD group were 2.72±5.13,4.13±5.33 and 2.47±3.61.The slopes of eCAP amplitude growth function in the CCD group were significantly smaller than those measured in the control group(p<0.05).In the CCD group,the T levels in the MAP from low frequency to high frequency were 15.7±6.6,13.8 ± 4.9 and 13.9 ± 4.6 nC respectively,which was significantly higher than those in the control group(p<0.05);the C levels in the MAP from low frequency to high frequency were 34.2±12.6,31.6±10.8 and 28.9 ± 6.9 nC respectively,which was also significantly higher than those in the control group(p<0.05).The hearing thresholds with cochlear implantation were higher in the CCD group than those in the control group post-operation,and there were significant difference at the 6 m and 12 m.The CAP score and SIR score were lower in the CCD group than those in the control group.ConclusionChildren with CCD showed reduced cochlear nerve responsiveness to electrical stimuli.The cochlear nerve function in patients with CCD varied highly.Children with CCD can benefit from implantation,but their results are poorer than children with normal cochleas.