Preoperative Assessment Of CI And Hearing Protection Of Drug-loaded Electrodes In Children With CND

Objective:The aim of this study is to evaluate auditory pathway,auditory cortex function,and cochlear nerve function via CT,magnetic resonance imaging(MRI),functional magnetic resonance imaging(f MRI)and electrical evoked auditory brainstem response(EABR)in children with cochlear nerve deficiency(CND)before cochlear implantation(CI).Secondly,using CI guinea pig model,the protective effect of poly-lactic-co-glycolic acid(PLGA)coated drug-loaded electrode on hearing loss after CI is studied.Methods:Part ?: Of 6 children with bilateral profound sensorineural hearing loss,bilateral stenosis of the internal auditory meatus in 4 cases,unilateral stenosis of the internal auditory meatus in 1 case and normal internal auditory meatus in 1 case were diagnosed by CT.In 3 cases,oblique sagittal MRI reconstruction of the internal auditory meatus showed only facial nerve and vestibular nerve presentation.6 cases were diagnosed as CND by imaging,among which f MRI or EABR underwent in3 cases,respectively.All children received unilateral CI and were followed up for at least 1 year after hearing and speech rehabilitation.Part ?: PLGA coated drug-loaded electrode with dexamethasone(DXM),Aracytine(Ara-C)and nicotinamide adenine dinucleotide(NAD+)were implanted into the guinea pig model,respectively.ABR thresholds of 4,8,16,24 and 32 k Hz were recorded at the day 0,7,14,28 and 90 after CI.Results:Part ?: fMRI was examined in 3 cases with CND.The result showed that the right auditory cortex was activated in the first case after sound given to the left ear but no activation was found in the left cortex when sound given to the right ear.It showed activation in bilateral transverse temporal gyrus while sound was given to the left,right and both ears at 2000 Hz in the second case.There was no activation in both auditory cortexes in the third case.EABR was detected in 2 of 3 cases with elicited V wave.6children received audiological and speech evaluation at 1 month,6 and 12 month after CI.Of 6children,the hearing level was improved within 6 months after surgery in 4 cases with the threshold in sound field of 48.15±6.60 d B HL,and both MAIS and CAP scores improved.However,SIR score improvement is limited in 3 cases.The hearing level was improved in 1 case,however,speech rehabilitation was poor mainly due to the older age.Part ?: Compared with the control group,the ABR thresholds of DXM/PLGA and Ara-C/PLGA loaded electrodes decreased significantly(p<0.001),however,there was no significant difference in NAD+/PLGA group.Conclusion:The comprehensive application of preoperative imaging and electrophysiological evaluation in children with CND could accurately assess the integrity of auditory pathway and existence and function of cochlear nerve,which is of important reference value for surgical intervention and prognosis.There were significant differences in the outcomes of auditory and speech rehabilitation after CI in children with CND.The PLGA drug-loaded electrode can release drugs stably in CI guinea pig model in which DXM amd Ara-C have protective effects on postoperative hearing loss.