脉冲噪声暴露后大鼠听皮层神经颗粒素的表达研究

目的揭示脉冲噪声暴露后不同时期大鼠听皮层神经颗粒素(neurogranin,Ng)表达的变化。方法将50只成年SD大鼠随机分为5组:正常对照组及脉冲噪声暴露后3、7、14、28天组,每组10只。脉冲噪声暴露条件为:平均压力峰值156dB SPL,脉宽为0.25ms,暴露50次,每次间隔6s。于噪声暴露前及噪声暴露后即刻、3、7、14、28天检测各组大鼠ABR反应阈,同时,应用Western blot方法检测各组大鼠听皮层中的Ng的含量。结果与对照组相比,各组大鼠噪声暴露后即刻、3、7、14、28天各频率ABR反应阈均明显提高(P<0.05),噪声暴露后第7天,各频率ABR阈值有所恢复,第14天时趋于稳定;与对照组(0.68±0.08)比较,噪声暴露后第3、7、14天组大鼠听皮层中Ng的含量分别为0.96±0.05、1.11±0.05、0.78±0.04,显著高于对照组,第28天组为0.36±0.03,显著低于对照组,差异均有统计学意义(P<0.05)。结论噪声暴露后,大鼠ABR反应阈明显升高,听皮层Ng的表达呈现一个先上升后降低的过程,提示脉冲噪声刺激对大鼠听觉系统产生了一定持续性的影响,听皮层出现突触可塑性变化。     

慢性噪声暴露对大鼠听皮层及海马脑区胰岛素样生长因子－1表达的影响

目的：观察慢性噪声暴露后大鼠听皮层及海马脑区胰岛素样生长因子－1（insulin－like growth fac-tor－1,IGF－1）的表达,探讨其在长期噪声性中枢神经系统损伤中的作用。方法成年健康雄性 Wistar 大鼠16只,随机分为噪声组和对照组各8只,噪声组暴露于100 dB SPL 白噪声28天,每天4小时,制成慢性噪声暴露模型,对照组不予任何处理。造模结束后检测两组大鼠 ABR 反应阈,并采用免疫组织化学染色方法检测 IGF－1在听皮层和海马的表达。结果噪声组造模结束后 ABR 反应阈（80．62±4．58 dB SPL）较对照组（38．75±3．54 dB SPL）明显升高（P＜0．05）,听皮层及海马脑区 IGF－1阳性神经元数目和表达强度均较对照组显著增加（P＜0．05）。结论慢性噪声暴露可以使听皮层及边缘系统海马脑区 IGF－1表达增高,这可能与其对中枢神经系统噪声性损伤的保护作用有关。     

长期注射水杨酸钠大鼠下丘EphA4的表达

目的：通过观察长期水杨酸钠作用后大鼠ABR及下丘EphA4mRNA表达变化,探讨下丘EphA4表达在水杨酸钠耳毒性中的作用。方法将30只健康成年雄性SD大鼠随机分为5组,每组6只：正常对照组（不予任何处理）,肌注7天组（肌肉注射水杨酸钠175 mg／kg,每天2次,间隔8小时,连续7天）,肌注14天组（水杨酸钠用法同前,持续14天）,恢复14天组（肌注水杨酸钠14天后,停药恢复14天）,恢复28天组（肌注水杨酸钠14天后,停药恢复28天）。对各组大鼠分别于相应时间点进行 ABR 检测后处死并迅速分离下丘,采用实时荧光定量PCR（real－time PCR）的方法检测各组大鼠下丘中EphA4mRNA表达。结果①肌注7、14天组大鼠的ABR反应阈分别为38．33±3．73、44．16±1．86 dB SPL,较对照组（30．83±1．86 dB SPL）明显升高（P＜0．05）;恢复28天组大鼠的ABR反应阈（32．50±2．50 dB SPL）与对照组（30．83±1．86 dB SPL）相比,差异无明显统计学意义（P＞0．05）;②肌注7天组和恢复14天组大鼠下丘 EphA4mRNA 表达（分别为：0．69±0．11、0．67±0．09）均低于对照组大鼠（0．99±0．01）（均为P＜0．05）;恢复28天组大鼠下丘EphA4mRNA表达（0．88±0．04）与对照组大鼠比较差异无统计学意义（P＞0．05）。结论长期注射水杨酸钠后大鼠下丘的 EphA4表达呈可逆性下降,且与水杨酸钠注射后大鼠听功能损伤的变化一致,推测下丘神经元轴突中EphA4参与了水杨酸钠耳毒性的机制。     

慢性噪声暴露对大鼠行为学及海马区5－HT1A受体表达的影响

目的：观察慢性噪声暴露对大鼠行为学及其海马区5－HT1A受体（5－HT1AR）表达的影响,探讨噪声暴露对精神行为的影响及听觉系统与边缘系统的关系。方法将18只健康成年大鼠随机分为对照组和噪声组,每组9只。对照组不予任何处理;噪声组于每天同一时间给予中心频率为4 kHz、声强为100 dB SPL的宽带白噪声持续暴露4小时,共28天。分别于实验前1天和第28天对两组大鼠行ABR检测、糖水偏爱实验、体重和摄食量的检测,于实验前1天、第14天和第28天观察大鼠的旷场行为变化,并于第28天完成ABR测试后,快速分离大鼠海马组织,采用Western －Blot和免疫组化方法检测大鼠海马区5－HT1AR的表达。结果实验前1天两组ABR反应阈、体重及摄食量、糖水偏爱及旷场行为均无差异（ P＞0．05）;实验第28天,噪声组大鼠的 ABR反应阈（69．44±4．97 dB SPL ）较对照组（32．22±2．48 dB SPL ）明显升高（P＜0．05）;噪声组大鼠糖水偏爱程度、体重和摄食量较对照组明显降低,差异有统计学意义（均为 P＜0．05）;实验第14、28天噪声组的旷场行为较对照组明显减少（均为 P＜0．05）;噪声组大鼠海马5－HT1AR的表达较对照组明显降低（P＜0．05）。结论慢性噪声暴露会导致大鼠海马区5－HT1AR表达下降,出现抑郁样行为学表现,提示了听觉系统与边缘系统的相关性。     

长期注射水杨酸钠对大鼠听皮层酪氨酸受体激酶B及c－fos基因表达的影响

目的通过观察长期注射水杨酸钠后大鼠听皮层中酪氨酸受体激酶B(TrkB)及c-fos基因的表达,探讨其在水杨酸钠耳毒性机制中的作用。方法健康成年Wistar大鼠36只,分为正常组(不做任何处理)、慢性组(肌肉注射水杨酸钠175mg/kg,2次/天,时间间隔8小时,连续注射14天)、慢性恢复组(前期处理同慢性组,停药后恢复28天),每组12只。造模结束后各组大鼠均行听性脑干反应(ABR)检测,然后断头处死并迅速取出听皮层,运用实时荧光定量PCR技术及Western-blot技术分别检测三组大鼠听皮层中TrkB及c-fos的表达。结果正常组ABR反应阈为36±2.23dB SPL,慢性组反应阈升高为41.3±3.31dB SPL,与正常组比较,差异有显著统计学意义(P<0.01);慢性恢复组ABR反应阈为38.6±5.51dB SPL,与正常组比较,差异无统计学意义(P>0.05)。慢性组听皮层c-fos mRNA表达为1.24±0.09,蛋白的表达为0.70±0.12,慢性恢复组听皮层c-fos mRNA的表达为1.23±0.04,蛋白的表达为0.68±0.08,两组均高于正常组(分别为1.12±0.05、0.50±0.04),差异有统计学意义(P<0.01)。慢性组听皮层TrkB mRNA表达为1.26±0.10,蛋白的表达为1.85±0.17,慢性恢复组听皮层TrkB mRNA表达为1.23±0.07,蛋白的表达为1.80±0.08,均高于正常组(分别为1.11±0.03,1.53±0.16),差异有统计学意义(P<0.05)。结论长期注射水杨酸钠后大鼠听皮层c-fos基因表达升高,可能与听觉中枢神经活动增强有关;长期注射水杨酸钠可能通过上调大鼠听皮层TrkB的表达,增强听皮层神经营养因子的功能促进听皮层功能重塑。     

鼓室注射地塞米松拮抗顺铂耳毒性的研究

目的：探讨鼓室注射地塞米松对顺铂致听觉损伤的保护作用。方法将55只豚鼠分为4组：正常对照组（I组）10只,腹腔注射生理盐水16 ml／kg;地塞米松组（II组）15只,经鼓室注射地塞米松10 mg／ml;顺铂组（III组）15只,单次腹腔注射顺铂16 mg／kg;顺铂＋地塞米松组（IV组）15只,经鼓室注射地塞米松10 mg／ml ,1小时后腹腔注射顺铂16 mg／kg。给药前及给药后第7天测试各组豚鼠听性脑干反应（auditory brainstem response, ABR）,并检测耳蜗组织丙二醛（malondiadehyde,MDA）含量和超氧化物歧化酶（superoxide dismutase,SOD）活性。结果 I～IV组给药前ABR反应阈分别为28．50±4．74、28．67±5．82、26．67±4．88和27．33±5．30 dB nHL,差异无统计学意义（P＞0．05）;给药后I组和II组ABR反应阈分别为29．00±3．94和31．33±5．81 dB nHL,给药前后差异无统计学意义（P＞0．05）;给药后III组和IV组ABR反应阈为55．33±4．81、40．67±3．72 dB nHL,均显著高于给药前（P＜0．05）,但IV组ABR反应阈低于III组（P＜0．05）。给药后I组 MDA含量和SOD活性分别为2．01±0．07 mmol／L和234．10±13．09 U／ml,II组分别为2．06±0．09 mmol／L和233．20±13．24 U／ml,两组比较差异无统计学意义（P＞0．05）,III、IV组 MDA含量分别为5．74±0．17、3．51±0．18 mmol／L,显著高于I、II 组（均为P＜0．05）,但IV组 MDA含量显著低于 III 组（P＜0．001）;III、IV 组 SOD 活性分别为107．90±14．21、162．70±11．25 U／ml,明显低于I、II组（均为P＜0．05）,但IV组的SOD活性显著高于III组（P＜0．001）。结论鼓室注射地塞米松对顺铂耳毒性具有一定的拮抗作用。     

3～5岁儿童短声听性脑干反应正常值及演化

目的：研究3～5岁正常听力儿童短声听性脑干反应（cABR）的特征及变化趋势。方法将132例（224耳）3～5岁正常听力儿童按年龄（1岁为1组）分为3组：3岁组74耳,4岁组78耳,5岁组72耳,对三组儿童进行短声听性脑干反应检测,对各组 ABR 反应阈、波潜伏期及波间期进行单因素方差分析,之后进行两组间的多重比较。结果80 dB nHL 强度下,3岁组 ABR 波 I、III、V 潜伏期分别为1．24±0．09、3．53±0．16、5．39±0．23 ms,I－III、I－V 波间期分别为2．30±0．15、4．15±0．22 ms,反应阈为22．57±4．40 dB nHL;4岁组波 I、III、V 潜伏期分别为1．23±0．10、3．52±0．39、5．30±0．21 ms,I－III、I－V 波间期分别为2．28±0．39、4．07±0．22 ms,反应阈为21．15±4．83 dB nHL;5岁组波 I、III、V 潜伏期分别为1．24±0．10、3．67±0．63、5．34±0．19 ms,I－III、I－V波间期分别为2．42±0．63、4．09±0．19 ms,反应阈为21．11±3．48 dB nHL。3～5岁儿童 cABR 反应阈均值为21．61±4．33 dB nHL,除4岁组波 V 潜伏期和 I－V 波间期较3岁组缩短,差异有统计学意义外（P ＜0．05）,余两组间差异均无统计学意义。结论3、4、5岁正常听力儿童 ABR 反应阈分别为22．57±4．40、21．15±4．83、21．22±3．48 dB nHL;3～5岁儿童 cABR 的正常反应阈均值为21．61±4．33 dB nHL,听觉脑干中枢可能在4岁发育成熟。     

甲硫氨酸对噪声性听力损失的预防作用研究

目的：探讨口服甲硫氨酸对噪声性听力损失的预防作用。方法将解放军某部健康男性军人203例随机分为试验组（113例）和对照组（90例）,均给予脉冲噪声（峰值160～170 dB SPL）暴露1小时,暴露前3天试验组口服甲硫氨酸片1500 mg/日×3天,对照组则口服等剂量安慰剂（淀粉）。两组受试者噪声暴露前后行纯音测听、听性脑干反应听（ABR）检查,对检查结果进行统计学分析。结果噪声暴露后1天,两组各频率纯音听阈均高于暴露前（P＜0．05或 P＜0．01）,暴露后7天,对照组纯音听阈仍升高（P＜0．05）,而试验组与暴露前比较差异无统计学意义（P＞0．05）;噪声暴露前、暴露后1天、7天,试验组 ABR 反应阈分别为40．5±9．3、51．7±12．3、44．1±11．4 dB nHL,对照组分别为41．5±8．9、62．4±13．7、47．6±12．5 dB nHL,试验组 ABR I－V 波间期分别为3．72±0．21、3．99±0．36、3．82±0．25 ms,对照组分别为3．71±0．22、4．45±0．37、3．85±0．34 ms,噪声暴露后1、7天两组间 ABR 反应阈、I－V 波间期比较差异有统计学意义（P＜0．05或 P＜0．01）。结论噪声暴露前口服甲硫氨酸片能有效减轻噪声暴露后噪声性听力损失的发生。     

脉冲噪声暴露后大鼠频率特异性听性脑干反应变化特点及意义

目的探讨脉冲噪声暴露后不同时间大鼠频率特异性听性脑干反应变化特点及意义。方法成年SD大鼠50只分为5组:正常组及脉冲噪声暴露后3、7、14、28天组,每组10只。脉冲噪声条件为:平均压力峰值为156dBSPL,脉宽0.25ms,暴露50次,分别于暴露前后对大鼠行ABR检测,刺激声为短音(tonepip),频率范围为2～32kHz。结果①正常大鼠2、4、8、16、32kHz的平均听阈分别为68.5±2.67、58.2±2.58、39.3±3.33、37.5±2.95、37.3±3.60dBSPL;②与脉冲噪声暴露前相比较,暴露后各组2、4、8、16、32kHzABR阈值均明显提高,差异有统计学意义(P<0.05),其中高频阈移的幅度较低频阈移幅度大;在暴露后恢复第7天时,各频率ABR阈值有所恢复,第14天时恢复明显,第28天时与第14天接近。结论脉冲噪声暴露后大鼠频率特异性听性脑干反应阈值升高,第7天后开始有所恢复,可为后期进一步研究听觉中枢可塑性建立稳定有效的急性声损伤动物模型。     

模拟中长期微重力和噪声环境对大鼠听功能及内耳毛细胞凋亡的影响

目的 研究模拟中长期微重力和噪声环境对大鼠听功能及内耳细胞凋亡的影响.方法 36只SD大鼠随机分为两组:空白组(6只)和实验组(30只).实验组给予持续尾部悬吊模拟微重力及飞船舱内噪声(稳态噪声+脉冲噪声)暴露,分别于悬吊及暴露前、悬吊及暴露3天、1周、2周、4周和8周后检测双耳ABR反应阈,并于悬吊及暴露3天、1周、2周、4周和8周取实验动物耳蜗行免疫组化染色观察半胱氨酸天冬氨酸蛋白酶3(caspase-3)在内耳的表达.空白组不做任何处理,常规饲养,于实验前及实验3天、1周、2周、4周和8周分别检测双耳ABR反应阈,并于饲养8周后取耳蜗行免疫组化染色观察.结果 实验前两组大鼠ABR反应阈差异无统计学意义(P＞0.05).实验组大鼠悬吊及噪声暴露后各时间点ABR反应阈较空白组均明显增高(P＜0.01),悬吊及暴露4周实验组大鼠ABR反应阈为90.00±4.26 dB SPL,明显高于3天、1周、2周及8周时(P＜0.05);悬吊及暴露8周大鼠ABR反应阈(80.00±5.22 dB SPL)有所下降,与暴露2周(85.00±4.77 dB SPL)、4周大鼠比较差异有统计学意义(P＜0.01).悬吊及噪声暴露后大鼠内耳细胞caspase-3的表达较空白组明显增强,且在一定时间内随暴露时间的延长其表达有逐渐增强的趋势,尤以悬吊及暴露4周时最明显,暴露8周时其表达强度较4周时明显下降.结论 模拟中长期微重力和噪声环境对大鼠的听功能有明显损伤,且与内耳细胞凋亡呈相同的趋势;微重力和噪声因素造成的听功能损伤可能与内耳细胞的凋亡有关.     

Neural Correlates of an Auditory Afterimage in Primary Auditory Cortex

The Zwicker tone (ZT) is defined as an auditory negative afterimage, perceived after the presentation of an appropriate inducer. Typically, a notched noise (NN) with a notch width of 1/2 octave induces a ZT with a pitch falling in the frequency range of the notch. The aim of the present study was to find potential neural correlates of the ZT in the primary auditory cortex of ketamine-anesthetized cats. Responses of multiunits were recorded simultaneously with two 8-electrode arrays during 1 s and over 2 s after the presentation of a white noise (WN) and three NNs differing by the width of the notch, namely, 1/3 octave (NN1), 1/2 octave (NN2), and 2/3 octave (NN3). Both firing rate (FR) and peak cross-correlation coefficient () were evaluated for time windows of 500 ms. The cortical units were grouped according to whether their characteristic frequency (CF) was inside (In neurons) or outside (Out neurons) a 1-octave-wide frequency band centered on the notch center frequency. The ratios between the FRs and the s for each NN and the WN condition and for each group of neurons were then statistically evaluated. The ratios of FRs were significantly increased during and after the presentation of the NN for the In neurons. In contrast, the changes for the Out neurons were small and most often insignificant. The ratios of the values differed significantly from 1 in the In–In and In–Out groups during stimulation as well as after it. We also found that the s of Out neurons were dependent on the type of NN. Potentially, a combination of increased and increased FR might be a neurophysiological correlate of the ZT.     

听神经病谱系障碍儿童的听觉能力

通过对比听神经前反应(耳声发射/耳蜗微音电位)和神经反应(听性脑干反应)的结果来诊断小儿听神经病,已经是一件相对简单的事情.然而,如何评价受累小儿的听觉能力,并据此采取合适的干预策略仍然是一个重大挑战.     

Auditory Neuropathy / Auditory Dyssynchrony in children with Cochlear Implants

The electrical stimulation generated by the Cochlear Implant (CI) may improve the neural synchrony and hence contribute to the development of auditory skills in patients with Auditory Neuropathy / Auditory Dyssynchrony (AN/AD).AimProspective cohort cross-sectional study to evaluate the auditory performance and the characteristics of the electrically evoked compound action potential (ECAP) in 18 children with AN/AD and cochlear implants.Material and methodsThe auditory perception was evaluated by sound field thresholds and speech perception tests. To evaluate ECAP's characteristics, the threshold and amplitude of neural response were evaluated at 80Hz and 35Hz.ResultsNo significant statistical difference was found concerning the development of auditory skills. The ECAP's characteristics differences at 80 and 35Hz stimulation rate were also not statistically significant.ConclusionThe CI was seen as an efficient resource to develop auditory skills in 94% of the AN/ AD patients studied. The auditory perception benefits and the possibility to measure ECAP showed that the electrical stimulation could compensate for the neural dyssynchrony caused by the AN/AD. However, a unique clinical procedure cannot be proposed at this point. Therefore, a careful and complete evaluation of each AN/AD patient before recommending a Cochlear Implant is advised. Clinical Trials: NCT01023932     

听神经科学与听神经病的认识

1996年,Starr将具有"听性脑干反应不能引出或严重异常,耳声发射能引出,言语识别率相对听力不成比例下降"等特殊临床表现的一组听力障碍患者,命名为"听神经病(auditory neuropathy,AN)",受到医学界的广泛关注。10多年来,从基础研究到临床研究,国内外对该病的认识不断加深。2008年6月,意大利科莫举行的国际新生儿听力筛查会上,美国科罗拉多州儿童医院的Deborah Hayes教授组织专家对该病进行了热烈讨论,专家们一致认为将听神经病改称为听神经病谱系障碍(auditory neuropathy spectrum disorder,ANSD)更能代表本病的特征。会后Deborah Hayes教授组织专家们编写和出版了《婴幼儿听神经病谱系障碍诊疗指南》一书,书中还编入了专家们从不同角度对该病认识的阐述。为了让大家能够更深入细致地了解婴幼儿听神经病,规范我国婴幼儿听神经病的诊疗工作,经与DeborahHayes教授协商,该书的翻译和出版权被授予首都医科大学附属北京同仁医院和北京市耳鼻咽喉科研究所,由中华医学会耳鼻咽喉头颈外科学分会听力学组组织有关专家对指南进行了翻译。现将《婴幼儿听神经病谱系障碍诊疗指南》翻译稿刊登于《听力学及言语疾病杂志》。在指南的翻译过程中,得到了倪道凤、卜行宽和李兴启等教授的大力支持和指导,参与此项工作的中华医学会耳鼻咽喉头颈外科学分会听力学组的同仁们尽心尽力,付出了大量的辛勤劳动,指南的翻译和审校工作得到了武汉大学人民医院吴展元教授耐心和细致的指导,在此一并表示感谢!     

生长相关蛋白-43在听觉剥夺大鼠听皮层中的表达研究

目的探索听觉系统发育和损伤后修复的神经可塑性的分子机制,探索GAP-43与幼鼠听皮层发育和可塑性的关系;方法应用免疫组织化学方法,检测正常幼鼠(3周龄、4周龄及8周龄大鼠)及耳毒性药物致聋鼠发育的不同阶段(2周2天龄大鼠氨基糖苷类抗生素致聋后5天、12天及40天,即致聋的3周龄、4周龄及8周龄大鼠)GAP-43在听皮层的阳性神经元表达变化;结果发现GAP-43在刚出生大鼠听皮层阳性神经元高表达,随发育表达逐渐降低,出生后3周(NC P3W)的大鼠听皮层平均每高倍视野阳性神经元数为111.50±4.90,出生后4周(NC P4W)为84.17±3.24,出生后8周(NC P8W)为66.67±4.17;耳蜗损伤后早期GAP-43在幼鼠听皮层的表达反应性升高;结论 GAP-43与幼鼠听皮层发育和可塑性密切相关,GAP-43可作为听皮层乃至听觉系统发育和可塑性的重要标志。     

Auditory Neuropathy in Children

Auditory neuropathy is a sensorineural disorder characterized by absent or abnormal auditory brainstem evoked potentials and normal cochlear outer hair cell function. A variety of processes is thought to be involved in its pathophysiology and their influence on hearing may be different. We present here the diagnostic sequence and management of two new cases of auditory neuropathy in breastfeeding children.     

Auditory Dysfunction in Stroke

The auditory and vestibular systems share the same end organ and cranial nerve, yet vestibular signs and symptoms are common with stroke, whereas hearing disturbances are much less frequent. Several reasons would appear to account for this striking dissimilarity. One is that the auditory pathway is less ubiquitous than the vestibular pathways. The likelihood that a stroke involves the auditory pathway is, therefore, less on this basis alone. A second difference, to our knowledge not previously reported, is that the auditory pathway is often spared by the most common strokes. This is because major parts of the auditory pathway, such as the cochlear nucleus, inferior colliculus and medial geniculate body, have multiple sources of blood supply. A third well-recognized factor is the redundancy of the central auditory system and its strong bilateral representation above the level of the cochlear nuclei. Consequently, rostral to the cochlear nuclei gross deficits in hearing, such as those measured by standard pure-tone audiometry and speech discrimination, only occur if lesions are bilateral. Furthermore, widespread bilateral lesions of the auditory system typically render the patient unable to respond or are incompatible with life. In contrast, language disorders are more frequent because language is usually unilaterally represented in the cortex. Certainly, cerebral stroke often includes the auditory system, resulting in various types of auditory disorders, but most hemispherical lesions produce subtle hearing dysfunctions that can only be detected with sophisticated psychoacoustic and electrophysiological testing. The purpose of this review is to provide an overview of the auditory system and its blood supply and to review how auditory processing can be affected by stroke. Psychoacoustic and electrophysiological test procedures for identifying lesions in the central auditory system are described. The literature of hearing disorders due to stroke is reviewed and illustrative cases are presented.     

Auditory neuropathies in infants

Auditory neuropathy is a sensorineural disorder characterized by absent or abnormal auditory evoked potentials, and normal cochlear outer hair cell function. It is believed that a variety of processes are involved in its pathophysiology and their influence on hearing can differ. We describe the diagnostic sequence and management of two new cases of auditory neuropathy in infants. The first case was a girl with no risk factors for hearing loss. Her absence of response to sounds was compared with her twin's reactions. Otoacoustic emissions were present but no auditory evoked potential response was detected. Her evolution was characteristic of deep sensorineural hearing loss without a hearing aid. At present she is awaiting a cochlear implant. The second case was a boy who underwent hearing loss screening for hyperbilirubinemia. Examinations were repeated three months later because the mother suspected hearing loss. Objective tests showed a pattern of auditory neuropathy. The boy's evolution was different: in spite of the presence of destructured auditory evoked potentials; it was evident that the boy conserved some hearing and had thresholds suggestive of moderate hearing loss.