小儿蜗后听觉神经损害的临床与听力学特征及定位

目的 探讨包含了听神经病在内的ABR严重异常、DPOAE正常为特征的蜗后听觉神经功能障碍小儿的临床与听力学特征及其可能的病损部位.方法 选取2002至2006年听力专科中ABR严重异常、DPOAE正常,排除中耳传导功能异常的患儿86例(165耳),年龄8 d～7岁,平均1岁1个月,入选为本研究对象.选择ABR严重异常、DPOAE异常、排除中耳病变的听功能障碍26例(29耳)患儿作为蜗性病变对照组,选择健康同龄儿童86例(166耳)作为正常对照组,比较蜗后病变、蜗性病变、正常听力3组间ABR波Ⅰ、波Ⅲ、波Ⅴ潜伏期和振幅,以及Ⅰ～Ⅲ波间期等参数的异同.所有数据采用SPSS11.0统计软件包进行t检验.结果 86例蜗后听神经损害患儿中,51例(59.3%)的病例新生儿期有高胆红素血症史,其中40例血中间接胆红素水平达重度标准,11例为轻中度;在首次就诊的原因中,主诉运动障碍者40例(46.5%),听力言语障碍者10例(11.6%);在伴随的疾病中,32例(37.2%)确诊伴随有脑性瘫痪.在86例165耳蜗后听觉神经功能障碍患耳中,103耳最大强度声刺激(103 dB)ABR无波分化,27耳仅见波Ⅰ分化,19耳仅见波Ⅴ分化,13耳见波Ⅰ+Ⅲ分化,3耳见波Ⅰ+Ⅴ分化.仅见波Ⅰ分化耳,其波Ⅰ潜伏期较正常听力耳延长,振幅较正常听力耳低矮(t值分别为-6.75和2.58,P值均<0.05);有波Ⅰ+Ⅲ分化耳,波Ⅰ潜伏期和振幅与正常听力耳差异无统计学意义,波Ⅲ潜伏期则较正常听力耳延长,振幅较正常听力耳低矮(t值分别为-2.77和3.63,P值均<0.05),Ⅰ～Ⅲ波间期较正常听力耳Ⅰ～Ⅲ波间期延长(t=-2.99,P<0.05).结论 在蜗后听觉神经功能损害类型中,最常见的类型为ABR从波Ⅰ开始就严重异常,即听神经病,其病变主要在第Ⅷ颅神经听支;仅见波Ⅰ分化耳,其病变部位主要在第Ⅷ颅神经听支以后;ABR有波Ⅰ+波Ⅲ分化耳,主要病变部位在波Ⅲ的发源神经核团,即上橄榄核以后的听觉神经通路.振幅低矮的波Ⅴ不是听神经病独有的特征.高胆红素血症导致的蜗后听觉神经系统病变的病例中,其受侵害部位的先后次序可能为大脑皮层、腩干听觉神经核团、第Ⅷ对颅神经听支.

Audiological characteristics and localization of lesions in children with retrocochlear auditory nerve impairment

OBJECTIVE: To explore the clinic characteristics, audiological characteristics and location of lesions in children with retrocochlear auditory nerve impairment which, including auditory neuropathy characterized by severely abnormal results of ABR and normal results of DPOAE. METHODS: Between 2002 and 2006, eighty-six cases (165 ears) with severely abnormal ABR but normal results of DPOAE were enrolled in the study group. The mean patient age was one year and one-month-old, with a range of 8 days to 7 years. The cases with abnormal conductive function were excluded. The cases with severely abnormal ABR and normal cochlear functions as measured by DPOAE and without abnormal conductive function were selected as the cochlear lesion group. Some same age healthy children without hearing loss were subjected as normal control group. The latency and amplitude of waves I, III and V, the inter peak latency I-III was compared among the three group. RESULTS: (1) Fifty-one cases (59.3%) had a history of hypercholesterolemia during neonatal period, but 40 cases (46.51%) had a severe hypercholesterolemia and 11 cases (12.79%) had mild or moderate hypercholesterolemia. Clinical features common among the population included a history of dyskinesia [n = 40 (46.51%)], hearing and language disorder [n = 10 (11. 63%)]. Thirty-two cases (37.2%) were accompanied by cerebral palsy . (2) Among the 165 ears, absent ABRs to click stimuli presented at 103 dB was in 103 ears, only wave I was developed in 27 ears and only wave Vwas developed in 19 ears,wave I and III in 13 ears and differentiated wave I and V in 3 ears. (3) When compared to control group, the latency of wave I was prolonged and amplitude of wave I was lower in cases with only wave I developed (t = -6.75 and 2.58, P < 0.05). For for cases with only wave I and III differentiated, the latency and amplitude of wave I was the same but the latency of wave III was prolonged and amplitude of wave III was lower while interpeak latency I-III was prolonged. CONCLUSIONS: Auditory neuropathy which was characterized by severely abnormal ABR was the most common type of retrocochlear auditory nerve impairment. It was mainly due to a disorder of VIII nerve. The pathologies that affect higher levels of the auditory pathway, from the brainstem to the auditory cortex, might be the main sites of lesion in cases with only wave I developed. Superior olivary nucleus where wave III was generated and higher levels of the auditory pathway might be the main sites of lesion in cases with wave I and III differentiated. The low-amplitude wave V was not characteristics of auditory neuropathy. Cerebral cortex, brain stem auditory nucleus and VIII nerve might be damaged successively in cases with retrocochlear auditory nerve impairment induced by hypercholesterolemia.