实验性膜迷路积水不同时期耳蜗电活动的变化

Observation on cochlear electrical activities in vivo in different stages of experimental endolymphatic hydrops in guinea pigs

目的:观察实验性膜迷路积水后耳蜗电活动的变化,探讨膜迷路积水后耳蜗的病理生理变化特点。方法:应用微电极技术,通过阻塞豚鼠内淋巴囊及内林巴管,造成膜迷路积水。将动物随机分为3组,每组7只动物,分别于积水1、2、3个月,在耳蜗第三回中阶分别记录0.5 kHz、1 kHz、2 kHz、4 kHz、6 kHz的豚鼠耳蜗内淋巴电位(Edocochlear Potential,EP),微音电位(Cochlear Microphone,CM),总和电位(Summating Potential,SP)和复合动作电位(Compound Action Potential,CAP)。结果:膜迷路积水后,各频率的CM均受到明显抑制,主要以低频为重。随积水时间延长,高频受抑制程度加重。这和临床上梅尼埃氏病的听力变化特点一致。膜迷路积水1、2、3个月,EP分别下降12 mV、21 mV及34 mV,EP下降和积水时间相关(P<0.01)。膜迷路积水后CAP阈移,积水1、2、3个月,CAP分别阈移5.7dB,12.9dB和22.1dB。积水后SP幅度减少,但SP变化的个体差异大。结论:膜迷路积水后,耳蜗电活动受到抑制,并且随积水时间延长而加重。造成此结果的病理因素可能和膜迷路积水后血管纹血流下降及内淋巴电解质紊乱有关。

Objective: To observe the changes in cochlear electrical activities in vivo in experimental endolymphatic hydrops, and to explore its the physiopathologic characteristics. Methods: 30 guinea pigs were used for a model of endolymphatic hydrops by obliterating the endolymphatic sac and duct. The cochlear electrical activities (EP. CM. CAP and SP) were measured with a microelectrode through the spiral ligament of the third turn. Results: The maximum CM output stimulated by pure tone at five frequencies (0. 5, 1, 2, 4 and 6kHz)was reduced in 1, 2 and 3 months after operation. CM was suppressed mainly in low frequencies after one month of hydrops. But the suppression in high frequencies were gradualy severely suppressed after two and three months of hydrops. EP decreased by 12, 21 and 34 mV, respectively, after 1, 2 and 3months of hydrops. The reduction of EP was related well with the duration of hydrops(P<0.01). The present study discovered that CAP threshold shifted by 5.7, 12.9 and 22.1 dB after 1, 2 and 3 months of hydrops. Conclusion: All the amptitudes of cochlear eletrical activities in hydropic ears were decreased. It may be mainly due to blood flow reduction of stria vascularis vessels and electrolyte disturbance in the endolymph.