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目的 通过记录电刺激诱发听觉脑干电位(EABR)阈值变化搞清楚内耳外淋巴“枯竭”状态对听神经兴奋性影响。方法 在手术显微镜帮助下,小心把标准刺激电极沿蜗轴插入鼓阶约4mm,用压碎的肌肉轻轻封住圆窗口。然后用波宽为50μs/phase、刺激速率为30次/秒电荷平衡双相脉冲电流刺激受试动物鼓阶内的靠近蜗尖的电极对(1/2),记录两次EABR阈值,取均值。然后把明胶海绵做成直径约为1mm,长约为4cm小的圆柱形,把一端放入前庭阶持续吸干外淋巴,直到显微镜下见鼓阶外淋巴消失,模拟外淋巴“枯竭”状,用以上电刺激参数再次记录电极对(1/2)的EABR阈值两次,取均值。比较前后两次EABR阈值的变化(t检验)。结果 耳蜗外淋巴“枯竭”状态时测试到的EABABR阈值0.63±0.11mA较充满外淋巴时0.27±0.08mA明显升高(P<0.001)。结论 EABR阈值升高说明耳蜗鼓阶外淋巴呈现“枯竭”状态时听神经兴奋性明显下降,临床上少数重聋或者全聋患者耳蜗外淋巴呈现“枯竭”状态,推测其电子耳蜗植入临床效果可能较耳蜗鼓阶内外淋巴正常患者差。
OBJECTIVE: To investigate the effect of auditory nerve excitability on the auditory brainstem response (EABR) threshold induced by electrical stimulation in the “exhausted” state of the inner ear. Methods With the help of a surgical microscope, carefully insert the standard stimulation electrode approximately 4 mm into the tympanum along the worm shaft and gently seal the circular window with the crushed muscles. The Eppendorf’s electrode pair (½) was then stimulated by a biphasic pulse current with a wave width of 50μs / phase and a stimulation rate of 30 beats / second. The EABR threshold was recorded twice and the mean . Then gelatin sponge made into a diameter of about 1mm, about 4cm small cylindrical, put one end into the vestibule continued suck the perilymph, until under the microscope see the tympanic lymph disappeared, simulate the perilymph “dead” shape, The EABR threshold of the electrode pair (1/2) was again recorded twice with the above electrical stimulation parameters, taking the mean. The EABR threshold changes (t-test) were compared twice before and after. Results EABABR threshold of 0.63 ± 0.11 mA was significantly higher than that of eosinophils (0.27 ± 0.08 mA) when perfused with “extranodal” cochlea (P <0.001). Conclusions The increased threshold of EABR indicates that the excitability of auditory nerve in the epicardial lymphatic of the cochlear is significantly decreased. In clinical practice, a small number of deaf or all-deaf patients show cochlear extra-parodial lymphadenectasis, suggesting that the cochlear implants may have clinical effects Worse than the normal cochlear drum outside the normal lymph nodes.