Nd:YAG激光照射鼓膜对听觉功能影响的实验研究

目的 :探讨不同功率Nd :YAG激光照射鼓膜对内耳结构和功能的影响。方法 :应用光纤末端功率为 8W、6W、4W的Nd :YAG激光针对豚鼠作鼓膜照射 2s。采用听性脑干反应、耳蜗基底膜铺片及扫描电镜技术 ,观察激光照射前后 (分即刻及饲养 2周后 )ABR阈值及形态学变化。结果 :所用激光功率与内耳损伤程度成正相关 ,3组ABR阈值在即刻和饲养 2周后均升高 ,8W、6W组均较 4W组升高明显 ,8W、6W组照射后 2周ABR阈值较照射前差异有显著性 (P <0 .0 5 ) ,但 4W组 2周后恢复明显 ,与照射前差异无显著性。照射后立即取材的耳蜗毛细胞形态改变的结果 :即刻 8W、6W组耳蜗外毛细胞出现肿胀 ,硝酸银浓染 ,血管纹血管扩张 ,4W组无明显改变。饲养 2周后 ,8W组外毛细胞平均损失达 45 % ,6W组平均损失 2 0 % ,以上两组内毛细胞亦有少量缺失 ,4W组内、外毛细胞形态基本正常。结论 :本实验提示 :采用Nd :YAG激光治疗中耳疾病时 ,其光纤末端输出功率应控制在 4W ,时间为 2s为宜 ,否则可能会导致不可逆的听力下降。

An Experimental Study of the Effects of Nd:YAG Laser Irradiation of Tympanic Membrane on Inner Ear

Objective:To explore the effects of Nd:YAG laser irradiation of tympanic membrane on the structure and function of inner ear. Methods:Three output powers of 8 W,6 W and 4 W were respectively used to irradiate the tympanic membrane of guinea pigs for 2 seconds, and the guinea pigs were divided into 3 groups(8 W,6 W and 4 W).The ABR thresholds were measured before, immediately after and two weeks after irradiation.Cochlear preparation, cochlear section and scanning electron microscope were applied to observe the morphological alteration. Results:The experiment elucidated that the impairment of inner ear was correlated with the laser output power. Immediately after irradiation, swelling and strong staining of outer hair cells and stria vascularis dilation were present in cochlea of group 8 W and group 6 W without obvious injury in group 4 W. Two weeks later, the outer hair cells loss rates were 45% and 20% in group 8 W and group 6 W.There was also some loss in inner hair cells. The hair cells of group 4 W were normal. The thresholds of ABR were elevated in group 8 W and group 6 W after irradiation. There were significant differences before and after irradiation in group 8 W and group 6 W (P<0.05).But there were no significant differences in group 4 W. Conclusion:In the Nd:YAG laser treatment of middle ear disease, to protect inner hair cell function, the appropriate output power and irradiation duration are 4 W and 2 seconds.