豚鼠内耳手术对脑干诱发电位测定的影响

Effect of inner ear surgery on ABR measurement in guinea pigs

目的 探讨豚鼠内耳手术对脑干诱发电位 (ABR)测定的影响。方法 Hartley系豚鼠 ,18只 ,体重2 5 0～ 30 0 g。全麻后取耳后切口行鼓泡开放 ,暴露耳蜗。在手术显微镜下经耳蜗微孔 (直径 30 μm)将不同的溶液PBS、钥孔戚血蓝素 (Keyholelimpethemocyanin ,KLH)、氨甲喋呤 (methotrexate ,MTX)及 2 0ml的MTX (10ml)和KLH (10ml)混合制剂分别导入鼓阶。按以下程序测定ABR ,即第 1天 (系统免疫前 ) ,手术前 5min(第 14天 ) ,手术后 5min及 1周或 2周。结果 共测定 18只 36耳 ,其中 32耳手术前后听力损失为 0～ 5dB ,4耳听力损失较为严重 ,(手术前后测定听力损失超过 4 5dB) ,且术后 1周或 2周未恢复 ;在听力损失较轻 ,手术前后测定听力损失小于 2 0dB的另外 4耳中 ,术后 1周或 2周ABR恢复至正常。结论 为正确评估豚鼠ABR ,除外手术对ABR测定的影响 ,内耳开窗术或任何其他有可能损伤耳蜗功能的操作 ,都应于操作结束后即刻测定ABR。

Objective Guinea pig is an ideal animal for hearing research, but few literature relates to the effect of inner ear surgery on ABR measurement. Methods In this study, Eighteen female Hartley guinea pigs (weighing 250～300 g) were used to investigate the effect of cochleostomy on ABR. After general anesthesia, cochlea of guinea pig was exposed through a post-auricular incision. Different solutions (PBS, antigen and methotrexate) were infused into the scalae tympani through a microhole (30 μm in diameter). ABR was measured in each animal according to the following program, i.e., either on day one (before systemic immunization), or 5 minutes pre-operation (day 14), 5 minutes post-operation and one or two week after surgery. Results In 36 ears (18 guinea pigs) measured, only four ears showed severe hearing loss (over 45 dB before and after the surgery), with no improvement in one week or two weeks after surgery. In another four ears with minimal hearing loss (less than 20 dB), ABR returned to normal level in one week or two weeks after surgery. Conclusion To exclude the surgical effect on hearing threshold level in guinea pigs, instant ABR measurement is highlighted following cochleostomy or other procedures that might damage the cochlear functions.