脑干诱发电位及其应用

Brainstem evoked potential and its application

目的:分析脑干诱发电位的波形特点,观察正常气骨导脑干诱发电位Ⅴ波潜伏期-强度函数曲线及其相应的反应阈值的变化,为临床气导脑干诱发电位和骨导脑干诱发电位的联合应用提供参考依据。方法:实验于2005-03/08在解放军广州军区武汉总医院听力中心完成。选取听力正常的青年大学生28例(56耳),纯音听阈测试各频率气导听阈均≤15dBHL,所有受试者外耳及中耳均无异常,无噪声暴露史、使用耳毒药物及神经科疾病史。①纯音听阈测试:首先测试1000Hz的听阈,给声长度0.5～1.0s,给声间隔不短于1s,避免节律给声,从40dBHL开始测试。听阈的搜寻遵循“减十加五”的原则,即受试者若能听到声音,则将声强减少10dB;若不能听到,则增加5dB。测得1000Hz的听阈后,按2000,3000,4000,6000,8000,1000,500,250Hz先高频后低频的顺序检测,其中1000Hz给予重复测试,用于检测受试者在熟悉过程后测得的听阈的可重复性。②脑干诱发电位测试:采用Nicolet-spirit型诱发电位仪记录脑干诱发电位波形。刺激声采用短声,声刺激重复率为21.1次/s,正负交替刺激极性,扫描时间15ms,滤波范围50～2500Hz,平均叠加1000次。以10dB逐档降至无反应波形出现时再上升5dB,观察可重复出现反应的最低强度作为脑干诱发电位反应阈。并观察对侧给予白噪声掩蔽后骨导脑干诱发电位阈值及潜伏期的变化。结果:按意向处理分析,实验选取听力正常的28例青年大学生全部进入结果分析。①骨导脑干诱发电位波形描述:骨导脑干诱发电位在其最大输出强度(100dBpeSPL)下诱发的波形仅引出明显的Ⅰ波和Ⅴ波,且重复性强,无明显起始音伪迹。与气导脑干诱发电位同等强度波形相比非常相似,但气导脑干诱发电位波形波幅较大,且引出Ⅲ波。②脑干诱发电位Ⅴ波潜伏期强度函数曲线:随着刺激强度逐渐减低,潜伏期均逐渐渐延长,但骨导Click的潜伏期要比气导延长程度大些。③气导与骨导脑干诱发电位反应阈的比较:气导脑干诱发电位Ⅴ波阈值明显低于骨导[(45.09±2.23),(61.25±2.18)dBpeSPL,P<0.01]。④对侧给声掩蔽对骨导脑干诱发电位的影响:对侧白噪声给声强度在70dBpeSPL以下时对骨导脑干诱发电位阈值及阈上10dB强度下波Ⅴ潜伏期均无明显影响(P>0.05)。结论:气、骨导脑干诱发电位波形特点极为相似,骨导脑干诱发电位检测在方法学上能与气导脑干诱发电位相补充,联合使用可望用于传导障碍及其程度的评估。此外骨导脑干诱发电位测试时应常规加对侧噪声掩蔽,但掩蔽声强度不应超过60dB。

AIM： To analyze the wave characteristics of brainstem evoked potential （BEP）, observe normative BEP V wave latency-intensity function curve and changes of corresponding threshold, and provide the reference for the combined application of air-conduction and bone-conduction BEP in clinic. METHODS： The experiment was carried out at the Auditory Center, Wuhan General Hospital of Guangzhou Military Area Command of PLA between March and August 2005. Totally 28 youth undergraduates （56 ears） with normal hearing were selected to conduct the pure tone threshold audiometry （PTA）, and the air-conduction auditory threshold of each frequency was no more than 15 dBHL. All the testees were found normal in external ear and middle ear, without noise exposure, ototoxic drugs application or neurological history.①PTA： Firstly, with the voice length of 0.5-1.0 seconds and interval of more than 1 seconds, the auditory threshold of 1 000 Hz was measured in avoidance of rhythm voice from 40 dBHL on. According to the principle of decreasing 10 or increasing 5, the sound intensity was decreased 10 dB if testee could hear, whereas increased 5 dB if could not hear. Then the testees were detected from high frequency to low frequency （2 000, 3 000, 4 000, 6 000, 8 000, 1 000, 500, 250 Hz）, and repoatedly in 1 000 Hz to assay the reproducibility.②BEP： Nicolet-spirit evoked potential apparatus was applied to record BEP wave. With the repetitive rate of 21.1 times per second, the stimulation sound was short sound in the alternation of positive and negative electrode, and scanned for 15 ms in filter-wave range of 50-2 500 Hz, averagely repeated for 1 000 times. The lowest intensity at which response occurred repeatedly was defined as response threshold of BEP, meanwhile, the changes of bong-conduction BEP threshold and latency were observed after white noise masking. RESULTS： According to the intention-treat analysis, 28 youth undergraduates were all involved in the result analysis. （!）Deacription of bone-conduction BEP wave： The air-conduction and bone-conduction wave educed obvious Ⅰ wave and V wave repeatedly without obvious false traces of initial sound. Moreover, the air-conduction BEP wave exhibited wider amplitude and educedⅢ wave. ②BEP V wave latency-intensity function curve： The latency prolonged gradually with the decrease of stimulation intensity. The bone-conducted clicks yielded somewhat longer latencies than air-conducted clicks.③Comparison of BEP response threshold between air-conduction and bone-conduction： The threshold of air-conduction was significantly lower than that of bone-conduction [（45.09±2.23）, （61.25±2.18） dBPOSPL, P 〈 0.01]. ④Influence of contralateral masking on bone-conduction BEP： There was no remarkable influence of contralateral white noise of less than 70 dBpeSPL intensity on the bone-conduction BEP threshold and of suprethreshold 10 dB intensity on the latency of V wave （P 〉 0.05）. CONCLUSION： The waves of air-conduction and bone-conduction BEP are similar in the wave characteristics, and complementary in methodology, thus the combined application of two conductions is hopeful to apply on the evaluation of conductive disorder and its level. In addition, contralateral noise masking is necessary when administering bone-conduction BEP test within 60 dB SPL intensity.