听觉传导通路不同部位的病变对中枢掩蔽的影响

目的了解听觉传导通路不同部位的病变对中枢掩蔽的影响，为临床分析掩蔽测试结果提供参考。方法分别对一侧耳正常另一侧耳为传导性聋的患者30例(外伤性鼓膜穿孔、分泌性中耳炎及慢性化脓性中耳炎各10例)、耳蜗性聋患者27例(突聋伴眩晕7例、突聋不伴眩晕及原因不明各10例)、蜗后性聋患者7例(单侧听神经瘤3例，单侧听神经病4例)进行中枢掩蔽测试。结果外伤性鼓膜穿孔10耳中枢掩蔽接近正常；分泌性中耳炎及慢性化脓性中耳炎中枢掩蔽有不同程度的降低。突聋合并眩晕耳，中枢掩蔽效应高于正常耳10dB以上，且有极大的个体差异；而在其他耳蜗病变耳，中枢掩蔽幅值明显低于正常耳。蜗后病变耳中枢掩蔽表现也各异。结论在中耳病变耳，当对侧掩蔽声达40dBEM时，中枢掩蔽效应大于5dB，故如掩蔽测试时所用掩蔽声大于40dBEM则需对测试结果进行修正。在突聋伴眩晕耳，因中枢掩蔽效应幅值极大，故测试气导听阈时，应尽可能用插入式耳机，骨导测试应放弃。在蜗后病变耳应根据具体情况拟定掩蔽方案。

Pathology in Different Sites of Auditory Pathway had Different Effects on the Central Masking

Objective To investigate the appropri ate changes of the central masking effect(CME) when there were pathologies in d ifferent segment of auditory pathway,so as to give some instructions in cli nical masking test. Methods We tested the subjects with one ear normal and th e other ear diseased. The diseased ears included conductive deafness in 30 ca ses?sensory deafness in 27 cases and retrocochlear deafness in 7 cases. Results The pure conductive deafness had very little effect on CME; secretory otistis media and chronic suppurative otistis medi a made CME lower than normal due to the secondary cochlear impairment .When su dden deafness companied with vertigo,CME appeared much higher than the normal and appeared great difference individually;but CME appeared lower than normal at other kinds of cochlear deafness ears.CME appeared differently at retrocochlear deafness ears. Conclusion Audiometry results should be corrected when th e masker higher than 40 dB EM,because the masker can make the CME higher than 5 dB in the conductive impairment ears.In the sudden de afness companied with vertigo ears,CMEs were too high and too individually to fi nd a suitable correction for PTT.Insert earphone should be used in measuring the air-conduction PTT,and bone-conduction PTT test might be given up.