BASIC AND CLINICAL RESEARCH ON MECHANISMS OF TINNITUS IN ACOUSTIC

为了阐明听神经瘤耳鸣的机制，我们研究了反映耳蜗微力学的瞬态诱发耳声发射（teoae），该发射与耳蜗外毛细胞的主动运动特性有关。耳蜗传出神经系统包括外毛细胞的功能障碍被认为是耳鸣的机制之一。我们记录了95例听神经瘤患者和50例梅尼埃病患者的teoae作为对照，以明确耳蜗和耳蜗后听力障碍患者的听力水平与teoae的关系。可获得teoae的听神经瘤患者平均听力水平为28.4(]SY.+- . [)14.6dB，梅尼埃病患者平均听力水平为28.3(]SY.+- . [)12.5dB。虽然有3例听神经瘤患者听力损失超过60 dB，但与健康侧耳相比，TEP （TEOAE参数之一）有所恶化。根据这些结果，我们得出结论：几乎所有听神经瘤患者都对耳蜗有影响。因此，在中重度听力损伤的听神经瘤患者中，正常的teoae似乎并不常见。我们还对听神经瘤中耳鸣的性质进行了研究。本文对85例单侧听神经瘤行保听手术（颅中窝入路或ⅲ型颅中窝扩展入路）的患者进行术前和术后耳鸣的分析。其中37例听力保存成功，48例听力丧失。听力保留组与听力丧失组在耳鸣改善或恶化方面无明显差异。听神经瘤患者对耳鸣性质的主观表现各不相同，因此认为很难推测耳鸣的预后，但两种情况下听神经瘤患者的耳鸣多为轻度，对其生活质量影响不大。少

In order to clarity the mechanisms of tinnitus in acoustic neuroma, we investigated the transient evoked otoacoustic emissions (TEOAEs) which reflect the cochlear micromechanics related to the active motile property of outer hair cells. Dysfunctions of the cochlear efferent nervous system including the outer hair cells have been postulated as one of the mechanisms of tinnitus. We recorded TEOAEs in 95 acoustic neuroma patients and 50 Meniere's disease patients as controls in order to clarify the relationship between the hearing level and TEOAEs in cochlear and retrocochlear hearing impairments. Mean hearing level of the acoustic neuroma patients whose TEOAEs could be obtained was 28.4(]SY.+-。[)14.6dB and that of the Meniere's disease patients was 28.3(]SY.+-。[)12.5dB.Although there were 3 acoustic neuroma patients with TEOAE in spite of hearing impairment over 60 dB,deterioration in TEP (one of the TEOAE parameter) was found compaing with healthy side ear. From these results, we conclu … More ded that there must be an affection to the cochlea in almost all acoustic neuroma patients. Thus, the normal TEOAEs seem to be uncommon in the acoustic neuroma patients with mederate or severe hearing impairment.We also conducted the study on the nature of tinnitus in acoustic neuroma. A series of 85 patients who had undergone hearing-preserved operation (the middle cranial fossa approach or the extended middle cranial fossa approach type III) of a unilateral acoustic neuroma was analyzed about pre and postoperative tinnitus. They consisted of 37 successful hearing-preserved cases and 48 hearing-loss cases. Obvious differences between hearing-preserved cases and hearing-loss cases were not found about improvement or worse of their tinnitus. Subjective expressions of tinnitus nature among acoustic neuroma patients were various, therefore, it was thought that a speculation about prognosis of tinnitus will be difficult, but tinnitus of acoustic neuroma patients in both cases was mostly mild and not so painful for their quality of life. Less