Levine R A, Gardner J C, Fullerton B C, Stufflebeam S M, Furst M, Rosen B R
Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston 02114.
Brain. 1994 Oct;117 ( Pt 5):1127-41. doi: 10.1093/brain/117.5.1127.
To understand the relationship between brainstem lesions and auditory neurology in patients with multiple sclerosis, we compared behavioural, electrophysiological and imaging data in 38 patients with probable or definite multiple sclerosis and normal or near normal hearing. Behavioural measures included (i) general hearing tests (audiogram, speech discrimination) and (ii) hearing tests likely to be critically dependent upon brainstem processing (masking level difference, interaural time and level discrimination). Brainstem auditory evoked potentials provided the electrophysiological data. Multiplanar high-resolution MRI of the brainstem provided the anatomical data. Interaural time discrimination for high-frequency sounds was by far the most sensitive of all tests with abnormalities in 71% of all subjects. Whenever any other test was abnormal this test was always abnormal. Interaural time discrimination for low-frequency sounds and evoked potentials were closely related and next most sensitive with abnormalities in approximately 40% of all subjects. Interaural level discrimination and masking level difference were least sensitive with abnormalities in < 10% of subjects. Speech discrimination scores correlated significantly with the masking level differences, as well as with interaural time discrimination for high-frequency sounds. Pontine lesions were found in five of the 16 patients, in whom an objective method for detecting magnetic resonance lesions could be applied. All four with lesions involving the pontine auditory pathway had marked abnormalities in interaural time discrimination and evoked potentials. None of the other 12 had evoked potentials abnormalities. We conclude that neurological tests requiring precise neural timing can reveal behavioural deficits for multiple sclerosis lesions of the auditory pons that are otherwise 'silent'. Of all neurological systems the auditory system at the level of the pons is probably the most sensitive to multiple sclerosis lesions, because of its exceptional dependence upon neural timing in the microsecond range and the lack of redundancy in the encoding of high-frequency sounds. Precise neural timing may be critical for some aspects of speech processing.
为了解多发性硬化症患者脑干病变与听觉神经病学之间的关系，我们比较了38例可能或确诊为多发性硬化症且听力正常或接近正常的患者的行为、电生理和影像学数据。行为测量包括：（i）一般听力测试（听力图、言语辨别）和（ii）可能严重依赖脑干处理的听力测试（掩蔽级差、双耳时间和强度辨别）。脑干听觉诱发电位提供电生理数据。脑干的多平面高分辨率MRI提供解剖学数据。高频声音的双耳时间辨别是所有测试中最敏感的，所有受试者中有71%出现异常。每当任何其他测试异常时，该测试总是异常。低频声音的双耳时间辨别与诱发电位密切相关，其次是最敏感的，所有受试者中有约40%出现异常。双耳强度辨别和掩蔽级差最不敏感，受试者中异常率<10%。言语辨别分数与掩蔽级差以及高频声音的双耳时间辨别显著相关。在16例患者中有5例发现脑桥病变，其中可以应用一种检测磁共振病变的客观方法。所有4例病变累及脑桥听觉通路的患者在双耳时间辨别和诱发电位方面均有明显异常。其他12例均无诱发电位异常。我们得出结论，需要精确神经定时的神经学测试可以揭示听觉脑桥多发性硬化症病变的行为缺陷，而这些病变在其他情况下是“无症状的”。在所有神经系统中，脑桥水平的听觉系统可能对多发性硬化症病变最敏感，因为它特别依赖于微秒范围内的神经定时，并且高频声音编码缺乏冗余。精确的神经定时可能对言语处理的某些方面至关重要。
