Starr A, McPherson D, Patterson J, Don M, Luxford W, Shannon R, Sininger Y, Tonakawa L, Waring M
Department of Neurology, California College of Medicine, University of California, Irvine 92717.
Brain. 1991 Jun;114 ( Pt 3):1157-80. doi: 10.1093/brain/114.3.1157.
An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing.
一名11岁女孩对她能清晰听到的短声和短纯音刺激的听觉诱发电位（脑干、中潜伏期和长潜伏期）的感觉成分缺失。心理声学测试显示，那些依赖时间线索的听觉感知有明显损害，即双耳短声的侧向化、双耳掩蔽阈值随信号相位变化的改变、双耳节拍、成对单耳短声的检测、声音中无声间隙的单耳检测以及短持续时间纯音的单耳阈值升高。相比之下，反映强度或频率辨别（差别阈）的听觉功能仅受到轻微损害。纯音听力测试显示中度（50分贝）双侧听力损失，且言语清晰度严重不成比例地丧失。保留的那些听觉诱发电位包括：（1）反映毛细胞活动的耳蜗微音器电位；（2）反映缓慢变化信号处理的皮质持续电位；以及（3）反映内源性听觉认知过程的长潜伏期认知成分（P300、处理负波）。诱发电位和感知缺陷都归因于声信号时间编码的变化，这可能发生在毛细胞和第八神经树突之间的突触处。结合先前发表的听觉诱发电位缺失但听力保留的病例对该患者的结果进行了讨论。
