Arakawa K
Department of Otorhinolaryngology, Dokkyo University School of Medicine, Tochigi.
Nihon Jibiinkoka Gakkai Kaiho. 1998 Jan;101(1):53-62. doi: 10.3950/jibiinkoka.101.53.
It is now well documented that in cases of Menière's disease/endolymphatic hydrops, the electrocochleography (ECochG) evoked by a broad-band click is often characterized by an enlarged summating potential (enlarged-SP) and a large negative summating potential to action potential ratio (large -SP/AP) but these mechanism have not been clarified. The aim of this study was to find clues to the mechanism of enhanced -SP and large -SP/AP in Menière's disease, by using long-tone burst stimuli. We also sought to determine the significance of SP measurement for evaluating the cochlear function in Menière's disease/endolymphatic hydrops. ECochG was performed on 29 ears of patients with Menière's disease and 12 ears of adults with normal hearing as a control group. Extratympanic ECochG was carried out using an HN-7 electrode. The sound intensity used for measuring the SP and SP/AP was 90dBnHL. Both SP and AP were elicited by clicks and long-tone bursts of 50 ms duration with a 1-ms rise-fall time. The clicks and long-tone bursts with frequencies of 0.5, 1, 2, and 4 kHz were delivered by the tubal transducer (NC-3). In most of the patients with Menière's disease, SP evoked by the long tone burst stimuli showed negative polarity (-SP) at each frequency. Analysis of variance (X2test) indicated a significant difference in -SP at 0.5 and 1 kHz between Menière's disease and the control group (0.5 kHz: p < 0.001, 1 kHz: p < 0.02). When setting the normal upper limit of the -SP/AP to 0.4, we found that the number of cases over 0.4 which showed -SP at 0.5 and 1 kHz was much larger than those below 0.4 in the 29 ears of patients with Menière's disease. There was no difference between the types of Menière's disease or glycerol test and SP polarity elicited by long-tone burst stimuli. The enhanced -SP and large -SP/AP obtained by the broad band clicks seem to reflect a component of negative SP polarity in the low and middle frequency ranges. It was assumed that the reverse phenomena of SP polarity in the low and middle frequency ranges were related to changes in hydrodynamic characteristics in the upper cochlear turns due to abnormal endolymphatic pressure. Our findings suggest that SP recording by long-tone burst stimuli is useful in detecting changes in cochlear partition due to abnormal intracochlear pressure, most likely in the early phase of Menière's disease based on the wide frequency information of SP.
现已充分证明，在梅尼埃病/内淋巴积水病例中，宽带短声诱发的耳蜗电图（ECochG）通常表现为总和电位增大（增大-SP）以及总和电位与动作电位的比率增大（大-SP/AP），但这些机制尚未阐明。本研究的目的是通过使用长纯音刺激来寻找梅尼埃病中-SP增强和大-SP/AP的机制线索。我们还试图确定测量SP对评估梅尼埃病/内淋巴积水患者耳蜗功能的意义。对29例梅尼埃病患者的耳朵和12例听力正常的成年人耳朵进行了ECochG检查作为对照组。使用HN-7电极进行鼓室外ECochG检查。测量SP和SP/AP时使用的声强为90dBnHL。SP和AP均由短声以及持续时间为50ms、上升-下降时间为1ms的长纯音诱发。频率为0.5、1、2和4kHz的短声和长纯音由咽鼓管换能器（NC-3）发出。在大多数梅尼埃病患者中，长纯音刺激诱发的SP在每个频率均表现为负极性（-SP）。方差分析（X2检验）表明，梅尼埃病组与对照组在0.5kHz和1kHz频率下的-SP存在显著差异（0.5kHz：p<0.001，1kHz：p<0.02）。当将-SP/AP的正常上限设定为0.4时，我们发现，在29例梅尼埃病患者的耳朵中，0.5kHz和1kHz频率下-SP大于0.4的病例数远多于小于0.4的病例数。梅尼埃病的类型或甘油试验与长纯音刺激诱发的SP极性之间没有差异。宽带短声获得的-SP增强和大-SP/AP似乎反映了低频和中频范围内负极性SP成分。据推测，低频和中频范围内SP极性的反转现象与内淋巴压力异常导致的蜗顶流体动力学特性变化有关。我们的研究结果表明，基于SP的宽频率信息，长纯音刺激记录SP有助于检测耳蜗内压力异常引起的耳蜗分隔变化，很可能在梅尼埃病的早期阶段。
