耳鼻咽喉科臨床

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The purpose of this study was to elucidate the electrophysiological characteristics of summating potential, which we call here Pr. SP, and the pathophysiological significance of Pr. SP in the electrocochleogram in man. The electrocochleogram was recorded to tone burst stimuli using a transtympanic (promontory) technique in 22 adults with normal hearing, 19 patients with Meniere's disease and 23 patients with sensorineural hearing loss.
Measurements of Pr. SP were conducted mainly on the input-output relation, the amplitude and polarity versus the frequency relation and the correlation between the Pr. SP amplitude (μV) and the hearing level (dB HL) and the correlation between the Pr. SP threshold (visual detection level: dB SPL) and the hearing level.
The results and the conclusions were as follows:
Three methods were successfully devised to isolate a pure Pr. SP from the mixed pattern of responses composed of both Pr. SP and AP.
Our experiments made clear the fact that the electrophysiological characteristics of Pr. SP in man had the composite features of both components of AVE. SP and DIF. SP recorded from the basal turn of the guinea pig cochlea.
It was inferred from our electrophysiological analysis of Pr. SP that the main component of Pr. SP was a receptor potential generated from cochlear hair cells.
The dominantly negative Pr. SP was recorded from 63% of the patients with Meniere's disease. In this group, we found no correlation between the Pr. SP amplitude and the hearing level, and between the Pr. SP threshold and the hearing level.
Most cases of sensorineural hearing loss were characterized by a decrease or disappearance in the Pr. SP amplitude. In this group, we found a significant correlation between the Pr. SP amplitude and the hearing level, and between the Pr. SP threshold and the hearing level.
It was concluded from our results that the diagnostic significance of Pr. SP in inner ear disease will be to detect abnormal function of the receptor organ at the presynaptic level of the cochlea.

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