Differences between Click and Toneburst as a Sound Stimulus in Clinical Electrocochleography

Abstract

Electrocochleography (ECochG) was used to test 137 ears of patients with definite Meniere's disease, 29 normal ears and 383 ears with other types of sensorineural hearing loss. One of the questions raised in clinical ECochG is whether to use a clik or a toneburst to diagnose endolymphatic hydrops using SP/ AP. First, it was shown that SP/AP was much more useful than SP amplitude in the diagnosis of Meniere's disease. All investigators employing both the extra-and transtympanic approaches, except two study groups, used a click for detecting endolymphatic hydrops. There was no significant difference in SP/AP between click and tone-burst use in any disease in our clinic.Many investigators have proposed a normal upper limit of SP/AP with a mean+2 SD, a 99 % confidence limit or a mean+3 SD, and have used those limits to diagnose endolymphatic hydrops. Those limits vary from 0.30 to 0.51. The mean values proposed by all study groups show little difference, being close to 0.25, in spite of differences in intensities and intervals of stimulus and high cut and low cut filters in the preamplifier. Any differences depend on the statistical decision of the limit and the size of standard deviation.It was concluded that both stimuli could be used in clinical ECochG and 0.30 to 0.40 of SP/AP would be adequate as the normal upper limit. The statistical normal range was determined at a mean+2 SD or 99% confidence limit.