To clarify the pathogenesis of acute low-tone sensorineural hearing loss (ALHL), we retrospectively compared the electrocochleographic findings from 20 patients with ALHL with those from 58 patients with Meniere's disease (MD) classified into 4 groups (MD1 through MD4) according to their pure tone average. The mean summating potential-action potential ratio in the ALHL group was 0.35 +/- 0.13, which was significantly higher than the control ratio but similar to the ratio seen in the MD1 group (pure tone average < 25 dB hearing level). The mean detection threshold of the cochlear microphonics in the ALHL group was 32.0 +/- 9.4 dB normal hearing level, which was again similar to that seen in the MDI group. Moreover, more than 50% of patients with ALHL had normal cochlear microphonics input-output curves. We therefore conclude that the pathogenesis of ALHL arises from an endolymphatic hydrops with little or no impairment of hair cells that resembles early-stage MD.
We developed a system with a simple structure for sensing movement during swallowing through simple operations using piezoelectric poly(l-lactic acid) (PLLA) braided cords as a motion sensor. In the system, the analog-signal-processing part of the PLLA braided cord sensor is composed of analog-signal-adjusting parts, a multiplexer, an analog-to-digital (A/D) converter, and so forth, the data is processed on a personal computer, and finally the dependence of the signal intensity on the position and time of the motion during swallowing is plotted as a three-dimensional plot. The results of a swallowing function test using our developed system appeared to coincide with that of a diagnostic test described in a medical textbook. In addition, the subject experienced little restriction of the motion during the measurement using our system. The experimental results suggest that our system has potential use as a wearable device as a useful and portable tool for healthcare.
The changes of the action potential (AP), the summating potential (SP) and cochlear microphonics (CM) were investigated in reference to the grade of endolymphatic hydrops produced by endolymphatic sac obliteration in guinea pigs. In a few cases with minimum endolymphatic hydrops, super-normal AP was obtained. With an increase of endolymphatic hydrops, CM responses were reduced although AP responses at intensive stimulation were maintained relatively well. It is thought that the polarity of positive SP, as observed in control, was influenced to deflect towards negative SP by an interaction between the increased degree of endolymphatic hydrops and the changes of the biochemical components of the inner ear fluids.
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