か電図所見と聴力の関係

Abstract

Transtympanic electrocochleography (ECoG) with clicks and tone-bursts at a frequency of 1000 Hz was performed in 155 patients (160 ears) who visited JA Yamaguchi Shuto General Hospital. Action potentials (AP), negative summating potentials (—SP) and cochlear microphonics (CM) were examined.1) Click-evoked AP detection thresholds and tone-burst-evoked CM detection thresholds were cor-related with pure tone thresholds at frequencies of 1000 Hz and 4000 Hz, and with average pure tone hearing levels in the frequency range of 500-4000 Hz. Click-evoked AP detection thresholds correlated well with pure tone thresholds at a frequency of 4000 Hz (correlation coefficient: 0.800).2) Click-evoked AP detection thresholds in patients with high-frequency hearing loss were higher than those in patients with low-frequency hearing loss.Click-evoked AP amplitudes in patients with high-frequency hearing loss were lower than those in patients with low-freuency hearing loss. There were significant differences in click-evoked AP thresholds and AP amplitudes between patients with high-frequency and low-frequency hearing loss. Click-evoked AP thus appeared to be related to high-frequency hearing loss.3) There were significant differences in average pure tone hearing levels in the frequency range of 500-4000 Hz, pure tone thresholds at frequencies of 1000 and 4000 Hz, click-evoked AP detection thresholds and amplitudes, and tone-burst-evoked CM detection thresholds between patients with and without a delayed response following CM.Patients with a delayed response following CM thus appeared to have better hearing levels and better ECoG waveform responses than did those without a delayed response following CM.