Evoked Otoacoustic Emissions in Ears with Sudden Deafness and with Low Tone Sensorineural Hearing Impairment

In order to elucidate pathosis of acute sensorineural deafness and low tone hearing loss, so-called low tone sudden deafness, evoked otoacoustic emissions (EOAEs) were examined. There was a significant correlation between mean pure tone audiometric thresholds and EOAE detection thresholds in 46 ears of sudden deafness in which 1kHz hearing thresholds were lower than 55dB. Scatter-plot of 24 ears with low tone hearing loss distributed roughly along the regression line obtained from the plot of sudden deafness. Mean detection threshold of EOAEs in ears with low tone hearing loss was 12dB lower than that in sudden deafness, in comparison with those ears with hearing threshold below 30dB at 1kHz. In addition to our previous findings of low and high tone hearing loss ears, the difference was understood by the traveling wave theory of the basilar membrane vibration. The pathosis of low tone sudden deafness is similar to that of moderate or middle grade sudden deafness, in respect to a disorder of the intracochlear micromechanics.