内耳性難聴を伴った機能性難聴の２例―耳音響放射検査の診断的有用性―

Abstract

We report two cases of pseudohypacusis with organic hearing loss in which useful diagnostic information could be obtained from otoacoustic emission (OAE) testing.Case 1 was a 12-year-old female who had complained of fluctuating hearing loss for a few years. Although her initial pure-tone audiogram indicated moderate hearing loss in both ears, speech audiometry strongly suggested that the hearing of her left ear was considerably better than anticipated based on the pure-tone testing. Since the wave V thresholds of auditory brainstem response (ABR) were 70 and 20dBnHL in the right and left ear, respectively, it was suspected that she had moderate hearing loss in the right ear and normal hearing sensitivity in the left ear. However, OAE testing subsequently performed revealed moderate to severe hearing loss in all frequency regions except between 1.5 and 5kHz in her left ear, and this finding was also confirmed by follow-up pure-tone audiometry.Case 2 was a 54-year-old male whose complaints were left-sided hearing loss and tinnitus developing after a traffic accident. His initial pure-tone audiogram showed moderate to severe hearing loss in the left ear. However, his speech discrimination score for the left ear suggested much better hearing than expected from the pure-tone testing results, and mild hearing loss in the left ear was suspected based on ABR examined later. OAE testing was subsequently performed and revealed moderate to severe hearing loss in the frequency region above 3kHz in the left ear, a finding subsequently confirmed by pure-tone audiometry.The diagnosis of pseudohypacusis is sometimes difficult in patients with organic hearing loss, as in the two cases presented here. In such cases, frequency-specific information about cochlear function provided by OAE might be helpful for assessment of true hearing loss. From this perspective, OAE testing is considered useful as a diagnostic tool for pseudohypacusis.