Investigation of pure-tone hearing levels at a single frequency in sudden deafness.

Hearing levels in patients with sudden deafness are commonly discussed in terms of average thresholds at 3 or 5 frequencies, but an investigation of hearing levels at a single frequency is also important. In this paper, pure tone thresholds at 500 Hz and 4,000 Hz were investigated in patients with sudden deafness who came to our clinic within 4 days of onset. Particular attention was paid to the relationship between audiometric types according to the contour of the initial loss and degree of hearing recovery at each frequency. In the group of patients whose initial hearing level at 500 Hz was between 55 and 70 dB, the hearing recovery at 500 Hz in the upward slope type was significantly greater than that in the downward slope type, but in other groups no significant differences in hearing recovery were observed among the different types of initial audiograms. We considered that the hearing recovery at a single frequency was not related to the audiometric type except in the patients with the upward slope type with moderate hearing loss.