[Prognosis of acute low-tone sensorineural hearing loss]

We studied 50 patients with acute low-tone sensorineural hearing loss (ALHL) who were examined at the Department of Otolaryngology, University of Tokyo, and followed up for 18 months or more. We investigated the prognosis of hearing loss within 3 months after onset, rate of recurrence during long-term follow-up, interval between the first and the second episodes of hearing loss or between onset and the time when the diagnosis of Meniere's disease was made, and factors affecting prognosis. The results were as follows. 1. Within the initial 3 months of follow-up, hearing loss continued to fluctuate in 5 patients. In the remaining 45, hearing returned to normal in 34, improved without returning to normal in 6, showed no marked change in 4, and became worse in one. 2. In long-term follow-up, the recurrence of hearing loss without vertigo occurred in 16 patients, and 5 others were eventually diagnosed as having Meniere's disease. The average interval between the first and second episodes of hearing loss was 9.2 months, and the diagnosis of Meniere's disease was made an average of 27 months after onset. 3. Recurrence was not significantly related to the initial prognosis of hearing loss. 4. Within the initial 3 months of follow-up, the prognosis of hearing loss was significantly better in patients whose hearing loss at 1 kHz was within 20 dB, and tended to be better in females and in patients attending within one week of onset. Long-term follow-up showed that the rate of recurrence was significantly lower in patients aged 40 years or more, and tended to be lower in patients who visited the hospital within one week of onset or whose hearing loss at 1 kHz was within 20 dB. 5. There were no significant differences between patients with single and recurrent attacks with respect to sex, subjective symptoms, and results of the glycerol test and electrocochleography. ALHL tends to recur without any relationship to the initial prognosis of hearing loss. Since it is still difficult to predict whether or not hearing loss will recur, long-term follow-up is necessary even in patients with good initial prognosis.