The prognostic value of the otoacoustic emission test in low frequency sudden hearing loss

Low frequency sudden hearing loss (LFSHL) is a frequent finding in the otological practice. Several prognostic indicators have been suggested concerning the prediction of the outcome of sudden hearing loss, but so far there are no proven factors to establish the prognosis. The aim of this study was to assess whether OAEs could be considered as a reliable prognostic test in LFSHL. The study group consisted of 20 patients presenting with a unilateral LFSHL. Each patient was submitted to spontaneous otoacoustic emissions (SOAEs), transient otoacoustic emissions (TEOAEs) and distortion products (DPOAEs) recording and then treated with glycerol administrated intravenously in 3-h intervals for 4 days. Pure tone audiometry (PTA) threshold was evaluated again 1 h after the last administration of glycerol. After osmotic therapy 12 patients (60%) showed a significant PTA improvement with a mean improvement of 11 dB; modifications were significant at the Student's t test for paired data (P<0.0001). The relationship between the pretherapy presence or absence of SOAEs, TEOAEs and DPOAEs and PTA modification was not significant at the exact Fisher's test. In conclusion, even if our study supports that OAEs could be an indicator of the inner ear functional state, they cannot be utilized as a prognostic test in LFSHL in relation to the efficacy of osmotic therapy. Among the other parameters evaluated, only the precocity of therapy seems to be related to prognosis in LFSHL.