Early diagnosis of endolymphatic hydrops with distortion. Product otoacoustic emissions

The present investigation was specifically designed to evaluate the ability of the glycerol test combined with pure-tone audiometry, distortion-product otoacoustic emissions (DPOAEs) to diagnose endolymphatic hydrops early and to identify patients who may evolve toward Meniere's disease. This investigation consisted of 43 consecutive patients with daily episodes of tinnitus with duration exceeding few hours or with continuous tinnitus who received no treatment. These were the unique symptoms reported by the patients. Each patient underwent glycerol testing measured with conventional pure tone audiometry and with distortion product otoacoustic emissions (DPOAEs). For the traditional pure-tone glycerol test a hearing improvement of at least 10 dB, at the lower two or three frequencies (125,250 and 500 Hz) was judged as positive result. For the DPOAEs glycerol testing, a smaller positive difference (5 dB) for at least three frequencies was interpreted as a significant fluctuation. Twenty four patients showed negative glycerol test both with pure tone audiometry and DPOAEs. In 7 cases the improvement was concurrently observed. In 9 patients post-glycerol changes appeared only in the DPOAEs outcomes. Finally the remaining three patients had two different patterns. Two had different ameliorations of the DPOAEs and pure-audiometry on the left and right sides respectively, and in the last one only post-glycerol, audiograms recovered. The present study re-confirms the potentiality of DPOAEs associated with glycerol test in diagnosing endolymphatic hydrops precociously. The possibility of these patients degenerating into Meniere's disease should not be underestimated.