[Analysis of otoacoustic distortion products in a group of otosclerotic patients].

There is indication that middle ear pathologies can affect otoacoustic emissions (OAE) to varying degrees. In fact, since acoustic emissions are recorded in the outer ear duct, the energy transfer mechanisms both up and downstream of the middle ear must be intact. OAE distortion products (DP) enable one to analyze cochlear response by frequency and to verify the retrograde response as a function of frequency. In the present work this method was used to test otosclerosis patients. A group of 45 patients with otosclerosis was tested to determine whether the OAE-DP could be identified and measured. Subsequently the characteristics of these DPs were analyzed in a group of 18 subjects who had previously undergone stapedectomy. All the results obtained were compared with those from a control group of normal hearing subjects with normal emissions and free of any E.N.T. pathology. In approximately half of the cases (53%) in the otosclerosis patient group it was possible to detect clearly evident DPs. Obviously, the DP-Gram differed greatly and average amplitude was lower than those found in normal subjects. Indeed, there was no signal at all at the lower and middle frequencies reflecting a hearing loss typical of cases of otosclerosis. Most (58%) of the otosclerosis patients who had successfully undergone stapedectomy recorded valid DPs. The DP-Gram frequency range was much broader (750-4000 Hz) than in those who had not undergone surgery. Moreover the lower and mid frequency amplitudes were significantly better. The data obtained are quite encouraging and suggest that DP should be studied in depth in patients with otosclerosis.