Topodiagnostic assessment of occupational noise-induced hearing loss using distortion-product otoacoustic emissions compared to the short increment sensitivity index test.

Because the efforts needed to produce an "automatic audiogram" by means of distortion-product otoacoustic emissions (DPOAE) are still experimental, their capacity to produce objective topodiagnostic information must still be defined. In the present study results of the short increment sensitivity index testing (SISI) test in 97 patients with noise-induced hearing loss (NIHL) were compared with those of a DP-gram. Pure tone, speech and impedance audiometry, SISI tests and DPOAE measurements were performed on all patients. SISI was measured in both ears of 93 patients and unilaterally in 4 patients. SISI was also determined at two frequencies in 46 patients. Six measurements were rejected because of conductive hearing losses in adjacent frequencies. In all, 230 measurements could be compared. After classifying topodiagnostic results of the SISI test and DP-gram into cochlear, inconclusive and retrocochlear lesions, statistically significant correlations were found and differences were noted in only 18% of cases. Findings demonstrated the superiority of DPOAE to the SISI test in obtaining topodiagnostic information about inner ear disease.