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Assessment of Latency and Amplitude Based on Polarity Change in Auditory-Evoked Brainstem Responses of Normal Hearing Individuals

Deniz Uğur Cengiz, Selim Ünsal and Mehmet Gündüz

Auditory brainstem response (ABR) evaluations yield different results depending on the polarity. Which polarity should I prefer in ABR evaluations? In individuals with normal hearing, we are trying to find a solution to the problem by assessing wave latencies, interwave latency values, amplitudes and morphology obtained through changes in intensity and polarity. A total of 39 people (20 males, 19 females) aged 18–45 (with a mean of 29.06 ± 9.56) with normal hearing participated in this study. Pure-tone audiometry, immitansmetric measurements, Otoacoustic emission (OAE) and ABR tests were administered to all participants after an ear-nose-throat examination. In the ABR test, the latencies of waves I, III, and V, the interwave latency values of I–III, III–V, and I–V, and amplitude values of wave V were evaluated at 70 dBnHL intensity level through the alternate, rarefaction and condensation polarities. The wave latencies, interwave latencies and amplitude values obtained through the alternate, rarefaction and condensation polarities were compared. Repeated measures Analysis of variance (ANOVA) was used for differences between groups. At 70 dBnHL intensity, the latencies of waves I and III were obtained the earliest through the rarefaction polarity, while the latency of wave V was obtained in the shortest amount of time through the alternate polarity (p<0.05). At 20 and 50 dBnHL intensity levels, the latencies of wave V were obtained the earliest through the alternate polarity method, although there was statistically significant 50 dBnHL intensity (p<0.05), there was not statistically significant 20 dBnHL intensity (p>0.05). There was no statistically significant difference in the interwave latency values regarding the polarities (p>0.05). At 20 and 50 dBnHL intensity levels, the highest amplitude values of wave V were obtained through the rarefaction polarity (p<0.05). At 70 dBnHL intensity, the highest amplitude values of wave V were obtained through the alternate and condensation polarities, although these were not statistically significant (p>0.05). There was no statistically significant difference between the demographic characteristics of individuals and the polarities. Based on the findings, different latency and amplitude values are observed between polarities. When creating normal values in clinics or using the present normative data, the preferred polarities should be taken into account. Variables depending on polarities are of great importance in terms of diagnosis in ABR evaluations.