Tehran University Medical Journal

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Background: Auditory brainstem response (A.B.R) is one of the most important electrophysiological tests in evaluating of auditory system, especially for diagnosing of auditory nerve and brainstem disorders. It is a non-invasive test and has reliability and validity characteristic. There is no contra-indication for this test. One of the most important of stimulation parameters of A.B.R is click polarity (rarefaction, condensation and alternative). Some of the investigators believed that different polarities have no effects on A.B.R are affected by different polarities.

Materials and Methods: In this study, the results of ABR of 148 patients (296 ears) were compared with three different polarities of rarefaction, condensation and alternative half click stimuli. The cases were categorized in three groups of normal (60 cases), cochlear (62 cases) and retro-cochlear (17 cases). This classification were done according to the hearing level in pure tone audiometry results in three frequencies of 1000, 2000, 4000 Hz and to the site of the their disorders. The mean absolute latencies of waves I, III and V were obtained for each polarity. Inter-peak latency (I.P.L) of wave also measured in three groups (normal, cochlear and retro-cochlear).

Results: The results were showed a significant difference between absolute latency of wave I among different polarities on three above mentioned groups (P<0.05). There were no significant discrepancy for other waves of III and V and Inter-peak latency (I.P.L) of wave I to (P>0.05).

Conclusion: It was concluded that rarefaction polarity has better and more stable results of ABR tests.

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Background: Respiratory distress syndrome is developmental immaturity of lungs, that is caused by lack of surfactant. Lack of surfactant lead to wide atelectasis and arterial hypoxemia which is a life-threatening lung disorder. The aim of this study was to compare the function of cochlear in infant who suffer respiratory distress syndrome with normal infants by transient evoked otoacoustic emission (TEOAE) test. Methods: This descriptive- analytic cross sectional study was carried out on 21 respiratory distress syndrome (RDS) infants (42 ear) that consists of 11 male and 10 female, 21 normal infants (42 ear) that consists of 10 male and 11 female in Mirza Koochakkhan Hospital, Tehran University of Medical Sciences, Tehran, Iran, which all of them were 3 to 6 month year old, to collect informations about the health of infants we used the files in hospital and to assess the cochlear function we used computerized recording by TEOAE instrument. Statistical analysis carried out by SPSS software version 17 and Chi-square test. Results: The results of TEOAE test demonstrated that in normal group there is no statistical differences between ears and gender, also there was no statistical differences between ears in respiratory distress syndrome group but there was statistical differences between gender in this group. The frequency of pass result (show normal function of outer hair cell in cochlea) was greater in male than female in male the frequency of pass result was 17 ear (77.3%) but in female was 8 ear (40%). In TEOAE test results there was statistical differences between two groups of study. The frequency of pass result in normal group was 34 ear (81%) and in respiratory distress syndrome group was 25 ear (59%) which was significantly more in normal group than in respiratory distress syndrome infants (P= 0.032). Conclusion: According to results, it seems that the respiratory distress syndrome could affects the cochlear and the function of outer hair cell in it so in infants who suffer respiratory distress syndrome we should use the test battery of hearing.