Tehran University Medical Journal

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.

Background: Cerebrovasular diseases (CVD) are one of the most common anomalies which may affect on auditory cortex. In this research we have tried to evaluate the function of CANS in a group of 50-70 years old cerebrovascular accident (CVA) patients without hearing problem by using Persian version of C.S.T.

Materials and Methods: This cross-sectional analytic study was established at Loghman-e-Hakim Hospital on a group of 30 normal subject (15 male, 14 female) and a group of 40 patients with CVA including 30 patients (16 male, 14 female) with abnormal CT scan and 10 patients with normal CT scan.

Results: Routine audiologic test including: Pure tone audiometry, Immitance audiometry and speech audiometry were nearly normal in all cases. There were significant differences between mean scores of CST in the patients with CVA and control group (P< 0.05). There were no significant differences between mean scores of CST in male and females (P> 0.05). In spite of nearly normal hearing and high scores in the simple speech tests such as SDS, there were significant differences in mean scores of CST in both ears of CVA patients (P< 0.05). Another important point is that in some of patients with CVA.

Conclusion: Although common radiologic evaluations such as CT scan showed no anatomic or structural anomaly but central auditory assessments such as CST can show dysfunctions of CANS. Therefore, CST might be a valuable test in CANS batteries for the cerebrovascular diseases.