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Background and Aim: While most of the people with tinnitus have some degrees of hearing impairment, a small percent of patients admitted to ear, nose and throat clinics or hearing evaluation centers are those who complain of tinnitus despite having normal hearing thresholds. This study was performed to better understanding of the reasons of probable causes of tinnitus and to investigate possible changes in the auditory brainstem function in normal-hearing patients with chronic tinnitus.

Methods: In this comparative cross-sectional, descriptive and analytic study, 52 ears (26 with and 26 without tinnitus) were examined. Components of the auditory brainstem response (ABR) including wave latencies and wave amplitudes were determined in the two groups and analyzed using appropriate statistical methods.

Results: The mean differences between the absolute latencies of waves I, III and V was less than 0.1 ms between the two groups that was not statistically significant. Also, the interpeak latency values of waves I-III, III-V and I-V in both groups had no significant difference. Only, the V/I amplitude ratio in the tinnitus group was significantly higher (p=0.04).

Conclusion: The changes observed in amplitude of waves, especially in the latter ones, can be considered as an indication of plastic changes in neuronal activity and its possible role in generation of tinnitus in normal-hearing patients.

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Background and Aim: Speech-evoked auditory brainstem responses were used in the assessment of subcortical encoding of the speech stimuli in the English language. These processes are affected by language background and experiences. Considering the language specific acoustic differences, the aim of current study was establishing the response norms in adult Persian-speakers and comparing the encoding of the speech syllable /da/ between Persian and English languages.

Methods: Auditory brainstem responses to speech syllable /da/ in the right ear, gained from 48 normal adults (25 women and 23 men) with the mean age of 22.70 with SD 2.05 years were recorded. After characterizing the onset elements, transition from consonant to vowel, the periodic portion and offset of response, the Persian dataset were compared with 95% confidence interval norms in the age range of 18-28 years.

Results: The response to speech syllable /da/ was successfully recorded in all of the subjects and main features of response were highly overlapped with published English norms.

Conclusion: Normative values for speech-evoked auditory brainstem responses in adult Persian speakers are presented in the current survey. Our findings suggest that the recommended procedure and more importantly, the scoring method based on English norms can be used in Persian speakers without replacing the original synthetic vowel /da/.

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Background and Aim: CE-Chirp stimulus has been developed for stimulating more apical regions of the cochlea. Inadequacy of clinical information on the latency and amplitude characteristics of ABR evoked by CE-chirp at different levels in addition to discrepancy in identifying earlier ABR waveforms using CE-chirp stimulus are the reasons of this study.

Methods: This study was done by recoding ABR to click and broad-band CE-chirp stimuli in the right ear of 15 non-randomly selected normal-hearing individuals with age range of 20-30 years old. Frequency of recordable waves I and III, as well as threshold, amplitude, and latency of wave V were compared in response to click and CE-Chirp at 20-80 dB nHL.

Results: At 80 dB nHL, click stimulus evokes waves I and III more frequently than chirp stimulus (p=0.012 and p=0.016 respectively). At 20 and 40 dB nHL, wave V latency evoked by CE-Chirp is significantly longer than wave V latency evoked by click (p=0.012 and p=0.0001 respectively) however, at 80 dB nHL wave V latency evoked by CE-Chirp is shorter than click (p=0.0001). Wave V amplitude for CE-Chirp is significantly larger than for click at levels of 20, 40 and 60 dB nHL (p=0.0001, p=0.0001 and p=0.013 respectively). Wave V threshold is approximately 5 dB lower with CE-chirp compared to click (p=0.014).

Conclusion: Except at high levels, CE-Chirp evokes wave V with larger amplitude and lower threshold than click. Possibility of recording earlier ABR waves is reduced with CE-chirp stimulus.