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Background and Aim: Auditory neuropathy (AN) can be diagnosed by abnormal auditory brainstem response (ABR), in the presence of normal cochlear  microphonic (CM) and otoacoustic emissions (OAEs).The aim of this study was to investigate the ABR and other electrodiagnostic test results of six patients suspicious to AN with problems in speech recognition.
Materials and Methods: this cross sectional study was conducted on 6 AN patients with different ages evaluated by pure tone audiometry, speech discrimition score (SDS) , immittance audiometry , electrocochleography , ABR, middle latancy response (MLR), late latency response (LLR), and OAEs.
Results: Behavioral pure tone audiometric tests showed moderate to profouned hearing loss. SDS was so poor which is not in accordance with pure tone thresholds. All patients had normal tympanogram but absent acoustic reflexes. CMs and OAEs were within normal limits. There was no contralateral suppression of OAEs. None of cases had normal ABR or MLR although LLR was recorded in 4.
Conclusion: All patients in this study are typical cases of auditory neuropathy. Despite having abnormal input, LLR remains normal that indicates differences in auditory evoked potentials related to required neural synchrony. These findings shows that auditory cortex may play a role in regulating presentation of deficient signals along auditory pathways in primary steps.

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Background and Aim:  Among all auditory assessment tools, auditory steady state response (ASSR) is a modern test. Modulation frequency for this test is usually 80 Hz. The purpose of this study, was to examined adult subjects with 40 Hz and 80 Hz ASSR and compare the results.
Materials and Methods: Thirty adult (60 ears) were evaluated by ASSR and PTA test, Results were divided into three groups: normal hearing, mild and moderate sensorineural hearing loss.
Results: In all groups, forty hertz ASSR thresholds were relatively closer to behavioral threshold than those of 80 Hz ASSR(p<0.05). Besides, the more severe hearing loss, the lower the difference between those two thresholds. Correlation coefficients were also higher in 40 Hz ASSR(p<0.05).
Conclusion: Frequency modulation thresholds with 40 Hz are more likely to be closer to the behavioral thresholds. Moreover, it has better results than the thresholds with 80 Hz.

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Background and Aim: As clinical audiometry assessment of each ear needs to know interaural attenuation (IA), the aim of this study was to investigate Persian speech IA in adults.

Methods: This cross-sectional, analytic study was performed on 50 normal hearing students (25 males, 25 females), aged 18-25 years old in Faculty of Rehabilitation, Tehran University of Medical Sciences. Speech reception threshold (SRT) was determined with descending method with and without noise. Then speech IA for Persian spondaic words was caculated with TDH-39 earphones.

Results: Mean speech IA was 53.06±3.25 dB. There was no significant difference between mean IA in males (53.88±2.93 dB) and females (52.24±3.40 dB)(p>0.05). The lowest IA was in females (45 dB) and the highest IA was in males (60 dB). Mother's language has no significant effect on speech IA.

Conclusion: We may consider 45 dB as the lowest IA for Persian speech assessment, however generalization needs more study on a larger sample.

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Background and Aim: Diabetes mellitus is a progressive metabolic disease. Studies about the relationship between diabetes mellitus and auditory impairment have shown variable results in supporting the fact that diabetes may have a complex repercussion on the auditory pathways. We aimed to evaluate hearing in patients with type II diabetes mellitus with behavioral and electrophysiological auditory tests.

Methods: In a cross-sectional study, we assessed 30 patients with type II diabetes mellitus with the mean age of 43.7 (SD: 1.3) years, ranging 40-45 years, and 30 matched healthy subjects with the mean age of 41.5 (SD: 1.5) years. Subjects were evaluated using auditory brainstem response (ABR) and pure tone audiometry. The results were compared between two groups.

Results: Pure tone audiometry was normal. There was a significant increased latency for waves I, III, and V, and also, interpeak latencies of I-III, III-V, and I-V waves (p<0.05).

Conclusion: ABR latency prolongation indicates abnormal nerve conduction velocity in patients with type II diabetes mellitus. ABR can be an important clinical tool for evaluating diabetes influence on cochlear nerve conduction velocity before hearing loss occurs in these patients.

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Background and Aim: The auditory steady state response is a modern test for estimating hearing thresholds, especially in difficult to test individuals . However, there are few bone conduction auditory steady state response data, particularly for individuals with hearing loss. The objective of this study was to investigate bone conduction auditory steady state response thresholds in individuals with sensorineural hearing loss and normal hearing.

Methods: In a cross-sectional study, 10 individuals with normal hearing and 10 with sensorineural hearing loss at the age of 15-30 years were selected by non-probability sampling. Auditory steady state response and pure tone audiometry to bone conduction stimuli in 500 and 2000 Hz were recorded in two groups. Paired and independent t-test were used to compare data between the groups.

Results: There was low correlation between bone conduction auditory steady state response and pure tone audiometry in both groups (p>0.05 for both). The difference of behavioral thresholds and auditory steady state response in 500 Hz was higher than 2000 Hz in both groups (p=0.033 for normal hearing and p=0.017 for sensorineural hearing loss groups). Comparison of these results showed significant differences between the two groups (p<0.001).

Conclusion: In both groups, there was low correlation between bone conduction auditory steady state response and pure tone audiometry thresholds. In individuals with sensorineural hearing loss and in higher frequencies , bone conduction auditory steady state response thresholds was closer to pure tone audiometery thresholds.

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Background and Aim: Diabetes mellitus is a metabolic disorder that affects multiple systems including the auditory and vestibular systems. Patients with diabetes mellitus complain of tinnitus and dizziness. The objective of this study is to assess the effects of diabetes mellitus types I and II on auditory and vestibular systems.

Methods: We compared pure-tone audiometric results and cervical vestibular evoked myogenic potentials ( cVEMPs) between 15 patients with diabetes mellitus type I (43.80 with SD 4.246), 15 patients with diabetes mellitus type II (48.13 with SD 2.973), and 10 normal volunteers (45.30 with SD 4.448). Age range of the participants was 40-50 years old.

Results: Audiometric results showed normal hearing in both types of diabetes mellitus. In contrast, comparing amplitude of cVEMPs between diabetes mellitus and control groups showed statistically significant differences (p<0.05).

Conclusion: In spite of normal audiometric results in patients with diabetes mellitus types I and II, there was abnormal vestibular responses involving vestibular end-organ and related central pathway.