[Effect of sound conditioning on click auditory brainstem response threshold shifts in guinea pigs]

Sound conditioning is exposure to a non-traumatic, moderate level of sound which increases inner ear resistance against further severe noise. In this study, we aimed to survey the effect of sound conditioning on auditory brainstem response [ABR] threshold shifts using click stimulus, and the effect of the frequency of conditioning on hearing protection. Fifteen guinea pigs were randomly divided into 3 groups. Two conditioned groups were exposed to 1 kHz, and 4 kHz octave band noise at 85 dB SPL, 6 hours per day for 5 days, respectively. On the sixth day, the animals were exposed to 4 kHz octave band noise at 105 dB SPL, for 4 hours. The control group was exposed to intense noise, 4 kHz at 105 Db SPL for 4 hours [without conditioning]. After exposure, ABR thresholds using click were recorded an hour, and 7 days after noise exposure. The results of the ABR with click stimulus showed less thresold shifts in conditioned groups than control [p 0.05]. Electrophysiological data of our study showed that sound conditioning has a protective effect against subsequent intensive noise exposure, and the frequency of conditioning does not have significant effect on ABR threshold shifts when using click stimulus

[Electrophysiologic and behavioral assessment of hearing status in children with spastic diplegia]

High incidence of speech disorders in children with cerebral palsy could be related to a deficiency in processing of auditory stimuli. So it is vital to check out any peripheral or central disorders in auditory system using behvavioral and electrophysiological auditory tests. In a cross-sectional study, 15 children with spastic diplegia, mean age 5.77, SD 2.26 years, and 15 normal children, mean age 5.33, SD 1.80 years, were tested using pure tone audiometry, imittance and auditory brainstem responses. The results were compared between the two groups. Hearing thresholds and middle ear status were in normal range in all participants; however, contralateral acoustic reflex thresholds were mostly elevated. Comparing absolute latency and interpeak latency intervals of auditory brainstem responses between the two groups, absolute latency interval of later waves, and in specific the V wave, was significantly longer in diplegic children [p=0.04] resulting in a longer III-V interpeak latency intervals [p=0.02]. Neurological disorders in pont-o-reticulo-spinal pathway, pontine reticular nuclei and upper pons which are adjacent to adutory nuclei of lateral leminiscus and inferior colliculus result in auditory dys-synchrony and increased latency intervals in latter waves of auditory brainstem responses. This could also attributed to functional disorders in wave-generating sites in these patients

[Protective effect of n-acetylcysteine on the hearing of rabbits exposed to noise and carbon monoxide]

One of the chemical pollutions which is frequently common in industry-other than noise is carbon monoxide. The present study aimed to assess the putative protective effect of N-acetylcysteine on the function of outer hair cells of rabbits exposed simultaneously to noise and carbon monoxide. 24 male rabbits are entered in this interventional study. After obtaining baseline distortion product otoacoustic emissions, rabbits were randomly devided into four groups. The groups included: exposed with noise and received saline, exposed with noise and carbon monoxide and received saline, exposed with noise and received N-acetylcysteine, and exposed with noise and carbon monoxide and received N-acetylcysteine. Subsequently, they were evaluated again with distortion product otoacoustic emissions in two stages [two hours and one week after the exposure]. Data were recorded and analyzed using paired and independent sample t-tests. Exposure to noise, and also simultaneous exposure to noise and carbon monoxide, and moreover using N-acetylcysteine in both groups, produced significant changes in distortion product otoacoustic emissions amplitudes [p<0.005]. The findings of the present research reveal that simultaneous exposure to noise and carbon monoxide may potentiate noise induced hearing loss. In addition, utilizing N-acetylcysteine can be used as a preventive agent for noise induced hearing loss and to avoid its potentiation with carbon monoxide

[Study of noise effects on rabbit's hearing status using distortion product otoacoustic emissions]

Noise-induced hearing loss is the most common problem in industrial areas. This study aimed to determine effects of excessive noise exposure on measurable characteristics of distortion product otoacoustic emissions [DPOAEs] in rabbits. The study was carried out on 12 adult male New Zealand White rabbits including case group - exposed to 500-8000 Hz broadband white noise with 100 dBA SPL for 8 hours per day in 5 consecutive days - and control group. After three days period of acclimatization to the experimental condition, rabbits' hearing status in each group were measured by distortion product otoacoustic emissions on days zero means before the study was initiated as a baseline, eight, one hour after the latest exposure to noise, and ten. The recorded results were analyzed using SPSS software. Highest mean distortion product otoacoustic emissions amplitudes in case group were allocated to frequencies of 5888.50 Hz, 8166.50 Hz, 9855.00 Hz, 3956.00 Hz, and 3098.50 Hz, respectively. However, the lowest mean distortion product otoacoustic emissions amplitude was related to frequency of 588.00 Hz [p=0.001]. This study revealed that distortion product otoacoustic emissions amplitude shifts due to noise occur first in high and then in middle frequencies. Additionally, exposure to noise can decrease distortion product otoacoustic emissions amplitudes. We conclude that distortion product otoacoustic emissions can be a reliable test for estimating personal susceptibility to noise-induced hearing loss

Reliability and validity of the bipolar depression rating scale on an Iranian sample

The Bipolar Depression Rating Scale is an instrument to measure depression severity in patients diagnosed with bipolar disorder. This study has reevaluated the psychometric values of the Bipolar Depression Rating Scale through assessing an Iranian sample of patients with bipolar depression. A total of 60 patients [36 males and 24 females] with bipolar depression referred to four medical centers in Tehran, Iran were interviewed with the Structured Clinical Interview for DSM-IV axis I Disorders, Young Mania Rating Scale, center for Epidemiological Studies Depression Scale, and the Bipolar Depression Rating Scale. Internal consistency and inter-rater reliability of the Bipolar Depression Rating Scale, and Pearson's correlation coefficient between the Bipolar Depression Rating Scale and Young Mania Rating Scale/Center for Epidemiological Studies Depression Scale were calculated. The Cronbach's alpha coefficient was 0.81. The Pearson's correlation coefficients of the Bipolar Depression Rating Scale with the Center for Epidemiological Studies Depression Scale and Young Mania Rating Scale were 0.73 and-0.82, respectively. The correlation coefficients between the two raters for the total score of the Bipolar Depression Rating Scale according to the Pearson's correlation and intraclass correlation tests were 0.83 and 0.89, respectively. The Bipolar Depression Rating Scale is a reliable and valid instrument to use in studies on Iranian clinical patients with bipolar depression

[Comparison of the prevalence and latency of vestibular evoked myogenic potentials in normal participants and symptomatic and asymptomatic Meniere's disease patients]

Vestibular evoked myogenic potentials [VEMP] originate from the saccule and the inferior vestibular nerve. In this study, the prevalence of VEMP and latency of the p13 and n 23 were compared between three groups of individuals, including symptomatic and asymptomatic Meniere's disease cases and normal participants. This study was conducted on 42 cases with the mean age of 40.48 years; thirty were Meniere's disease patients, of which 19 were symptomatic and 11 were asymptomatic; twelve were normal participants. The VEMP were recorded with 500 Hz tone bursts at 120 dBpeSPL. Then the prevalence and latency of the waves were analyzed and compared in the three above mentioned groups. The prevalence of VEMP in symptomatic Meniere's disease patients [52.6%] was significantly less than asymptomatic individuals [90.9%] and also normal subjects [100%] [p<0.05]. There was no significant difference between latencies of the waves in these three groups [p>0.05]. The latency of p13 for symptomatic, asymptomatic and normal participants was 16.41, 15.20 and 14.14 ms, respectively and the latency of n23 for these groups was 20.25, 18.77 and 18.50 ms, respectively. In Meniere's disease, after medical management, the succule probably regains normal function resulting in re-existence of VEMP. It seems that there is no change in the latency of the waves, most likely in re-existence of VEMP. It seems that there is no change in the latency of the waves, most likely due to involvement of the inner ear and intactness of the nerve. VEMP may be a useful test for diagnosis of Meniere's disease and additionally for monitoring the trend of medical management

Comparison of short tone burst-evoked and click-evoked vestibular myogenic potentials in healthy adults

Vestibular evoked myogenic potential [VEMPs] is one of the clinical tools to evaluate vestibular function. The VEMPs can be recorded from sternocleidomastoid muscle by auditory stimulation with various sound stimuli and are thought to have saccular origin. The aim of this study was to compare the VEMP responses evoked by short [500 Hz] tone burst [STB] with those evoked by click stimuli in healthy young individuals. Thirty healthy volunteers [15 males, 15 females] with ages of 18 to 30 years were enrolled in this study. Subjects were instructed to sit on a chair and rotate their head to the opposite side of the recording muscle. The VEMPs was recorded using 500 Hz STB and then click sound stimuli to each ear. The p13 and n23 latencies, p13-n23 peak-to-peak amplitude and VEMPs thresholds were obtained for further analysis. The VEMP responses were present in all subjects for STB and ware not recorded in one subject for click. The latencies of p13 and n23 of STB-VEMP were significantly longer, and the p13-n23 amplitudes were significantly greater for STB-VEMP [p < 0.05], and thresholds were higher for clicks [p < 0.05]. No significant difference was obtained between both ears and genders. [p > 0.05]. The VEMP responses were significantly different between the stimuli of STB and click, and the norms of different stimuli should be established for clinical interpretations. According to these data, we recommend STB stimuli in comparison with clicks for clinical diagnosis

Auditory neuropethy: a case of auditory neuropathy after hyperbilirubinemia

Auditory neuropathy is an hearing disorder in which peripheral hearing is normal, but the eighth nerve and brainstem are abnormal. By clinical definition, patient with this disorder have normal OAE, but exhibit an absent or severely abnormal ABR. Auditory neuropathy was first reported in the late 1970s as different methods could identify discrepancy between absent ABR and present hearing threshold. Speech understanding difficulties are worse than can be predicted from other tests of hearing function. Auditory neuropathy may also affect vestibular function. This article presents electrophysiological and behavioral data from a case of auditory neuropathy in a child with normal hearing after bilirubinemia in a 5 years follow-up. Audiological findings demonstrate remarkable changes after multidisciplinary rehabilitation. auditory neuropathy may involve damage to the inner hair cells-specialized sensory cells in the inner ear that transmit information about sound through the nervous system to the brain. Other causes may include faulty connections between the inner hair cells and the nerve leading from the inner ear to the brain or damage to the nerve itself. People with auditory neuropathy have OAEs response but absent ABR and hearing loss threshold that can be permanent, get worse or get better

[Auditory site of lesion in infants suffering from hyperbilirubinemia by using ABR and TEOAE]

Hyperbilirubinemia is one of the most common abnormalities during the neonatal period. Approximately 60% full-term and 80% preterm neonates suffer from hyperbilirubinemia. Hearing loss is one of the most prevalent side-effects of hyperbilirubinemia. This happens when the serum concentration of indirect bilirubin increases dramatically. The main purpose of this study is to evaluate the hearing status and to diagnose the probable site of lesion in affected children. In this cross-sectional study, 33 newborn to two year old subjects suffering from hyperbilirubinemia were evaluated using auditory brainstem response [ABR] and transient evoked otoacoustic emissions [TEOAE] tests In the Audiology department of the Faculty of Rehabilitation Sciences Iran University of Medical Sciences sampling method was accessible. 21% of the subjects had severe to profound hearing loss and 9% of subjects had mild to moderate hearing loss. In 15% of the subjects there was no response to ABR and TEOAE tests indicating cochlear and/or retrocochlear lesion. The other 15% manifest only abnormal ABR test indicating the presence of the auditory neuropathy. TEOAE test has its own limitations in these subjects, that is the hearing status of such patients can not be completely evaluated by using just TEOAE test. Therefore, to detect hearing loss both ABR and TEOAE tests must be performed in these subjects