Changes In Auditory Brainstem Response Research Articles

The quantification and mRNA expression levels of cochlear synapses in C57BL/6j mice following repeated exposure to noise.

This study aimed to examine the impact of repeated noise exposure on the quantification and mRNA expression levels of cochlear synapses. Measurements were conducted at baseline, 1 day, and 14 days post-exposure to 88 or 97 dB SPL noise (2 h/day for 7 days, frequency range 2-20 kHz). Auditory brainstem responses (ABRs), immunofluorescence and quantitative real-time PCR (qRT-PCR) were used to examine the results. 1. Exposure to 88 dB SPL caused minimal changes in ABRs, ribbon morphology and medial olivocochlear (MOC) efferent synapses; elevation of synaptophysin(SYP) and α9α10 nAchR mRNA levels were observed. 2. Exposure to 97 dB SPL caused threshold shift and synaptopathy of ribbon and MOC; downregulation of α10nAchR, SYP and ctbp2 mRNA levels were observed. Noise-induced cochlear synaptic degeneration involves both afferent and efferent synaptopathy.

Microneedle-Mediated Delivery of siRNA via Liposomal-Based Transfection for Inner Ear Gene Therapy.

Microneedle-mediated intracochlear injection of siRNA-Lipofectamine through the round window membrane (RWM) can be used to transfect cells within the cochlea. Our laboratory has developed 100-μm diameter hollow microneedles for intracochlear injection through the guinea pig RWM. In this study, we test the feasibility of microneedle-mediated injection of siRNA and Lipofectamine, a commonly used reagent with known cellular toxicity, through the RWM for cochlear transfection. Fluorescently labeled scramble siRNA was diluted into Lipofectamine RNAiMax and OptiMEM. One microliter of 5 μM siRNA was injected through the RWM of Hartley guinea pigs at a rate of 1 μl/min (n = 22). In a control group, 1.0 μl of Lipofectamine, with no siRNA, was diluted into OptiMEM and injected in a similar fashion (n = 5). Hearing tests were performed before and either at 24 hours, 48 hours, or 5 days after injection. Afterward, animals were euthanized, and cochleae were harvested for imaging. Control cochleae were processed in parallel to untreated guinea pigs. Fluorescence, indicating successful transfection, was observed within the basal and middle turns of the cochlea with limited distribution in the apex at 24 and 48 hours. Signal was most intense in the organ of Corti, spiral ligament, and spiral ganglion. Little to no fluorescence was observed at 5 days post-injection. No significant changes in auditory brainstem response (ABR) were noted post-perforation at 5 days, suggesting that siRNA-Lipofectamine at low doses does not cause cochlear toxicity. Small volumes of siRNA and Lipofectamine can be effectively delivered to cochlear structures using microneedles, paving the way for atraumatic cochlear gene therapy.

Factors influencing auditory brainstem response changes in infants

BackgroundTo elucidate the factors influencing auditory brainstem response (ABR) threshold improvement in infants. MethodsThis retrospective study included 626 infants who underwent ABR at the our Health and Medical Center between 2016 and 2020. Preliminary assessment indicated that 352 infants had an ABR threshold ≥40 dBnHL in both ears. A second ABR examination was conducted 5 months after delivery. The participants were divided into the improved (improvement ≥20 dBnHL) and unchanged (improvement <20 dBnHL) groups. The associations between risk factors were evaluated. Furthermore, we measured and compared the latencies of waves I, III, and V between participants with normal hearing and those in the improved and unchanged groups. ResultsThe improved and unchanged groups consisted of 185 and 167 participants, respectively. ABR deterioration occurred in one infant with unilateral congenital cytomegalovirus-associated hearing loss. Binary logistic regression analysis revealed that the presence of otitis media with effusion and Down syndrome were factors contributing to ABR threshold improvement. In the ABR waveform analysis, patients in the improved group who had otitis media with effusion exhibited prolonged latencies of waves I, III, and V. Conversely, patients in the unchanged group who had Down syndrome showed shortened I–V interval. ConclusionsHalf of the infants tested the second time showed improvement in ABR threshold. Children with congenital syndromes (such as Down syndrome) or otitis media with effusion should undergo a second ABR examination or other auditory assessments to ensure an accurate diagnosis of hearing loss.

Dolphin short-term auditory fatigue and self-mitigation.

Auditory brainstem responses (ABRs) were measured at 57 kHz in two dolphins warned of an impending intense tone at 40 kHz. Over the course of testing, the duration of the intense tone was increased from 0.5 to 16 s to determine if changes in ABRs observed after cessation of the intense sound were the result of post-stimulatory auditory fatigue or conditioned hearing attenuation. One dolphin exhibited conditioned hearing attenuation after the warning sound preceding the intense sound, but little evidence of post-stimulatory fatigue after the intense sound. The second dolphin showed no conditioned attenuation before the intense sound, but auditory fatigue afterwards. The fatigue was observed within a few seconds after cessation of the intense tone: i.e., at time scales much shorter than those in previous studies of marine mammal noise-induced threshold shifts, which feature measurements on the order of a few minutes after exposure. The differences observed between the two individuals (less auditory fatigue in the dolphin that exhibited the conditioned attenuation) support the hypothesis that conditioned attenuation is a form of "self-mitigation."

Effect of Electromagnetic Radiation from Mobile Phones on Auditory Brainstem Response.

Mobile phones are being used by around 70% of the global population. A simple non-invasive procedure to detect early impairment of the acoustic nerve and auditory pathway is by auditory brainstem response (ABR). It's a response to the sound stimulus generated from the brainstem in the form of electrical impulses. To determine the effect of long-term usage of mobile phones on auditory brainstem responses (ABRs). This Epidemiological, cross-sectional study was undertaken at a tertiary care hospital and includes 865 individuals aged between 18 to 45years using mobile phone for > 2years. Users were categorized into various groups according to the minutes of mobile usage per day, years of mobile usage and total duration of mobile phone use in dominant (mobile using) and non-Dominant (non-mobile using) ears. The changes in ABR were studied in each ear to ascertain the effect of EMF exposure due to chronic mobile phone use. Mean age of subjects was 27.01years. (M: F = 1.57:1.0). Range of mobile phone usage was from 4 to 900min/day, with mean as 85.94min/day. No significant differences were seen between dominant and non-dominant ears in regard to amplitudes of wave I, III and V, latencies of wave I and V and Inter peak latency (IPL) of wave I-III, III-V and I-V. No statistically significant difference for I-III, III-V and I-V IPL were found b/w two groups/ears except for usage of mobile phone for > 180min/day in wave I-V, usage for 0-4years in wave I-III and I-V and net hours usage for > 1500h in wave I-V. The mean IPL in all the waves increases with the increase in years of mobile usage and is maximum in all waves in > 12years mobile users. The long-term exposure to EMF does induce measurable changes in ABRs. Amplitude and IPLs of ABR were found comparable between the dominant and non-dominant ears using mobile phones, except for those using mobile usage for > 180min/day and with increasing years of usage of mobile phone. Therefore, prudent use of mobile phone should be encouraged for a shorter period of time and for essential purpose only.

Visualizing Contralateral Suppression of Hearing Sensitivity via Acoustic and Electric Brainstem Audiometry in Bimodal Cochlear Implant Patients: A Feasibility Study

Introduction: The medial olivocochlear reflex (MOCR) is a part of the binaural processing strategies and influences the efferent auditory pathway in normal-hearing individuals. Patients with asymmetric hearing loss often benefit from a bimodal hearing solution with a cochlear implant (CI) and a hearing aid (HA). However, hearing performances may vary with some surprisingly high- or low-performing CI/HA users. A potential role of the MOCR among these patients warrants further investigation. Otoacustics emissions are an established method to visualize the reflex; however, this technique implies some disadvantages. To visualize the MOCR via auditory brainstem response (ABR) could be a promising alternative. Methods: Twenty-three bimodal CI/HA users were enrolled. Experimental setup was as follows: I. electrical ABR on the CI side was recorded with and without simultaneous contralateral noise signal at the HA side, II. acoustic ABR was recorded on the HA side with and without simultaneous contralateral noise at the CI side. Brainstem thresholds and amplitudes of waveforms I–V with and without contralateral noise were compared. Potential correlations of patient-related factors and hearing performances were analysed. Results: In four individuals, a reduction of brainstem audiometry thresholds could be observed at the acoustic brainstem audiometry. In these cases, results could be reproduced. Summarizing ABR measurements at the HA side of all individuals, no relevant changes of ABR thresholds (dB nHL) or waveform amplitude reductions (nV) could be observed irrespective of the presence or absence of a contralateral suppression signal. Conclusion: Threshold changes of acoustic ABR upon presentation of a contralateral suppression signal could not generally be measured in bimodal CI users. However, in a subgroup, a highly reproducible effect was demonstrated if a contralateral suppression signal was applied. A reactivated rather than rehabilitated MOCR may have accounted for this effect in this subgroup. One could speculate that in these patients, bimodal fitting could be affected by the MOCR efferents.

Electroacupuncture Promotes Neuroplasticity of Central Auditory Pathway: An Auditory Evoked Potentials Study.

Our previous studies found that electroacupuncture at the right Zhongzhu acupoint (TE3) can enhance auditory recovery in rats with noise-induced hearing loss. Here, we investigated the changes in auditory brainstem response (ABR) and long late latency (LLR) evoked potential to explain the mechanisms of electroacupuncture at TE3. The auditory evoked potentials were recorded, including ABR and LLR, at baseline and on day 3 (D3), D5, and D8 after baseline. The 2-Hz electroacupuncture at the right TE3 was applied on D3, D4, and D5 in the electroacupuncture group but not in the control group. In ABR, compared with the control group, the latency shift of waves I (0.298 ± 0.033 vs -0.045 ± 0.057 ms), III (0.718 ± 0.038 vs -0.163 ± 0.130 ms), and V (1.160 ± 0.082 vs -0.207 ± 0.138 ms) on D3 (all p < 0.01) and of wave V (0.616 ± 0.433 vs -0.352 ± 0.209 ms, p < 0.05) on D5 was greater in the electroacupuncture group than that in the control group. Moreover, the interpeak latency shift of I-III (0.420 ± 0.041 vs -0.118 ± 0.177 ms) and I-V (0.863 ± 0.088 vs -0.162 ± 0.156 ms) on D3 (both p < 0.05) and of III-V (0.342 ± 0.193 vs -0.190 ± 0.110 ms) and I-V (0.540 ± 0.352 vs -0.343 ± 0.184 ms) on D5 (both p < 0.05) was greater in the electroacupuncture group than that in the control group. In LLR, the latency shift of P0 was greater in the electroacupuncture group than in the control group on D3 (3.956 ± 2.975 vs -1.178 ± 1.358 ms, p < 0.01) and D5 (2.200 ± 1.889 vs -0.311 ± 1.078 ms, p < 0.05). These findings indicate that electroacupuncture at the right TE3 can modulate the neuroplasticity of the central auditory pathway, including the brain stem and the primary and secondary auditory cortex.

Oral Valganciclovir Therapy in Infants Aged ≤2 Months with Congenital Cytomegalovirus Disease: A Multicenter, Single-Arm, Open-Label Clinical Trial in Japan.

Our aims were to determine the clinical impact of oral valganciclovir (VGCV) in infants aged ≤2 months with congenital cytomegalovirus (CMV) disease and evaluate the efficacy of VGCV when initiated beyond the neonatal period. The multicenter, single-arm, open-label clinical trial was conducted in Japan. Twenty-five infants aged ≤2 months with congenital CMV disease involving the central nervous system were enrolled and treated with VGCV for 6 months. The primary endpoint was the change in the whole blood CMV load before and after treatment. The secondary endpoint was the change in the auditory brainstem response (ABR) before and after treatment. Changes in ABR were assessed between the younger and older age groups (≤ and >30 days at treatment initiation). Of the 25 patients, one was excluded owing to epilepsy before VGCV administration. The median change in the CMV DNA level in whole blood was −246.0 IU/mL. The best ear and total ear assessments based on ABR were categorized as (improved + unchanged) after treatment for 100% and 93.8%, respectively. No differences in hearing efficacy were observed between the younger and older age groups. Oral VGCV is a potential therapeutic option for treating infants aged ≤2 months with congenital CMV disease.

Click-evoked auditory brainstem responses (ABRs) are intact in schizophrenia and not sensitive to cognitive training

Patients with schizophrenia have impairments in early auditory system functioning that relate to clinical, cognitive, and psychosocial functioning. Some neurophysiological biomarkers of auditory information processing are sensitive to and predictive of clinically relevant outcomes following auditory-based targeted cognitive training (TCT) in schizophrenia. It is not known, however, whether schizophrenia patients show abnormalities at the earliest stage of sensory processing reflecting the integrity of the ascending auditory pathway at the level of the brainstem, or whether such abnormalities can serve as biomarkers. This study aimed to determine whether click-evoked auditory brainstem responses (click ABRs) are 1) abnormal in schizophrenia patients relative to healthy comparison subjects (HCS), 2) acutely sensitive to or predictive of TCT response, and 3) associated with clinically relevant symptoms. We also sought to determine whether 4) click ABRs show adequate psychometric reliability. Click ABRs were examined in 52 patients with schizophrenia and 32 HCS. Patients were randomized to either TCT ( n = 30), which comprised 30 h of training, or treatment as usual (TAU; n = 23). Patients showed intact click ABRs relative to HCS and click ABRs did not change significantly after 1 or 30 h of TCT. Exploratory analyses revealed modest relationships between click ABRs and baseline measures of positive symptoms and speech-in-noise perception; acute changes in ABRs were modestly related to improvements on measures of cognition independent of treatment. ABR measurements showed adequate internal consistency indicating their suitability for cross-sectional studies of individual differences, but poor test-retest reliability indicating poor suitability for clinical trials. In contrast to a growing literature demonstrating the utility of later cortical neurophysiological measures for translational research, the present findings indicate that brainstem-mediated responses are intact in schizophrenia and are not sensitive to or predictive of clinical changes in the context of TCT. These data provide guidance for establishing future neurophysiology-guided interventions in schizophrenia.

Effect of Maternal Age and Anaemia on Auditory Brainstem Response of Preterm Infants in a Tertiary Care Hospital of Kolkata, West Bengal: A Cross-sectional Study

Introduction: Adolescent pregnancy and maternal anaemia have a detrimental effect on infant growth and development. They are associated with greater risk of premature births and Low Birth Weight (LBW). Wave Interpeak Latencies (IPLs) of infant Auditory Brainstem Response (ABR) indicate the degree of maturation of brainstem auditory pathways among preterm infants. Previous studies indicated that preterm infants show prolonged wave Interpeak Latencies (IPLs). Whether maternal parameters like age and haemoglobin level contributes to the changes in infant ABR is debated. Aim: To study the effect of maternal age and anaemic status on Brainstem Evoked Response Audiometry (BERA) changes among preterm infants. Materials and Methods: An observational, descriptive study of cross-sectional design was undertaken in the Neurophysiology laboratory of Department of Physiology, RG Kar Medical College and Hospital, Kolkata from December 2019 to December 2022. Total of 119 mother-preterm infant dyads were included. Click BERA was performed on the babies aged between 3 months to 1 year. Absolute and IPLs of wave I,III and V were obtained. Mothers were assigned anaemic status {Haempglobin (Hb) level&lt;9gm/dL} based on the information in their antenatal card. Student’s t test, Fisher’s exact test, one way ANOVA test were used for data analysis. A p-value less than 0.05 was considered significant. Results: Out of 76 adolescent mothers (age between 10 to &lt;18 years), 43 (56.6%) were anaemic. Out of 43 adult mothers (with age ≥18 years), 33 (76.7%) were anaemic. Mothers were divided into four groups, namely adolescent anaemic (n=43) and adolescent non anaemic (n=33), adult anaemic (n=33) and adult non anaemic (n=10). Distribution of data with respect to education years, social class and occupation among four mothers’ group was comparable [p-value&gt;0.05]. Preterm infants born to both anaemic adult [Hedges g=2.51] and anaemic adolescent mothers [Hedges g=1.06] showed dyssynchronous shortening of wave latencies compared to non anaemic counterparts (p-value&lt;0.05). Magnitude of difference with respect to infant ABR for non anaemic adolescent mothers vs non anaemic adult counterparts was large [Hedge s g=1.05] with p-value&lt;0.05. While maternal anaemia showed either shortening or prolongation of IPLs, adolescent maternal age was related with prolongation of the wave I-V. Effect size of maternal anaemia on infant ABR was more than for adolescent maternal age. Conclusion: Maternal anaemia may exaggerate abnormal maturation of the brain stem pathways in preterm infants irrespective of maternal age.

EFFECTS OF AGMATINE ON ACOUSTIC STARTLE REFLEX AND AUDITORY SYSTEM IN RATS

Background: A polyamine, agmatine, has been proposed as a new neurotransmitter in the brain. Objective: The aim of this study was to evaluate the effects of acute and chronic agmatine treatment on the rat auditory system. Methods: Male Wistar albino rats weighing between 280-330 grams were used. Animals were divided into four groups (n= 8 for each group). Acute and chronic agmatine (160 mg/kg) was administered to rats. Prepulse inhibition (PPI) of the acoustic startle reflex (ASR), distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABR) were evaluated in all groups. Results: Both acute and chronic agmatine treatments also significantly disrupted PPI. Chronic but not acute treatment with agmatine produced some DPOAE and ABR changes in rats. Conclusion: Our results suggested that chronic agmatine treatment for seven days resulted in some significant negative changes in cochlear function. Because the PPI of the ASR is also used as an indicator for psychoses, such as schizophrenia, in human and experimental animal studies, our findings also imply that the DPOAE and ABR tests may also be considered in the diagnosis and follow-up of patients with psychoses.

Hidden hearing loss is associated with loss of ribbon synapses of cochlea inner hair cells.

The present study aimed to observe the changes in the cochlea ribbon synapses after repeated exposure to moderate-to-high intensity noise. Guinea pigs received 95 dB SPL white noise exposure 4 h a day for consecutive 7 days (we regarded it a medium-term and moderate-intensity noise, or MTMI noise). Animals were divided into four groups: Control, 1DPN (1-day post noise), 1WPN (1-week post noise), and 1MPN (1-month post noise). Auditory function analysis by auditory brainstem response (ABR) and compound action potential (CAP) recordings, as well as ribbon synapse morphological analyses by immunohistochemistry (Ctbp2 and PSD95 staining) were performed 1 day, 1 week, and 1 month after noise exposure. After MTMI noise exposure, the amplitudes of ABR I and III waves were suppressed. The CAP threshold was elevated, and CAP amplitude was reduced in the 1DPN group. No apparent changes in hair cell shape, arrangement, or number were observed, but the number of ribbon synapse was reduced. The 1WPN and 1MPN groups showed that part of ABR and CAP changes recovered, as well as the synapse number. The defects in cochlea auditory function and synapse changes were observed mainly in the high-frequency region. Together, repeated exposure in MTMI noise can cause hidden hearing loss (HHL), which is partially reversible after leaving the noise environment; and MTMI noise-induced HHL is associated with inner hair cell ribbon synapses.

Grasshopper mice alter vocalizations with age-related and noise-induced hearing loss

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing pathologies, few studies have assessed vocal changes that co-occur with hearing deterioration. Northern grasshopper mice represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity for pure tone stimuli, with males losing hearing more rapidly than females. Mice experienced severe hearing loss across all frequencies after exposure to noise. Frequency and duration of long-distance vocalizations were affected by hearing loss similar to findings in other mammals. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.

Age‐related and noise‐induced hearing loss alters grasshopper mouse (Onychomys) vocalizations

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing loss, few studies have assessed vocal changes after acoustic trauma. Northern grasshopper mice (Onychomys leucogaster) represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses (ABRs) and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity across 4–32 kHz, with males losing hearing more rapidly than females. In addition, noise-exposed mice had a 61.55 dB SPL decrease in ABR sensitivity following a noise exposure, with some individuals exhibiting a 21.25 dB recovery 300–330 days after noise exposure. We also found that older grasshopper mice produced calls with lower fundamental frequency. Sex differences were measured in duration of calls with females producing longer calls with age. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.

Perinatal Epidermal Growth Factor Signal Perturbation Results in the Series of Abnormal Auditory Oscillations and Responses Relevant to Schizophrenia

Abstract Auditory neurophysiological responses, such as steady-state responses, event-related potential P300/P3, and phase-amplitude coupling, are promising translational biomarkers for schizophrenia, but their molecular underpinning is poorly understood. Focusing on ErbB receptor signals that are implicated in both schizophrenia and auditory processing/cognition, we explored the causal biological links between ErbB signals and these auditory traits with an experimental intervention into rats. We peripherally challenged rat pups with one of the amniotic ErbB ligands, epidermal growth factor (EGF), and characterized its consequence on the series of these auditory electrocorticographic measures. Auditory brainstem responses (ABRs) and cortical ON responses were also assessed under anesthesia to estimate the influence of higher brain regions. An auditory steady-state paradigm revealed attenuation of spectral power and phase synchrony to 40-Hz stimuli in EGF-challenged rats. We observed a reduction in duration mismatch negativity-like potentials and a delay of P3a responses, all of which are relevant to the reported auditory pathophysiological traits of patients with schizophrenia. Moreover, the perinatal EGF challenges resulted in enhanced theta-alpha/beta and theta-gamma coupling within the auditory cortex and changes in ABRs. However, the EGF challenges retained the normal ranges of cortical ON responses, potentially ruling out their fundamental auditory deficits. Perinatal exposure of an ErbB ligand to rats strikingly reproduced the whole series of aberrant auditory responses and oscillations previously reported in patients with schizophrenia. Accordingly, these findings suggest that developmental deficits in ErbB/EGF signaling might be involved in the auditory pathophysiology associated with schizophrenia.

Analysis of Auditory Brainstem Response Change, according to Tinnitus Duration, in Patients with Tinnitus with Normal Hearing.

The purpose of this study was to analyze auditory brainstem response (ABR) waveforms of patients with tinnitus with normal hearing, according to tinnitus duration, and demonstrate the possible pathophysiological mechanisms of tinnitus. From January 2016 to December 2017, patients who presented to our hospital with tinnitus as their chief complaint were enrolled and reviewed retrospectively. Pure tone audiometry and ABR tests were performed. The patients were classified into three groups according to tinnitus duration: acute (<1 month), subacute (1-6 months), and chronic (>6 months). The amplitudes of waves I and V and the latencies of waves I, III, and V were evaluated. In this study, 177 ears of 128 patients with tinnitus with normal hearing were evaluated. Wave V amplitude was significantly lower during the subacute phase than during the acute phase. The absolute latency value of wave V was greater during the subacute phase than during the acute phase. The interpeak latency I-V was significantly prolonged during the subacute phase compared with the acute and chronic phases. Wave V amplitude, wave V absolute latency, and interpeak latency I-V varied significantly between cases with a 1-month and 6-month tinnitus history. The compensatory response to tinnitus decreased sharply after 1 month of symptoms. Early tinnitus identification and treatment initiation are recommended.

Within-Subject Analysis of Auditory Brain Stem Responses in Adults With Unilateral Tinnitus.

Tinnitus affects about 10% of population worldwide. Most patients present with some degrees of hearing impairment, while others remain normal. The aim of this study was to analyze the latency and amplitude of auditory brain stem response (ABR) waveforms in patients with unilateral tinnitus. The tinnitus ears and non-tinnitus ears were compared for each patient. Sixty-seven patients with single-sided tinnitus were enrolled, including 26 male and 41 female patients with a mean age of 54.4 (age ranged from 22 to 79). Eighteen patients had bilateral normal hearing, while 49 patients had some degree of sensorineural hearing. The ABR waveforms were retrospectively analyzed in terms of waves I, III, and V absolute latency, as well as waves I-III, waves II-V, and waves I-V latency intervals, amplitude, and amplitude ratio (III/I, V/I). Statistical analyses were performed within patients. There was no significant ABR difference between the tinnitus and non-tinnitus ears with regard to all the wave latencies and amplitudes in our patients (all P values >0.1). Our result that ABR changes were not found between tinnitus and non-tinnitus ears implies that tinnitus does not simply originate from the defect of the peripheral auditory system. It conforms to the contemporary theory that a higher level of the brain is involved in the generation of tinnitus.

A study of auditory brainstem evoked responses in type 1 and type 2 diabetes mellitus patients with normal hearing

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Diabetes mellitus (DM) is one of the most common metabolic disorders with millions of cases world-wide. Its effect on functioning of the central nervous system (CNS) and the peripheral nerves is a matter of current neurological research. Our study aimed to find out changes in auditory brainstem responses if any, in patients with type 1 and type 2 DM patients with apparently normal hearing.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; 50 cases each of type 1 and type 2 diabetic patients with normal hearing were chosen along with 50 healthy controls. Pure tone audiometry and brainstem evoked response audiometry (BERA) was performed in all cases. The BERA results were interpreted for the latencies of waves I, II, III, IV and V and inter-peak latencies I-III, I-V and III-V. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Significant delay in absolute latency of wave I, III, IV, V and inter-peak latencies I-V and III-V was seen in Type 1 diabetic patients. In Type 2 diabetic patients, latencies of waves I, II, III, IV and V and inter-peak latencies I-III, I-V and III-V were significantly delayed. There was no statistically significant difference in latency delay between type 1 and type 2 DM. No relation was found with the duration of DM.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; BERA is a non-invasive and easy to perform test that can detect minor CNS changes and can be used to detect peripheral (auditory nerve) and central neuropathy in diabetics even in absence of clinical signs and symptoms of deafness.&lt;/p&gt;

Changes in Auditory Brainstem Response in very preterm and late preterm infants

AimAim of this study was to compare the absolute and interpeak latencies of Auditory Brainstem Responses (ABR) in very preterm and late preterm infants at 1 month and 3 months of corrected age. Methodology: ABR traces were obtained from 80 preterm infants (40 very preterm and 40 late preterm) at 1 month and 3 months of corrected age in a prospective, comparative cohort study. Auditory click stimuli at 70 dBnHL and 30 dBnHL, with repetition rate of 11.1/s were used. Absolute latencies of peak I, III, V and interpeak latencies of peak I-V, I-III and III-V were analyzed and compared between preterm groups at 1 month and 3 months of corrected age. Wilcoxon Signed Ranks test was used to compare the ABR variables. Mann Whitney test was used to make inferences between groups. ResultsThere was a statistically significant difference in absolute latencies and interpeak latencies between very preterm and late preterm infants at 1 month of corrected age (p < 0.05). Absolute latency of peak I was similar among both groups of preterms. Absolute latencies of peak III, V and interpeak latencies I-III, III-V and I-V were prolonged in very preterm infants at 1 month of corrected age. However, these latencies were significantly reduced at 3 months of corrected age. This indicated accelerated maturation/myelination of the central auditory nervous system in very preterm infants. Absolute latencies of peak III and V and interpeak interval I-V was reduced in late preterm infants at 3 months of corrected age and this was statistically significant. This reduction in latency was considered to be a normal age dependent change. ConclusionFindings of the current study revealed that there was no deviation in the pattern of auditory maturation among preterms; it followed the typical ‘caudal to rostral’ form of maturation. Very preterm infants have less mature neuronal development compared with late preterm infants at 1 month of corrected age which catches up at 3 months of corrected age.

Effects of transient auditory deprivation during critical periods on the development of auditory temporal processing

ObjectivesThe central auditory pathway matures through sensory experiences and it is known that sensory experiences during periods called critical periods exert an important influence on brain development. The present study aimed to investigate whether temporary auditory deprivation during critical periods (CPs) could have a detrimental effect on the development of auditory temporal processing. Materials and methodsTwelve neonatal rats were randomly assigned to control and study groups; Study group experienced temporary (18–20 days) auditory deprivation during CPs (Early deprivation study group). Outcome measures included changes in auditory brainstem response (ABR), gap prepulse inhibition of the acoustic startle reflex (GPIAS), and gap detection threshold (GDT). To further delineate the specific role of CPs in the outcome measures above, the same paradigm was applied in adult rats (Late deprivation group) and the findings were compared with those of the neonatal rats. ResultsSoon after the restoration of hearing, early deprivation study animals showed a significantly lower GPIAS at intermediate gap durations and a larger GDT than early deprivation controls, but these differences became insignificant after subsequent auditory inputs. Additionally, the ABR results showed significantly delayed latencies of waves IV, V, and interpeak latencies of wave I-III and wave I-V in study group. Late deprivation group didn't exhibit any deterioration in temporal processing following sensory deprivation. ConclusionTaken together, the present results suggest that transient auditory deprivation during CPs might cause reversible disruptions in the development of temporal processing.