Longitudinal auditory pathophysiology following mild blast-induced trauma.

Blast-induced hearing difficulties affect thousands of veterans and civilians. The long-term impact of even a mild blast exposure on the central auditory system is hypothesized to contribute to lasting behavioral complaints associated with mild blast traumatic brain injury (bTBI). Although recovery from mild blast has been studied separately over brief or long time windows, few, if any, studies have investigated recovery longitudinally over short-term and longer-term (months) time windows. Specifically, many peripheral measures of auditory function either recover or exhibit subclinical deficits, masking deficits in processing complex, real-world stimuli that may recover differently. Thus, examining the acute time course and pattern of neurophysiological impairment using appropriate stimuli is critical to better understanding and intervening in bTBI-induced auditory system impairments. Here, we compared auditory brainstem response, middle-latency auditory-evoked potentials, and envelope following responses. Stimuli were clicks, tone pips, amplitude-modulated tones in quiet and in noise, and speech-like stimuli (iterated rippled noise pitch contours) in adult male rats subjected to mild blast and sham exposure over the course of 2 mo. We found that blast animals demonstrated drastic threshold increases and auditory transmission deficits immediately after blast exposure, followed by substantial recovery during the window of 7-14 days postblast, although with some deficits remaining even after 2 mo. Challenging conditions and speech-like stimuli can better elucidate mild bTBI-induced auditory deficit during this period. Our results suggest multiphasic recovery and therefore potentially different time windows for treatment, and deficits can be best observed using a small battery of sound stimuli.NEW & NOTEWORTHY Few studies on blast-induced hearing deficits go beyond simple sounds and sparsely track postexposure. Therefore, the recovery arc for potential therapies and real-world listening is poorly understood. Evidence suggested multiple recovery phases over 2 mo postexposure. Hearing thresholds largely recovered within 14 days and partially explained recovery. However, midlatency responses, responses to amplitude modulation in noise, and speech-like pitch sweeps exhibited extended changes, implying persistent central auditory deficits and the importance of subclinical threshold shifts.

The role of auditory evoked potentials and otoacoustic emissions in early detection of hearing abnormalities in Behçet's disease patients. A case control study.

OBJECTIVES: To determine the types and to assess the role of auditory evoked potentials and otoacoustic emissions in early detection of hearing abnormalities in Behçet's disease (BD) patients. Their correlations with disease activity were also considered. METHODS: Thirty patients with BD and thirty apparently sex- and age-matched healthy volunteers were included in this study. Auditory evaluation included pure tone audiometry (PTA), otoacoustic emissions (TEOAEs, DPOAE), auditory brainstem response test (ABR) and cortical auditory evoked potentials (tone and speech CAEPs) for all patients and control. RESULTS: The highest abnormality of CAEP latencies elicited by (500Hz and 1000 Hz) as well as speech stimuli (da and ga) among our BD patients was delayed P1 and N1 waves at 80 dB with greater bilateral affection, as well as significant differences between patients and controls. All our BD patients had a smaller amplitude of distortion product OAE (DPOAE) and S/N ratio at 1, 2, 4, 6 kHZ compared with controls and the differences were highly statistically significant (p=0.0001). CONCLUSIONS: Being one of the autoimmune inner ear diseases (AIED), BD has a definite hearing impairment, even in the presence of normal hearing sensitivity, as evidenced by PTA. BD patients had a sub-clinical cochlear pathology which was not affected by disease activity or different organ affection. DPOAE (S/N ratio) proved to be a sensitive test in detecting minimal changes in cochlear pathology and the latencies of CAEPs (tone and speech) measures were considered as sensitive indicators (100%) of early detection of hearing impairment in BD patients.

The effect of audiovisual distraction on the tolerability of flexible bronchoscopy: a randomized trial.

OBJECTIVE: It is important to minimize patient discomfort during invasive diagnostic and therapeutic procedures such as bronchoscopy. The aim of this study was to investigate the effect of audiovisual distraction on the tolerability of flexible bronchoscopy (FB). MATERIALS AND METHODS: We conducted a prospective, randomized, controlled trial on patients undergoing FB at a hospital in Zahedan, Iran, in 2015. The patients were equally and randomly divided into a control group and an experimental group. Patients in the control group received standard care during FB While patients in the experimental group selected familiar folk music that was played during the procedure along with the screening of images of nature. The duration of the FB was recorded and cough, dyspnea, choking, nausea and pain were evaluated using a visual analogue scale before and after the procedure. Statistical analysis was carried out using paired and independent t-tests, χ2 -tests and analysis of covariance. RESULTS: Sixty patients met the inclusion criteria and were randomized. The duration of the FB procedure was significantly shorter in the experimental group compared with the control group (mean ± standard deviation 7.87 ± 2.12 min and 10.27 ± 1.72 min, respectively; P < 0.05). Dyspnea, cough and pain were significantly less severe in the experimental group compared with the control group (P < 0.05), but choking and nausea were not significantly different between the two groups (P > 0.1). CONCLUSIONS: Our findings showed that audiovisual distraction had a positive effect on the tolerability of FB. This method has important potential as a simple and practical approach in reducing discomfort during invasive diagnostic and treatment procedures.

Spiral ganglion degeneration and hearing loss as a consequence of satellite cell death in saposin B-deficient mice.

Saposin B (Sap B) is an essential activator protein for arylsulfatase A in the hydrolysis of sulfatide, a lipid component of myelin. To study Sap B's role in hearing and balance, a Sap B-deficient (B(-/-)) mouse was evaluated. At both light and electron microscopy (EM) levels, inclusion body accumulation was seen in satellite cells surrounding spiral ganglion (SG) neurons from postnatal month 1 onward, progressing into large vacuoles preceding satellite cell degeneration, and followed by SG degeneration. EM also revealed reduced or absent myelin sheaths in SG neurons from postnatal month 8 onwards. Hearing loss was initially seen at postnatal month 6 and progressed thereafter for frequency-specific stimuli, whereas click responses became abnormal from postnatal month 13 onward. The progressive hearing loss correlated with the accumulation of inclusion bodies in the satellite cells and their subsequent degeneration. Outer hair cell numbers and efferent function measures (distortion product otoacoustic emissions and contralateral suppression) were normal in the B(-/-) mice throughout this period. Alcian blue staining of SGs demonstrated that these inclusion bodies corresponded to sulfatide accumulation. In contrast, changes in the vestibular system were much milder, but caused severe physiologic deficits. These results demonstrate that loss of Sap B function leads to progressive sulfatide accumulation in satellite cells surrounding the SG neurons, leading to satellite cell degeneration and subsequent SG degeneration with a resultant loss of hearing. Relative sparing of the efferent auditory and vestibular neurons suggests that alternate glycosphingolipid metabolic pathways predominate in these other systems.

[The evaluation of the hearing function in the premature infants with intrauterine growth retardation during the third and sixth months of life by recording auditory steady-state response].

The objective of the present work was to study the function of the retrocochlear auditory pathway in the premature infants with intrauterine growth retardation (IGR) in comparison to that of the normotrophics of a similar gestational age during the third and sixth months of life by recording auditory steady-state responses (ASSR). The audiological examination by the method of auditory steady-state response (ASSR) involved 127 children at the 3d month of life and in 97 children at the 6th month of life. It was shown that the ASSR thresholds at certain frequencies during the 3d and 6th months of life of the children born after the 32d week of pregnancy were significantly higher than in the children born after 32 weeks gestation. The comparison of the two objective audiological methods, viz. distortion-product otoacoustic emission (DPOAE) and ASSR, indicates that both should be used to evaluate the hearing function during the third and sixth months of life to compensate for the discrepancy between the results obtained by either technique.

Distortion-product otoacoustic emissions and contralateral suppression findings in children with Asperger's Syndrome.

OBJECTIVES: Children with Asperger's Syndrome (AS) often demonstrate auditory behaviors such as hypersensitivity to sounds and poor performance in noisy environments. These auditory behaviors may be related to cochlear dysfunction and abnormal medial olivocochlear bundle (MOCB) activity. The objective of this study was to examine the distortion-product otoacoustic emissions (DPOAEs) with and without contralateral white noise to evaluate outer hair cell activity and MOCB activity in children with AS. METHODS: A case control study where 18 boys with AS and 18 age-matched control subjects participated in the study. For both groups, DPOAEs were recorded at 4031, 2627, 1969, and 1359 Hz f2 frequencies with and without contralateral white noise at 30 dB SL. DPOAE SNRs and difference scores were analyzed for possible differences between both groups and age subgroups (young and old children). RESULTS: In the quiet condition, there were no significant group or ear differences in DPOAEs SNR. However, DPOAEs SNR were larger at 4031 Hz than at lower frequencies in both groups, mostly due to negative effect of background noise on low frequency response. Contralateral noise resulted in both suppression and enhancement of the DPOAE SNRs in 93% of the control group and 90% of the AS group. However, there were no significant differences in suppression and enhancement between the two groups or age subgroups. The young controls had right ear advantage and significantly larger suppression at all frequencies except 4031 Hz than old controls. The young children with AS had slight left ear advantage and significantly larger suppression only at 2672 Hz compared to the old children with AS. CONCLUSIONS: The results, indicating minor differences in DPOAEs and contralateral suppression and enhancement of DPOAEs between both control and AS groups and age subgroups, suggest subtle differences in the function of the outer hair cells and the MOCB activity. Therefore, other central auditory processing in the temporal lobe, limbic system and autonomic nervous system may be involved in the generation of hypersensitivity to sounds and difficulty understanding in noisy environments in children with AS.

Auditory function in children with Charcot-Marie-Tooth disease.

The peripheral manifestations of the inherited neuropathies are increasingly well characterized, but their effects upon cranial nerve function are not well understood. Hearing loss is recognized in a minority of children with this condition, but has not previously been systemically studied. A clear understanding of the prevalence and degree of auditory difficulties in this population is important as hearing impairment can impact upon speech/language development, social interaction ability and educational progress. The aim of this study was to investigate auditory pathway function, speech perception ability and everyday listening and communication in a group of school-aged children with inherited neuropathies. Twenty-six children with Charcot-Marie-Tooth disease confirmed by genetic testing and physical examination participated. Eighteen had demyelinating neuropathies (Charcot-Marie-Tooth type 1) and eight had the axonal form (Charcot-Marie-Tooth type 2). While each subject had normal or near-normal sound detection, individuals in both disease groups showed electrophysiological evidence of auditory neuropathy with delayed or low amplitude auditory brainstem responses. Auditory perception was also affected, with >60% of subjects with Charcot-Marie-Tooth type 1 and >85% of Charcot-Marie-Tooth type 2 suffering impaired processing of auditory temporal (timing) cues and/or abnormal speech understanding in everyday listening conditions.

DPOAEs and contralateral acoustic stimulation and their link to sound hypersensitivity in children with autism.

OBJECTIVE: The hypersensitivity of children with autism to sound is a relatively unexplained behavior. The goal of the current study was to investigate the DPOAE characteristics of children with autism compared to a control group. DESIGN: DPOAEs with and without contralateral stimuli were measured in two groups in three different conditions. STUDY SAMPLE: The study employed 14 children with autism and a control group with 28 age-matched participants. RESULTS: In the without-contralateral stimulus condition, the overall S/N of DPOAEs was greater for the control group compared to the autism group (p < 0.0005). For both groups, the DPOAE S/N increased as a function of frequency in both ears. In the with contralateral stimulus condition, group and ear effects were noticed, however, no age, frequency, or contralateral stimulus type (BBN vs. 1000 Hz) effect could be detected. CONCLUSIONS: Presence of reduced DPOAEs in the autism group does not support the hypothesis that sound hypersensitivity in children with autism may be related to overactive outer hair cells function; rather it may be due to early cochlear dysfunction. Also, sound hypersensitivity in the autism group may be due to abnormality of the efferent auditory pathway as shown by lack of sufficient contralateral suppression.

Pseudohypacusis in childhood and adolescence is associated with increased gray matter volume in the medial frontal gyrus and superior temporal gyrus.

Pseudohypacusis is a somatoform disorder characterized by hearing loss with discrepancies between pure-tone audiometry and auditory brainstem response (ABR), but the underlying neuronal mechanisms remain unclear. Using voxel-based morphometry (VBM) with magnetic resonance (MR) imaging for 14 unmedicated, right-handed patients and 35 healthy control subjects, we investigated whether functional hearing loss was associated with discernible changes of brain morphology. Group differences in gray matter volume (GMV) were assessed using high-resolution, T1-weighted, volumetric MR imaging datasets (3T Trio scanner; Siemens AG) and analyzed with covariant factors of age, sex, socioeconomic status (SES), and total GMV, which was increased by 27.9% in the left medial frontal gyrus (MFG) (Brodmann area 10) (p=.001, corrected cluster level) and by 14.4% in the right superior temporal gyrus (STG) and the adjacent middle temporal gyrus (MTG) (BA42 to 21) (p=.009, corrected cluster level) in patients with pseudohypacusis. The GMV in the right STG (BA42) and verbal intelligence quotient (IQ) were correlated significantly with the Wechsler Intelligence Scale for Children - Third Edition (WISC-III) (ß=-.57, p<.0001) and level of SES (ß=-.55, p<.0001). The present findings suggest that the development of the auditory association cortex involved in language processing is affected, causing insufficient pruning during brain development. We therefore assert that differences in the neuroanatomical substrate of pseudohypacusis subjects result from a developmental disorder in auditory processing.

Evaluation of ear function after cardiopulmonary bypass with otoacoustic emissions: a pilot study.

OBJECTIVES: During extracorporeal circulation (ECC) there is a great hemodynamic stress with possible impact on the microcirculation, including cochlear one. Previous studies have evaluated the effect of ECC on inner ear with contrasting results. The aim of this study is to evaluate possible modifications of the outer hair cells (OHC) function after open heart surgery (OHS) under ECC with transient evoked (TEOAEs) and distortion product otoacoustic emissions (DPOAEs). METHODS: Ten patients (5 F and 5 M), undergoing OHS with ECC, were subjected to an audiological assessment pre- and postoperatively. We compared the pre-operative and post-operative mean auditory thresholds, mean TEOAEs reproducibility and amplitude, and mean DPOAEs amplitude. Student's t-test was used to compare different values. RESULTS: No significant differences were found between pre- and post-operative audiological assessment both in hearing level and in otoacoustic emissions. CONCLUSION: OHC function seems to be not affected by hemodynamic stress induced by ECC. Further studies on a larger scale will be necessary to confirm our preliminary data.

A neural network model of normal and abnormal auditory information processing.

The ability of the brain to attenuate the response to irrelevant sensory stimulation is referred to as sensory gating. A gating deficiency has been reported in schizophrenia. To study the neural mechanisms underlying sensory gating, a neuroanatomically inspired model of auditory information processing has been developed. The mathematical model consists of lumped parameter modules representing the thalamus (TH), the thalamic reticular nucleus (TRN), auditory cortex (AC), and prefrontal cortex (PC). It was found that the membrane potential of the pyramidal cells in the PC module replicated auditory evoked potentials, recorded from the scalp of healthy individuals, in response to pure tones. Also, the model produced substantial attenuation of the response to the second of a pair of identical stimuli, just as seen in actual human experiments. We also tested the viewpoint that schizophrenia is associated with a deficit in prefrontal dopamine (DA) activity, which would lower the excitatory and inhibitory feedback gains in the AC and PC modules. Lowering these gains by less than 10% resulted in model behavior resembling the brain activity seen in schizophrenia patients, and replicated the reported gating deficits. The model suggests that the TRN plays a critical role in sensory gating, with the smaller response to a second tone arising from a reduction in inhibition of TH by the TRN.

Cerumen removal: comparison of cerumenolytic agents and effect on cognition among the elderly.

Cerumen impaction may affect hearing and decrease hearing acuity, thus decreasing cognitive functions among the elderly. The objective of this study was to compare the safety and the efficacy of three cerumenolytic agents and to assess the effect of cerumen removal on cognition. Thirty eight elderly subjects (mean age: 78 years, total 76 ears) were treated with either Auro®, Cerumol® or the newer CleanEars®, and the change in the degree of ear canal occlusion was examined after a week. In addition, a change in cognition following cerumen removal was evaluated using Raven's standard progressive matrices (RSPM) test. There was no difference regarding the eventual degree of occlusion between the three treatment groups. Only in the CleanEars® group a complete resolution of obstruction in both ears was achieved. A statistically significant difference between the RSPM score before and after the removal of cerumen was found. Using CleanEars® is as effective and safe as other agents and may be advantageous due to its spray application. Removal of cerumen significantly improves the well-being of elderly patients.

Chronological changes in compromised olivocochlear activity and the effect of insulin in diabetic Wistar rats.

The aims of the present study were to investigate in diabetic rats: (1) the chronological changes of compromised medial olivocochlear bundle (MOCB) activity and auditory brainstem responses (ABR) and (2) the effect of insulin on diabetes-related hearing dysfunction. Diabetes mellitus was induced by intraperitoneal injection of streptozotocin. Thirty male Wistar rats were divided into three groups: control (C), diabetes with insulin injection (DI), and diabetes without insulin injection (DM). Click-evoked ABR, distortion product otoacoustic emission (DPOAE) and the contralateral suppression (CS) of DPOAE were measured for all animals monthly. Throughout the experiment, the thresholds of click-evoked ABR did not differ among groups. Wave III was delayed and interpeak latency I-III was prolonged in the DM group at the age of 29 weeks (p < 0.05). The amplitudes of the CS of DPOAE were markedly decreased after the 25th week in the DM group, but not in the C and DI groups. Compared to the C group, the CS in the DI group was not attenuated at any frequency. Dysfunction of auditory efferent olivocochlear activity developed in diabetic rats presenting no evidence of hearing loss. The finding of a significant decrease of the CS of DPOAE could be used as an earlier indicator of diabetes-related hearing impairment than changes of ABRs. The time course of compromised MOCB is positively correlated with the duration of diabetes. Insulin could therefore protect against compromised MOCB.

[NMDAR expression in the cochlear nucleus and hearing damage in neonatal rats with hyperbilirubinemia].

OBJECTIVE: To study the role of N-methyl-D-aspartate-receptor (NMDAR) expression in the development of hearing damage in neonatal rats with hyperbilirubinemia. METHODS: Sixty seven-day-old Sprague-Dawley rats were randomly injected with bilirubin of 100 microg/g (low-dose treatment group) or 200 microg/g (high-dose treatment group) or normal saline (control group). Auditory brainstem response (ABR) was examined. The concentrations of bilirubin in blood and brain were measured. NMDAR expression in the cochlear nucleus slices was examined by immunohistochemistry assay. RESULTS: ABR reflecting threshold obviously increased, and I, II and III wave latency as well as I-II, II-III and I-III interval were more prolonged in the two bilirubin treatment groups when compared with the control group. The NMDAR expression in the cochlear nucleuse in the two bilirubin treatment groups was obviously lower than that in the control group. The NMDAR expression in the cochlear nucleuse was negatively correlated with the brain bilirubin content and the ABR reflecting threshold in the two bilirubin treatment groups. CONCLUSIONS: An increased NMDAR activity may play an important role in hearing damage following hyperbilirubinemia.

Cochlear sources and otoacoustic emissions.

Current understanding suggests that there are two different mechanisms by which otoacoustic emissions (OAEs) are generated in the cochlea. These mechanisms include a nonlinear-distortion mechanism and a coherent-reflection mechanism. Distortion product OAEs (DPOAEs) are believed to include contributions from both mechanisms, while stimulus frequency OAEs (SFOAES), at least at low and moderate levels, are believed to be generated primarily by the coherent-reflection mechanism. In the case of DPOAEs, the interaction of the two mechanisms produces a series of alternating peaks and valleys in the response level when recorded in small frequency increments. This pattern of peaks and valleys typically is referred to as fine structure. There has been much speculation that the interaction of the two mechanisms and the resulting fine structure limits the clinical test performance of DPOAEs. There are few data to address this speculation. Here, we review the literature that describes the cochlear source mechanisms and their potential relationship to clinical applications. We then present results for preliminary data collected in a group of 10 normal-hearing subjects where we explore the influence of common approaches to setting DPOAE stimulus parameters on the resulting fine structure. These preliminary results suggest that, at the moderate stimulus levels used in clinical applications, each of the different stimulus parameters results in a similar amount of fine structure and, therefore, fine structure cannot be eliminated through manipulation of stimulus parameters. We also review the results of some preliminary efforts to identify stimulus parameters that can be used to record SFOAEs (OAEs generated by the reflection mechanism). The potential clinical applications of SFOAEs have received little attention in the literature. By identifying stimulus parameters producing robust responses in normal-hearing ears, it may be possible to more fully evaluate clinical applications of SFOAEs.

Cortical activation during a pitch discrimination task in tinnitus patients and controls--an fMRI study.

Chronic subjective tinnitus has been associated with aberrant activation of cortical areas involved in the perception of auditory information. This leads to the hypothesis that neural correlates of altered auditory perception may be found in tinnitus patients using functional magnetic resonance imaging. To study brain activation patterns due to acoustic stimulation in a pitch discrimination task, 6 tinnitus patients and 6 age-matched controls were investigated. Tones were presented binaurally at 5 beeps/s with three different frequencies in a block design. Using Statistical Parametrical Mapping, we found activation of secondary auditory areas in both groups. Furthermore, controls showed activation of the right-hemispheric anterior insula, whereas the middle frontal gyrus, putamen and left-hemispheric insula were activated in tinnitus patients. In the between-group analysis, activation of the caudate nucleus, superior frontal gyrus (Brodmann area 8) and cingular cortex was more pronounced in patients than in controls suggesting the perception of auditory inputs in a more emotional context in our patient group compared to controls.

[Efferent suppression test--sensitivity and specificity]. / Test eferentny slimaka--czulosc i swoistosc metody.

INTRODUCTION: The amplitude of click evoked otoacoustic emissions can be suppressed (reduced) with contralateral acoustic stimulation (CAS). This is thought to be due to the inhibitory control that the medial efferent auditory nerve exerts on outer hair cell function. One commonly used test of medial olivocochlear (MOC) function in humans involves measuring the degree of suppression of ipsilateral otoacoustic emissions (OAEs) by CAS. This effect is called contralateral suppression, efferent effect or olivocochlear reflex. Aim of the study. The objective of this study was to measure cut-off level of contralateral suppression, sensitivity and specificity of the efferent test. MATERIAL AND METHODS: To evaluate the function of MOC system click evoked otoacoustic emissions (CEOAEs) with and without continuous contralateral broadband noise (BBN) stimulation were recorded in 14 patients with multiple sclerosis, 16 patients with unilateral cerebello-pontine angle tumor and control group matched for age and gender. BBN was presented at 50 dB SL and otoacoustic emissions were recorded in response to nonlinear clicks at 70 +/- 3 dB SPL. RESULTS: The cut-off level was established at -1.4 dB. For 1.4 dB cut-off level of contralateral suppression the sensitivity of the efferent test was 90% and specificity was 70%. CONCLUSIONS: To conclude, assessment of efferent suppression may be a useful addition to the battery test employed in the investigation of multiple sclerosis and cerebello-pontine angle tumors. The MOC suppression test may provide a tool for an early diagnosis of the brainstem pathology.

Down syndrome: caring holistically in primary health care.

All primary health care should be underpinned with a firm theoretical knowledge. The holistic management of Down syndrome patients should be an integral part of this knowledge base. The application of this knowledge should ideally encompass a positive approach to empowering patients to lead healthy, active and normal lives. This article highlights a basic documentation of what 'Down syndrome' is. The article gives community nursing staff the opportunity to refresh their knowledge of the condition, then encourages critical reflection on professional practice within primary care, with the intention of raising skill and awareness for the holistic management of patients with Down syndrome.

Clinical characteristics of delayed endolymphatic hydrops: long-term results of hearing and efficacy of hyperbaric oxygenation therapy.

CONCLUSION: Diuretics significantly improved hearing in patients with contralateral-type DEH, whereas they did not inpatients with ipsilateral-type DEH. OBJECTIVE: We report a review of 26 cases of DEH treated in recent 6 years. PATIENTS AND METHODS: The study group comprised 22 contralateral and 4 ipsilateral types of DEH. The efficacy of diuretics on the improvement in hearing was examined quantitatively. The efficacy of hyperbaric oxygenation therapy (HBO) on hearing was examined in six patients. RESULTS: The general properties of these cases were similar to those reported previously, except for the high proportion of patients with contralateral-type DEH. Diuretics significantly improved the hearing of patients with contralateral-type DEH. In contrast, no significant improvement by diuretics was noted in ipsilateral-type DEH.