Acoustic Reflex Measurements Research Articles

Contralateral Suppression of Acoustic Reflex in Individuals with Chronic Subjective Tinnitus

Objectives: The first aim of this study is to determine whether subjective tinnitus has an effect on the medial olivocochlear bundle function in the auditory efferent system, with the contralateral acoustic reflex suppression test. The second aim is to contribute to the literature on the auditory efferent system. Materıals and Methods: The study included 20 individuals with chronic subjective tinnitus and 28 healthy controls. Acoustic reflex measurement was applied to both groups at 0.5, 1, and 2 kHz with and without contralateral noise. The contralateral suppression of the acoustic reflex (CSAR) results of both groups were compared in terms of CSAR threshold (CSART) and CSAR amplitude (CSARA). Results: There was no significant difference between the control and tinnitus groups in terms of CSART (P > 0.05), except that the left ear of the tinnitus group was higher than the control group at 0.5 kHz (P = 0.015). There was no significant difference in CSARA of the ears at all frequencies between the two groups (P > 0.05). Conclusion: These results suggest that the CSAR test can be used as a complementary test in the evaluation of the auditory efferent system of individuals with chronic subjective tinnitus.

Assessment of auditory functions in patients with hepatic glycogen storage diseases.

Hepatic glycogen storage diseases are a group of diseases manifesting mainly with hypoglycemia and hepatomegaly. The patients require frequent daytime and nocturnal feedings. Hypoglycemia may cause sensorineural hearing loss and nocturnal feeding is a risk factor for the development of gastroesophageal reflux that may cause chronic otitis media and hearing loss consequently. We aimed to determine the prevalence and characteristics of hearing loss in hepatic glycogen storage diseases. A total of 24 patients with hepatic glycogen storage disease (15 glycogen storage disease type I and 9 non type I) and 24 age/sex matched healthy controls were enrolled in the study. Pure tone audiometer, immitansmetry, acoustic reflex measurement, otoacoustic emission test (OAE) and auditory brainstem response (ABR) tests were applied to all participants. Hearing loss was determined in 17/24 patients (12 glycogen storage disease type I and 5 non type I) with pure tone audiometer. Interpretation of all the findings revealed a total of 8 patients had conductive and 9 had mixed hearing loss. All parameters were significantly different than the control group. This is the first study to comprehensively assess the auditory functions of patients with hepatic glycogen storage disease. Audiological findings determined a significantly increased prevalence of conductive/ mixed type hearing loss in the patient group which is a new finding in the literature. Further studies with extended patient numbers are required to enlighten the underlying pathophysiology.

Effects of familial Mediterranean fever on the middle ear

ObjectiveTo evaluate middle and inner ear function and hearing status of children with familial Mediterranean fever (FMF). MethodsWe assigned 56 patients with FMF to the study group and 52 healthy volunteers to the control group. The mean age of patients in the study and control groups were 10.10 ± 3.70 and 9.77 ± 3.74 years, respectively. Physical examination and hearing evaluation were performed in both groups. The audiological test battery included 226-Hz tympanometry, pure tone audiometric evaluation, acoustic stapedial reflex measurements, distortion product otoacoustic emission recording, and wide-band tympanometry assessment. ResultsThe groups were similar in age and sex ratio (p > 0.05 for both comparisons). Pure tone audiogram and distortion product otoacoustic emission results were also similar for both groups (p > 0.05). The ipsilateral acoustic stapedial reflex were present in both of the groups and all participants had Type A tympanogram. The contralateral acoustic stapedial reflex thresholds were significantly higher in the familial Mediterranean fever group (p < 0.05 for all comparisons). The ambient and peak pressure absorbance values of wide-band tympanometry were significantly lower at 2000 Hz and significantly higher at 4000 Hz in the familial Mediterranean fever group (p < 0.05 for both comparisons). The severity and duration of disease adversely affected the absorbance values of wide-band tympanometry at 2000 and 4000 Hz (p < 0.05). ConclusionTo our knowledge, this is the first study to demonstrate the adverse subclinical effects of familial Mediterranean fever on the middle ear. We recommend that children diagnosed with FMF should be closely monitored for future clinical middle ear pathologies.

Evaluation of hearing in patients with rheumatoid arthritis compared with controls

Objective: To demonstrate the effects of rheumatoid arthritis (RA) on hearing with audiometric and tympanometric measurements, and to reveal its relationship with the disease in comparison with healthy volunteers. Methods: The study included 30 RA patients and 30 healthy controls. Demographic findings such as age, height, weight, onset of complaint (year), time elapsed since diagnosis, previous surgery, accompanying systemic disease, drugs used, family history, habits of smoking and alcohol use were questioned for both groups. Tympanometry, pure voice audiometry and otoacoustic Emission tests were performed. Results: The hearing thresholds in the airway conduction in RA group were significantly higher in all frequencies (0.25-6 kHz) than in the control group. When bone conduction hearing thresholds were compared, RA group was more affected at only 4 kHz and left ear (p=0.006). When air-bone conduction differences (AB-gap) were examined, the differences in the RA group at 0.5, 1 and 4 kHz were statistically significant. When tympanometry and acoustic reflex measurement results were evaluated, there was no statistically significant difference between groups. In the transient OAE test, 3 (10 %) patients were in the RA and 2 (6.6 %) patients in the control group (p=0.064). Conclusion: Conductive hearing loss was significantly more frequent in patients with RA than in healthy individuals, whereas bone conduction was affected partially at high frequencies; whereas stapes reflex, compliance and pressure values were not significantly affected.

Age-related changes of otoacoustic emission

The aim of the study was to assess age-related changes of the transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) as well as to evaluate age-related changes of DPOAE suppression in adult subjects with normal hearing and presbycusis. Only women participated in the study: 26 young women with normal hearing (20-31 years old) were included into the first group; the second group consisted of 28 elderly (60-74 years old) with normal hearing; the third group included 28 elderly women with presbycusis (mild-to-moderate hearing loss). Age-related decrease of prevalence and amplitude of OAEs was proved to be significant; no significant differences of these data for left and right ears were revealed. Contralateral suppression of DPOAE was noted more often and was the greatest in young listeners and was presented in all frequency range, meanwhile the suppression was minimal and rarely noted in patients with presbycusis. The DPOAE amplitude enhancement in the contralateral noise condition was recorded in all groups of listeners, more often in aged patients both with normal hearing and hearing loss. These results may indicate age-related changes of medial olivocochlear complex, which take place not only in patients with hearing loss but in normal hearing subjects as well.. The findings were confirmed by the results of acoustic reflex measurements obtained in this study.

Longitudinal analysis of the audiological phenotype in osteogenesis imperfecta: a follow-up study.

This prospective study involved a longitudinal analysis of the progression of hearing thresholds in patients with osteogenesis imperfecta. Audiometric results from 36 osteogenesis imperfecta patients (age range, 6-79 years) were compared between two test times with an average interval of 4 years. Audiometric evaluation included acoustic admittance measurements, acoustic stapedial reflex measurements, pure tone audiometry and otoacoustic emissions testing. Air conduction pure tone average, corrected for sex and age, and bone conduction pure tone average increased significantly in the study population (p < 0.05 and p < 0.001, respectively). In 14.3 per cent of the evaluated ears, an alteration in type and/or severity of hearing loss was observed. After an average time interval of four years, significant changes in hearing status occurred in a population of osteogenesis imperfecta patients. These findings highlight the importance of regular audiological follow up in osteogenesis imperfecta patients, including audiometry, and measurements of acoustic admittance, acoustic stapedial reflexes and otoacoustic emissions.

Objective evaluation of binaural summation through acoustic reflex measures

Objective: A previous study [Rawool, V. W. (2016). Auditory processing deficits: Assessment and intervention. New York, NY: Thieme Medical Publishers, Inc., pp. 186–187] demonstrated objective assessment of binaural summation through right contralateral acoustic reflex thresholds (ARTs) in women. The current project examined if previous findings could be generalised to men and to the left ear. Design: Cross-sectional. Study sample: Sixty individuals participated in the study. Left and right contralateral ARTs were obtained in two conditions. In the alternated condition, the probe tone presentation was alternated with the presentation of the reflex activating clicks. In the simultaneous condition, the probe tone and the clicks were presented simultaneously. Binaural summation was calculated by subtracting the ARTs obtained in the simultaneous condition from the ARTs obtained in the alternated condition. Results: MANOVA on ARTs revealed no significant gender or ear effects. The ARTs were significantly lower/better in the simultaneous condition compared to the alternated condition. Conclusions: Binaural summation was 4 dB or higher in 88% of the ears and 6 dB or higher in 76% of ears. Stimulation of six out of the total 120 (0.5%) ears resulted in worse thresholds in the simultaneous condition compared with the alternating condition, suggesting binaural interference.

Acute Moderate Exercise Improves Working Memory Efficiency In Humans

BACKGROUND: Despite evidence indicating that a single bout of exercise can reduce state anxiety and improve cognitive function, (for review Chang et al. 2015, Ensari et al. 2015) few studies have examined the impact of acute exercise on the relationship between anxiety and cognition. The current study explores the modulatory effects of exercise on anxiety and working memory (WM) performance. Moderate exercise, compared to light exercise, was expected to improve WM performance, while decreasing self-reported anxiety and physiological measures (anxiety-potentiated startle) of anxiety. METHODS: Healthy adults (N = 21) of varied physical fitness levels underwent three exercise sessions on a cycle ergometer: one maximal exercise test to assess maximal heart rate (HR) and two subsequent randomized 30-minute exercise sessions at moderate (60-70% HR reserve (HRR)) and low (10-20% HRR) intensities. After exercise, subjects performed a WM task (n-back) under threat of unpredictable electric shock and safe conditions. Anxiety was probed using the acoustic startle reflex and retrospective subjective measures. WM performance (accuracy and reaction time), subjective anxiety, and startle variables were analyzed using 3-way ANOVAs, with Condition (threat, safety), Load (0-back, 1-back, 3-back), and Exercise (light, moderate) as within-subject factors. RESULTS: Participants reported higher subjective feelings of anxiety and had a greater startle response in the threat compared to the safe condition. Moderate intensity exercise resulted in a faster reaction time at a trend level time (F(1,19) = 3.34, p = 0.08) without compromising accuracy. This was most notable during the 3-back WM level (F(2,18) = 3.69, p = 0.05) during both safe and threat contexts. There was no effect of exercise level on subjective anxiety or anxiety-potentiated startle. CONCLUSION: Acute moderate exercise improves cognitive efficiency (shorter reaction times) without compromising accuracy but does not reduce elevated state anxiety. This might be due to an increase in arousal that affects reaction time but not the distribution of working memory resources between cognitive function and anxiety. If this pattern strengthens with the full sample (N=36), we will (1) move to a patient population, and (2) apply this protocol to a neuroimaging study.

Performance of children with mild or moderate sensory hearing loss on central auditory tests

Hearing is fundamental to the development of successful language skills. Deficits in hearing acuity and auditory processing (AP) can profoundly obstruct effective communication. Our study aimed to evaluate the performance of children with mild and moderate sensory hearing loss (HL) on central AP tests. The study included 50 children: 10 children with normal hearing who were used as controls; 20 children with mild sensory HL; and 20 children with moderate sensory HL. Both male and female children were equally represented. All children underwent otoscopic examination, pure tone audiometry, tympanometry, and acoustic reflex measurements. Questionnaires on central AP disorders, dyslexia, and attention deficit hyperactivity disorder were answered by the parents. Screening tests for AP abilities [pitch pattern sequence test, speech perception in noise (SPIN) right SPIN, left SPIN, dichotic digit test] were conducted. All children were then examined with the full versions of the previous tests in addition to auditory fusion test − revised, masking level difference test, binaural fusion test, competing sentence test, and low pass-filtered test. Arabic-version dyslexia assessment was carried out for those who failed the tests. The study revealed that children with mild and moderate HL who failed the screening tests also failed the full version tests, and when tested by the Arabic-version dyslexia assessment test, dyslexia was found as a comorbid condition.

Prevalence and Nature of Hearing Loss in 22q11.2 Deletion Syndrome.

The purpose of this study was to clarify the prevalence, type, severity, and age-dependency of hearing loss in 22q11.2 deletion syndrome. Extensive audiological measurements were conducted in 40 persons with proven 22q11.2 deletion (aged 6-36 years). Besides air and bone conduction thresholds in the frequency range between 0.125 and 8.000 kHz, high-frequency thresholds up to 16.000 kHz were determined and tympanometry, acoustic reflex (AR) measurement, and distortion product otoacoustic emission (DPOAE) testing were performed. Hearing loss was identified in 59% of the tested ears and was mainly conductive in nature. In addition, a high-frequency sensorineural hearing loss with down-sloping curve was found in the majority of patients. Aberrant tympanometric results were recorded in 39% of the ears. In 85% of ears with a Type A or C tympanometric peak, ARs were absent. A DPOAE response in at least 6 frequencies was present in only 23% of the ears with a hearing threshold ≤30 dB HL. In patients above 14 years of age, there was a significantly lower percentage of measurable DPOAEs. Hearing loss in 22q11.2 deletion syndrome is highly prevalent and both conductive and high-frequency sensorineural in nature. The age-dependent absence of DPOAEs in 22q11.2 deletion syndrome suggests cochlear damage underlying the high-frequency hearing loss.

Evaluation of Acoustic Reflex and Reflex Decay Tests in Geriatric Group.

To determine average acoustic reflex thresholds in geriatric groups by assessing ipsilateral and contralateral acoustic reflex and reflex decay tests. A total of 25 elders between ages 65-84 years (74.3±5.4) and 25 individuals between ages 18-45 years (30.4±4.2) were recruited for the study. After ear, nose, and throat examination, ipsilateral and contralateral acoustic reflex thresholds at 500, 1000, 2000, and 4000 Hertz (Hz) were determined and a reflex decay test at contralateral 500 Hz was conducted. Ipsilateral acoustic reflex thresholds were obtained with high-frequency band, low-frequency band, and wide band noise, and the results were compared with ipsilateral acoustic reflexes at 500, 1000, 2000, and 4000 Hz. There was no statistically significant difference between the two groups in ipsilateral and contralateral acoustic reflex measurements at 500, 1000, 2000, and 4000 Hz (p>0.05). Negative reflex decay was obtained in all participants and no statistically significant difference between the two groups was observed in terms of reflex decay thresholds (p>0.05). Acoustic reflex with high-frequency band noise was observed in five of nine elders whose acoustic reflexes were not obtained at 2000 and 4000 Hz, whereas acoustic reflex with low-frequency band noise was observed in one of six elders who did not show reflexes at 500 and 1000 Hz. It was concluded that although some changes were observed due to age, middle ear and stapes muscles work normally in geriatric group. In the reflex decay test, reliable results were obtained at contralateral 500 Hz. Acoustic reflex measurements with low- and high-frequency band noise may also be used to assess middle ear functions.

Evaluation of Prevalence and Factors Affecting the Development of Middle Ear Effusion in Patients with Prolonged Intubation in Intensive Care Unit

Objective: Monitorization of patients in intensive care units requires a multidisciplinary approach. As cooperation with unconscious or intubated patients is often not possible, some conditions may be overlooked. The aim of this study is to reveal the incidence and factors affecting otitis media with effusion in ICU patients intubated longer than 7 days. Methods: Twenty patients hospitalized in the intensive care unit of the Gaziosmanpasa Taksim Training and Research Hospital from March to December 2014 were included in the study. The Gaziosmanpasa Taksim Training and Research Hospital Ethics Committee approved the study according to the Declaration of Helsinki and Good Clinical Practices guidelines. All of the patients included in the study were aged ≥18 years. Patients intubated because of traffic accidents or trauma, patients with a history of chronic otitis media or ear, nose, and throat operations, patients with head and neck tumors, and patients with tympanic membrane perforation, external auditory canal pathology, nasopharyngeal mass, and chronic sinusitis as well as patients with a pathology leading to nasal obstruction, such as nasal polyposis or severe septal deviation, were excluded. After a detailed history by patients’ relatives, an otoscopic examination, nasal examination, tympanometry, and acoustic reflex measurements were performed. Ear examination was performed using a conventional portable otoscope. Results: Among 20 patients, 12 had bilateral effusion (24 out of 40 ears, 60%). In two patients, a type C tympanogram was obtained (four out of 40 ears, 10%), and the remaining 12 ears of six patients were normal (30%). When intubation time is evaluated, among 13 patients intubated longer than 14 days, 11 had effusion (84%). A significant correlation was found between the duration of intubation and effusion development. Assessing the state of consciousness, 11 of 12 unconscious patients (91%) were found to have effusion. There was a significant correlation between effusion development and state of consciousness. Conclusion: In unconscious patients intubated longer than 14 days, the risk of having middle ear effusion is demonstrated to be higher. Consequently, in the periodic follow-up of intensive care patients with prolonged intubation, a routine otoscopic examination has to be considered. (JAREM 2015; 5: 64-7)

Middle ear muscle reflex measurement in neonates: Comparison between 1000 Hz and 226 Hz probe tones

IntroductionMiddle ear muscle reflex (MEMR) evaluation assists in diagnosing hearing problems because normal responses depend on preconditions of a healthy auditory system. Studies in neonates recording the acoustic reflex with 226Hz probes have described high rates of absence. Other studies using a high frequency probe have found higher rates of presence in normal neonates. However, few studies have compared results between low and high frequency probes in the same newborns. ObjectiveTo comparatively assess the ipsilateral acoustic reflex recorded by 226Hz and 1000Hz probes in newborns. MethodA total of 77 newborns, with the presence of transient otoacoustic emissions, underwent tympanometry, wideband acoustic immittance, and ipsilateral reflex investigations with 226Hz and 1000Hz tone probes. ResultsThe acoustic reflex was activated at a much lower intensity with all activating stimuli using the 1000Hz probe compared with the values of the 226Hz probe. There was a higher incidence of ipsilateral acoustic reflexes recorded by the 1000Hz tone probe compared to the 226Hz tone probe. There was no correlation between the acoustic reflex thresholds and otoacoustic emissions. ConclusionIn newborns, the acoustic reflex measurements obtained with the 1000Hz probe showed advantages over the 226Hz probe.

Acoustic startle reflex and pre-pulse inhibition in tinnitus patients

Gap induced pre-pulse inhibition (Gap-PPI) of acoustic startle reflex has been used as a measurement of tinnitus in animal models. However, whether this test is sensitive to detect tinnitus in humans is still unclear. Based on the testing procedure used in animal studies, a human subject testing method was formulated and conducted to investigate if a similar result could be found in tinnitus patients. Audiologic and tinnitus assessments and acoustic startle reflex measurements were performed on seven tinnitus subjects and nine age matched subjects without tinnitus. There was no significant difference found between the control and tinnitus group on the Gap-PPI across the frequencies evaluated. The amplitude of the startle response in the tinnitus group with normal hearing thresholds was significantly higher than the control group and those with tinnitus and hearing loss. This preliminary result suggests that hyperexcitability in the central auditory system may be involved in tinnitus. There was no correlation between hearing thresholds and the increased amplitude of startle response.

Fast psychophysical tuning curves of the cochlea in normal hearing individuals

Introduction Fast psychophysical tuning curve (fPTC) test is a fast computer-based method that aims to assess the frequency selectivity of the cochlea and to detect the dead regions. It can quickly identify tip frequency and Q10 of psychophysical tuning curves (PTCs) derived by using a band of noise that changes in center frequency and a Bιkιsy method to adjust the masker level required for threshold of the noise. We applied this method in normal hearing individuals in the presence of threshold equalizing noises at three signal levels. The sharpness of the PTCs (Q10) and the typical shift of tips of the PTCs for 16 normal hearing individuals, when the tip frequency is estimated for the average of a forward and reverse sweep, were obtained. The results were used to determine the mean, SD, and 95% confidence interval of the shifts in normal hearing individuals. Objective The purpose of this experiment was to estimate the typical shift of tips of the PTCs for normal hearing individuals. The results were used to determine the mean, SD, and 95% confidence interval of the shifts. The sharpness of the PTCs change with signal level under conditions where off-frequency listening is restricted, using a background noise, was also assessed. This was performed to allow a comparison with the results of hearing-impaired patients tested at the same level (but without background noise). Study design Sixteen adults of both sexes (eight male individuals and eight female individuals) were randomly selected to establish normative data for the fPTC test. They were selected with age ranging from 18 to 45 years. All individuals had normal middle ear function as indicated by tympanometry and acoustic reflex measurement and by hearing threshold equal to or better than 20 dB at octave frequencies in the frequency range (250-8000 Hz) (as defined by ANSI S3.6-2004).

Distortion product otoacoustic emission fine-structure: An insight into the ear asymmetries

Context: Use of distortion product otoacoustic emission (DPOAE) as a measure of hearing sensitivity is common in clinical practice. However, use of a more informative DPOAE fine-structure has been limited due to non-reliability of DPOAE fine-structure. Aim: The current study was aimed at testing the interaural differences between the DPOAE fine-structure across three age groups. Settings and Design: Acoustically treated room with a calibrated dual channel audiometer (Orbiter 922) along with TDH-39 headphones and B-71 bone vibrator. GSI Tympstar was used for tympanometry and acoustic reflex measurements while 'ILO V6' OAE analyzer was used for recording of DPOAE and DPOAE fine-structure. Material and Methods : A total of 98 subjects with normal peripheral hearing sensitivity were tested for DPOAE fine-structure. The three age groups consisted of young (8-18 years; n = 50), middle aged (30-40 years; n = 30), and elderly (50-60 years; n = 18). DPOAE fine-structure was studied at 8 points per octave on a total of 25 frequencies from 1000 to 8000 Hz. Statistical Analysis Used: Repeated measure analysis of variance. Results: There was a significant difference (P < 0.05) in the amplitudes at frequencies between 2000 and 3000 Hz. This was evident irrespective of the age groups. There was also a decrease in DPOAE amplitude in elderly group. Conclusions: Interaural asymmetry can be attributed as a reason to these findings and it occurred mostly in the speech perception frequencies. Reduced amplitude of DPAOE in the elderly group can be attributed to presbycusis.

Audiologic Phenotype of Osteogenesis Imperfecta

To describe the audiologic phenotype in osteogenesis imperfecta (OI). Observational study. Tertiary referral center. One hundred eighty-two patients with genetically confirmed OI, aged 3 to 89 years. Diagnostic hearing evaluation through otoadmittance and acoustic stapedius reflex measurements, pure tone, and speech audiometry. Prevalence, type, severity, symmetry, and audiometric configuration of the hearing loss in OI. Progression of hearing thresholds was determined by constructing age-related typical audiograms. Approximately 52.2% of all OI patients demonstrated hearing loss unilaterally (7.7%) or bilaterally (44.5%). Pure conductive, mixed, and pure sensorineural hearing losses were observed in 8.5%, 37.8%, and 11.6% of OI ears, respectively. Multiple linear regression revealed that thresholds progressed by 0.5 dB/yr at 0.25 kHz to 0.8 dB/yr at 0.8 kHz in the ears with conductive or mixed hearing loss. Pure sensorineural hearing loss progressed by less than 0.1 dB/yr at 0.25 kHz to 1.2 dB/yr at 8.0 kHz. Audiometric configuration was predominantly flat (70.5%) in the ears with conductive/mixed loss and sloping (50.0%) in those with pure sensorineural loss. Patients with OI are at risk for hearing loss. The hearing loss in OI may initiate at a young age and is progressive. However, the rate of progression, as well as the hearing loss severity, onset, and configuration depend on the type of hearing loss, which may be conductive/mixed or pure sensorineural. For both types, age-related threshold audiograms are constructed and may help the clinician to estimate the course of the hearing loss in patients with OI. In addition, they may be valuable to distinguish between hearing loss associated with OI and other similar forms of hearing loss, such as in otosclerosis.

Acoustic Stapedial Reflex Test Modification in Ears with High Static Admittance and Asymmetric Hearing Loss: A Case Study

AbstractPatients with high peak compensated static acoustic admittance (Ytm) tympanograms often have normal-appearing audiometric presentations. However, this tympanometric condition may render acoustic stapedial reflex (ASR) thresholds immeasurable because of fluctuating ear canal pressure and responselike artifacts obtained irrespective of the stimulus level. There is a paucity of information in the literature about this responselike artifact and a potential technical modification to manage it. Here we describe for the first time the use of the ASR test modification with a case of bilateral high peak Ytm tympanograms and audiometrically determined uniunilateral sensorineural hearing loss in the left ear with concerns about retrocochlear pathology. Standard audiologic procedures were completed along with a modified ASR test, and distortion-product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing. Fluctuating ear canal pressure prevented reliable acoustic reflex measurements. Aft...

Assessment of auditory brainstem function in lead-exposed children using stapedius muscle reflexes

The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125–4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2–18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n = 117) ranged from 4.0 to 83.7 μg/dL with a mean PbB level of 33.5 μg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n = 91) of the children had PbB levels greater than the CDC action line of 10 μg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤ 90 dB HL) and contralateral (mean: ≤ 97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of stapedius muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.

Auditory Brainstem Responses in Patients under Treatment of Hemodialysis

This study evaluated the effects of end stage chronic renal failure (CRF) on auditory function and changes in auditory function following a single session of hemodialysis. The experimental group included 31 patients with end-stage renal failure on chronic hemodialysis. The control group consisted of 31 healthy volunteers. The patients were examined prior to and following a session of hemodialysis. Measurements included pure tone audiometry, tympanometry and acoustic reflex measurements, auditory brainstem responses (ABR), and blood now chemistry parameters. Controls underwent the same test battery, with the exception of biochemical and hematological assessment. Prior to hemodialysis sessions, all ABR latencies except interpeak latency I–III were significantly prolonged in the experimental group. A comparison between controls and the experimental group following hemodialysis indicated that wave V absolute latency and interpeak latencies III–V and I–V were significantly prolonged in the slow repetition rate paradigm. In the fast repetition rate, absolute latencies of waves I and V and III–V interpeak latencies were prolonged in the experimental group. Comparison of ABR recordings prior to and following hemodialysis showed overall significant difference between the measures. Post hoc analysis showed a significant improvement in wave I and V latencies in the slow repetition rate and wave V latency in the fast repetition rate. This study showed that neural conduction along the auditory pathway is delayed in patients with end stage CRF as compared to healthy subjects. Dialysis sessions improve overall neural auditory function. However, patients with end stage CRF show delayed conduction even after a session of hemodialysis.