Auditory Middle Latency Responses Research Articles

Phenotypic spectrum of tinnitus patients bearing rare ANK2 gene variants.

To describe the clinical, audiological, and psychometric features observed in patients with chronic tinnitus and rare variants in the ANK2 gene. We report a case series of 12 patients with chronic tinnitus and heterozygous variants in the ANK2 gene. Tinnitus phenotyping included audiological (standard and high-frequency audiometry, Auditory Brainstem Responses (ABR) and Auditory Middle Latency Responses (AMLR)), psychoacoustic and psychometric assessment by a Visual Analog Scale (VAS) for tinnitus annoyance, the Tinnitus Handicap Inventory (THI), the test on Hypersensitivity to Sound (THS-GÜF), the Patient Health Questionnaire (PHQ-9), the Hospital Anxiety and Depression Scale (HADS) and the Montreal Cognitive Assessment (MoCA). All patients reported a persistent, unilateral noise-type tinnitus, mainly described as white noise or narrowband noise. Seven patients (58%) were considered to have extreme phenotype (THI score > 76), and all patients reported some degree of hyperacusis (THS-GÜF score > 18 in 75% of patients). Seven patients scored MoCA < 26, regardless of the age reported, suggesting a mild cognitive disorder. ABR showed no significant differences in latencies and amplitudes between ears with or without tinnitus. Similarly, the latencies of Pa, Pb waves, and NaPa complex in the AMLR did not differ based on the presence of tinnitus. However, there were statistical differences in the amplitudes of Pa waves in AMLR, with significantly greater amplitudes observed in ears with tinnitus. Patients with ANK2 variants and severe tinnitus exhibit an endophenotype featuring hyperacusis, persistent noise-like tinnitus, high-frequency hearing loss, and decreased amplitudes in AMLR. However, anxiety, depression, and cognitive symptoms vary among individuals.

My Perspective: Auditory Evoked Potentials Using Speech

Purpose: The purpose of this tutorial is to clarify the use of speech sounds as stimuli for auditory evoked potentials and how these might contribute to our understanding of speech, language, learning, and hearing disorders. Speech-evoked auditory brainstem responses (ABRs), auditory steady-state responses, auditory middle latency responses, mismatch negativity, P300, cortical onset responses, and the acoustic change complex are reviewed. Method: The author drew upon her scholarship in this area from over 4 decades of research and teaching to summarize the major findings when using speech stimuli to evoke auditory potentials that have been used in clinical contexts. Results: Speech-evoked auditory potentials contribute to our understanding of how the brain processes the acoustic features of speech sounds, providing information that is complementary to psychophysical tests. When psychophysical tests cannot be performed owing to neurodevelopmental immaturity or disability, or cognitive disability, speech-evoked auditory potentials may be used to estimate the benefit of amplification or implantation for speech, language, and hearing. Conclusions: The benefit of using auditory evoked potentials for evaluation is that they provide insight into the brain mechanisms underlying hearing and listening disorders that audiologists aim to treat. While we can use the known correlations between perceptual and electrophysiological responses for “cross-checking” our evaluation results, examining when discrepancies occur is also especially meaningful. For example, the complex ABR reveals subcortical issues in temporal processing that would not be evident in ABRs to clicks or tone bursts, nor in behavioral testing. P300 can document slower neural processing of speech stimuli that may be relevant to the rehabilitation of older adults, even when word recognition scores appear to be congruent with the pure-tone audiogram. In these ways, auditory evoked potentials for speech provide audiologists with tools for demonstrating to clients how their brain responds to speech and opening the conversation for rehabilitation.

Habituation disorders in auditory middle latency response of persistent postural-perceptual dizziness patients.

To study habituation disorders in auditory middle latency response (AMLR) to repetitive stimuli of persistent postural-perceptual dizziness (PPPD) patients. Twenty-eight PPPD (10 men and 18 women, mean 59.5 years of age, 26-81 years of age) were enrolled. For comparison, data of 13 definite vestibular migraine (VM) patients (3 men, 10 women, mean age 45.5), 13 definite unilateral Meniere's disease (MD) patients (2 men, 11 women, mean age 50.6), and 8 healthy control (HC) subjects (2 men, 6 women, mean age 37.1) in the previous study were utilized. The electrodes were placed on the vertex and the spinal process of the fifth cervical vertebra. Clicks (0.1 msec, 70 dB nHL) were binaurally presented and averaged (800 times). Averaged responses were divided into 4 sets (S1 to S4) according to the temporal order. As peaks, Na, and Pa were identified, and relative Na-Pa amplitudes in S2-S4 to S1 were analyzed. The mean relative amplitude of PPPD patients showed lack of habituation (potentiation) as shown in VM patients, although the extent of potentiation was weaker than VM. Comparison of relative S4 amplitudes showed significant differences among the 4 groups (p = 0.0013 one-way ANOVA), Multiple comparison revealed significant differences between PPPD and MD (p = 0.0337 Dunnet's test). PPPD patients showed lack of habituation (potentiation) of Na-Pa amplitude in AMLR to repetitive stimuli. Lack of habituation (potentiation) might be associated with sensory processing disorders in PPPD.

Development of Machine-Learning Models for Tinnitus-Related Distress Classification Using Wavelet-Transformed Auditory Evoked Potential Signals and Clinical Data.

Tinnitus is a highly prevalent condition, affecting more than 1 in 7 adults in the EU and causing negative effects on sufferers' quality of life. In this study, we utilised data collected within the "UNITI" project, the largest EU tinnitus-related research programme. Initially, we extracted characteristics from both auditory brainstem response (ABR) and auditory middle latency response (AMLR) signals, which were derived from tinnitus patients. We then combined these features with the patients' clinical data, and integrated them to build machine learning models for the classification of individuals and their ears according to their level of tinnitus-related distress. Several models were developed and tested on different datasets to determine the most relevant features and achieve high performances. Specifically, seven widely used classifiers were utilised on all generated datasets: random forest (RF), linear, radial, and polynomial support vector machines (SVM), naive bayes (NB), neural networks (NN), and linear discriminant analysis (LDA). Results showed that features extracted from the wavelet-scattering transformed AMLR signals were the most informative data. In combination with the 15 LASSO-selected clinical features, the SVM classifier achieved optimal performance with an AUC value, sensitivity, and specificity of 92.53%, 84.84%, and 83.04%, respectively, indicating high discrimination performance between the two groups.

Diagnosis of Patients Presenting with Vertigo, Headache, and Epileptic Seizure: Evaluating Vestibular Patients by Using Cervical Vestibular Evoked Myogenic Potential and Auditory Middle Latency Responses in the Clinical Setting.

Migraine and vertigo are common complaints seen in clinical practice, and in a few such cases, we also find epileptic manifestations, including migraine-triggered seizures. Currently, patients presenting with vertigo and headache are diagnosed according to established diagnostic criteria for Meniere's disease, vestibular migraine, or vestibular migraine/Meniere's disease overlapping syndrome. In addition to using those diagnostic criteria and the patient's history, cervical vestibular evoked myogenic potential and auditory middle latency responses are useful tools to better understand the physiological background of these patients and also to confirm the diagnosis. Here we report 2 cases: 1 of vestibular migraine/ Meniere's disease overlapping syndrome and 1 of vestibular migraine with epileptic manifestations. Each patient showed potentiation (lack of habituation) in auditory middle latency response, and each showed endolymphatic hydrops in cervical vestibular evoked myogenic potential. The potentiation in auditory middle latency response might be attributable to neuronal hyperexcitability in those patients with migraine or epilepsy, and neurogenic inflammation caused by migraine episodes might affect inner ear function.

Study of aged central auditory function using the auditory middle latency response

ObjectiveInvestigate the auditory function of the elderly using the middle latency potentials. MethodologyGroup 1 (G1): 20 healthy individuals of both genders, older than 60 years, without hearing loss. Group 2 (G2): 20 healthy individuals of both sexes, older than 60 years, with hearing loss in frequencies from 4 to 8 kHz. Potential recording was performed with unilateral and bilateral stimulation and the Binaural Interaction Component was calculated. ResultsNa latency in C3A1 was greater in the stimulation of the right ear in G2 and the amplitude of Na-Pa was greater in the stimulation of the right ear and recording in C3A1 in G1. The latency of the Pa component was higher in the stimulation of the right ear recorded in C4A2. The Pb component in G2 by bilateral stimulation and recorded in C4A2 had higher latency. The first and second negative and positive peaks presented greater amplitude in G1. In C3A1, the 1st negative peak was more negative in G1 and the 2nd positive peak showed greater amplitude in C4A2 in both groups. ConclusionThe transmission of auditory information to the primary auditory cortex is impaired with aging, especially in unilateral stimulation, reinforced by losses in elderly people with peripheral hearing loss, such as in the binaural interaction at the cortical and subcortical levels. Thus, the AMLR has shown to be a sensitive examination to investigate neuroauditory disorders in the elderly, especially related to high-frequency hearing loss and primary auditory cortex dysfunctions caused by the aging process.

Auditory middle latency responses and hearing skills in adults

RESUMO Objetivo: comparar a latência e a amplitude dos componentes Na, Pa, Nb e Pb do Potencial Evocado Auditivo de Média Latência em adultos com e sem alterações em habilidades auditivas, bem como analisar a sensibilidade e a especificidade dos valores de corte de 30% e 50% para o Efeito de Orelha. Métodos: compuseram a amostra 32 indivíduos de ambos os sexos e sem perda auditiva, sendo subdivididos em Grupo 1 (16 indivíduos sem alterações em habilidades auditivas) e Grupo 2 (16 indivíduos com alterações em habilidades auditivas). Todos os participantes foram submetidos a uma avaliação audiológica e aos Potenciais Evocados Auditivos de Tronco Encefálico de Média Latência. O teste ANOVA foi utilizado na análise dos dados, considerando significantes os valores de p menores ou iguais a 0,05. Resultados: foi observada diferença estatisticamente significante apenas na amplitude de Na e Pa, quando Grupo 1 e Grupo 2 foram comparados. Esta diferença foi observada nas ondas A1C3 e A2C3. Na análise de sensibilidade e especificidade do Potencial Evocado Auditivo de Média Latência, observou-se que o valor de corte de 50% apresentou um melhor equilíbrio entre os critérios de sensibilidade e especificidade. Conclusão: os indivíduos adultos com alterações nas habilidades auditivas apresentaram menor amplitude de resposta nos componentes Na e Pa das ondas geradas no hemisfério esquerdo. O valor de corte de 50% apresentou um melhor equilíbrio na análise do Efeito de Orelha para a contribuição no diagnóstico de alterações de habilidades auditivas.

Potencial evocado auditivo de média latência e habilidades auditivas em adultos

ABSTRACT Purpose: to compare the Auditory Middle Latency Response in adults, one group with and another group without altered auditory skills. In addition, the aim was to compare cut-off values of 30% and 50% for the Ear Effect in terms of sensitivity and specificity. Methods: the sample comprised 32 individuals of both genders with no hearing loss who were divided into Group 1 (16 individuals with no alterations in auditory skills) and Group 2 (16 individuals with alterations in auditory skills). All participants received an audiological evaluation and measurement of Brainstem and Auditory Middle Latency Potentials. Results: when Group 1 and Group 2 were compared, a statistically significant difference was only observed in Na and Pa amplitude of waves A1C3 and A2C3. In the analysis of sensitivity and specificity of the Auditory Middle Latency Response, a cut-off value of 50% gave a better balance between sensitivity and specificity. Conclusion: adults presented with altered auditory abilities had smaller response amplitudes in the Na and Pa components of the waves generated in the left hemisphere. A cut-off value of 50% gave a better discrimination of the Ear Effect for identifying subjects with altered auditory skills.

Development and Evaluation of Automated Tools for Auditory-Brainstem and Middle-Auditory Evoked Potentials Waves Detection and Annotation.

Auditory evoked potentials (AEPs) are brain-derived electrical signals, following an auditory stimulus, utilised to examine any obstructions along the brain neural-pathways and to diagnose hearing impairment. The clinical evaluation of AEPs is based on the measurements of the latencies and amplitudes of waves of interest; hence, their identification is a prerequisite for AEP analysis. This process has proven to be complex, as it requires relevant clinical experience, and the existing software for this purpose has little practical use. The aim of this study was the development of two automated annotation tools for ABR (auditory brainstem response)- and AMLR (auditory middle latency response)-tests. After the acquisition of 1046 raw waveforms, appropriate pre-processing and implementation of a four-stage development process were performed, to define the appropriate logical conditions and steps for each algorithm. The tools' detection and annotation results, regarding the waves of interest, were then compared to the clinicians' manual annotation, achieving match rates of at least 93.86%, 98.51%, and 91.51% respectively, for the three ABR-waves of interest, and 93.21%, 92.25%, 83.35%, and 79.27%, respectively, for the four AMLR-waves. The application of such tools in AEP analysis is expected to assist towards an easier interpretation of these signals.

Frequency-Following Response e Potencial Evocado Auditivo de Média Latência: uma análise frente ao processamento auditivo central de jovens adultos

ABSTRACT Purpose: to compare the latency and amplitude of the Frequency-Following Response and the Auditory Middle Latency Response in typical individuals and those with altered auditory abilities, as well as to investigate the sensitivity and specificity of both assessments in relation to central auditory processing. Methods: 32 individuals of both sexes were distributed into Group 1 (without altered auditory abilities) and Group 2 (with altered auditory abilities). The groups were divided according to behavioral tests of central auditory processing. Individuals in both groups underwent auditory evoked potentials. Student’s t-test was used for analysis, considering a 5% significance. Results: in Group 2, V and A had higher latency and lower amplitude and slope. Group 2 also had lower Na and Pa amplitudes in waves A1C3 and A2C3. The Frequency-Following Response showed 93% sensitivity and specificity, while the Auditory Middle Latency Response showed 87% sensitivity and 93% specificity. Conclusion: the individuals presented with altered hearing abilities showed higher latency and lower response amplitude in the Frequency Following Response and Auditory Middle Latency Response compared to typical individuals. The Frequency- Following Response showed a better balance of sensitivity and specificity.

Frequency-Following Response and Auditory Middle Latency Response: an analysis of central auditory processing in young adults

RESUMO Objetivo: comparar a latência e a amplitude do Frequency-Following Response e do Potencial Evocado Auditivo de Média Latência em indivíduos típicos e com alterações das habilidades auditivas, assim como investigar a sensibilidade e especificidade de ambas as avaliações frente ao processamento auditivo central. Métodos: 32 indivíduos de ambos os sexos foram distribuídos em Grupo 1 (sem alterações de habilidades auditivas) e Grupo 2 (com alteração em habilidades auditivas). Os grupos foram divididos de acordo com testes comportamentais do processamento auditivo central. Os indivíduos de ambos os grupos foram submetidos aos potenciais evocados auditivos. O teste T de Student foi utilizado para a análise, considerando 5% de significância. Resultados: no Grupo 2, V e A apresentaram maior latência e menor amplitude e slope. O Grupo 2 também apresentou menores amplitudes de Na e Pa nas ondas A1C3 e A2C3. O Frequency-Following Response apresentou 93% de sensibilidade e especificidade, enquanto o Potencial Evocado Auditivo de Média Latência apresentou 87% de sensibilidade e 93% de especificidade. Conclusão: os indivíduos com alteração das habilidades auditivas apresentaram maior latência e menor amplitude de resposta no Frequency Following Response e Potencial Evocado Auditivo de Média Latência em relação aos indivíduos típicos. O Frequency-Following Response apresentou melhor equilíbrio de sensibilidade e especificidade.

Auditory Middle Latency Response in Young Adult Females Perceiving Tinnitus During a Brief Period of Silence

Auditory Middle Latency Response in Young Adult Females Perceiving Tinnitus During a Brief Period of Silence

Auditory evoked potentials: Differences by sex, race, and menstrual cycle and correlations with common psychoacoustical tasks.

Auditory brainstem responses (ABRs) and auditory middle-latency responses (AMLRs) to a click stimulus were measured in about 100 subjects. Of interest were the sex differences in those auditory evoked potentials (AEPs), the correlations between the various AEP measures, and the correlations between the AEP measures and measures of otoacoustic emissions (OAEs) and behavioral performance also measured on the same subjects. Also of interest was how the menstrual cycle affected the various AEP measures. Most ABR measures and several AMLR measures exhibited sex differences, and many of the former were substantial. The sex differences tended to be larger for latency than for amplitude of the waves, and they tended to be larger for a weak click stimulus than for a strong click. The largest sex difference was for Wave-V latency (effect size ~1.2). When subjects were dichotomized into Non-Whites and Whites, the race differences in AEPs were small within sex. However, sex and race interacted so that the sex differences often were larger for the White subjects than for the Non-White subjects, particularly for the latency measures. Contrary to the literature, no AEP measures differed markedly across the menstrual cycle. Correlations between various AEP measures, and between AEP and OAE measures, were small and showed no consistent patterns across sex or race categories. Performance on seven common psychoacoustical tasks was only weakly correlated with individual AEP measures (just as was true for the OAEs also measured on these subjects). AMLR Wave Pa unexpectedly did not show the decrease in latency and increase in amplitude typically observed for AEPs when click level was varied from 40 to 70 dB nHL (normal Hearing Level). For the majority of the measures, the variability of the distribution of scores was greater for the males than for the females.

Visual load does not decrease the auditory steady-state response to 40-Hz amplitude-modulated tones.

The auditory pathway consists of multiple recurrent loops of afferent and efferent connections that extend from the cochlea up to the prefrontal cortex. The early‐filter theory proposes that these loops allow top‐down filtering of early and middle latency auditory responses. Furthermore, the adaptive filtering model suggests that the filtering of irrelevant auditory stimuli should start lower in the pathway during more demanding tasks. If so, the 40‐Hz auditory steady‐state responses (ASSRs) to irrelevant sounds should be affected by top‐down crossmodal attention to a visual task, and effects should vary with the load of the visual task. Because few studies have examined this possibility, we conducted two preregistered studies that manipulated visual load (Study 1: N = 43, Study 2: N = 45). Study 1 used two levels (low and high), and Study 2 used four levels (no, low, high, and very high). Subjects were asked to ignore a 500‐Hz task‐irrelevant tone that was amplitude‐modulated to evoke 40‐Hz ASSRs. Results from Bayesian analyses provided moderate to extreme support for no effect of load (or of a task) on ASSRs. Results also supported no interaction with time (i.e., over blocks, over minutes, or with changes in ASSRs that were synchronized with the onset of the visual stimuli). Further, results provided moderate support for no correlation between the effects of load and working memory capacity. Because the present findings support the robustness of ASSRs against manipulations of crossmodal attention, they are not consistent with the adaptive filtering model.

Evidence of central involvement in essential tremor: a detailed study of auditory pathway physiology.

Essential tremor (ET) is a common tremor disorder that is likely neurodegenerative. The pathophysiology of ET involves the cerebellum and its connections in the brainstem and thalamus. Hearing dysfunction has been shown to be a non-motor finding in ET patients. A limited number of studies have suggested that cochlear pathology is the cause, but studies have not evaluated the integrity of the primary auditory pathway in ET. The main aim of this study is to investigate the integrity of the auditory pathway via auditory brainstem response (ABR) and auditory middle latency response (AMLR), thereby allowing us to evaluate the auditory pathway from the 8th cranial nerve to the cerebral cortex. Sixteen ET patients and sixteen age- and gender-matched controls (64 ears) were evaluated. In the ABR study, we detected prolongation of wave V peak latencies (ms) in ET (p = 0.02). In the AMLR study, P0 (p = 0.03), Pa (p = 0.008), Na (p = 0.03), and Nb (p = 0.01) waves differed between the two groups. Eleven ET patients and four control subjects had abnormal electrophysiological findings (ABR or AMLR or both) (68.8% vs. 25%, p = 0.01). Tremor duration was greater in ET patients with abnormal electrophysiological findings (p = 0.01). Finally, we observed prolongation of latencies after the ABR III wave, indicating that abnormalities exist within the superior olivary complex. For the first time, our research provides evidence that ET-related pathology is present at the subcortical and cortical levels of the auditory pathway.

Vestibular Migraine Patients Show Lack of Habituation in Auditory Middle Latency Responses to Repetitive Stimuli: Comparison With Meniere's Disease Patients

Objectives: To compare habituation in auditory middle latency response (AMLR) to repetitive stimuli of vestibular migraine (VM) patients with Meniere's disease (MD) patients and healthy controls (HC) and to assess usefulness of AMLR for diagnosis of VM.Subjects: Thirteen unilateral definite MD patients (2 men, 11 women, mean age 50.6), 13 definite VM patients (3 men, 10 women, mean age 45.5), and 8 HC subjects (2 men, 6 women, mean age 37.1) were enrolled.Methods: The electrodes were placed on the vertex and the spinal process of the fifth cervical vertebra. Binaural click stimulation (0.1 ms, 70 dBnHL) was presented. A total of 800 responses were averaged. Averaged responses were divided into four sets (S1 to S4) according to the temporal order. No, Po, Na, and Pa were identified, and amplitudes and latencies were measured.Results: Concerning latencies, HC subjects showed a tendency of shorter latencies. However, there was no clear effect of repetitive stimulation. Concerning No-Po amplitudes, no significant differences were observed. Raw amplitudes of Na-Pa showed statistically significant differences in S1 and S2 among the groups (p < 0.01 one-way ANOVA). Differences were shown in MD vs. VM and HC vs. VM in S1 (smaller in VM) (p < 0.01 Bonferroni's test) and in MD vs. VM in S2 (smaller in VM) (p < 0.01 Bonferroni test). Relative amplitudes of Na-Pa to S1 showed statistically significant differences in S4 (p < 0.01 one-way ANOVA). Differences were shown in MD vs. VM and HC vs. VM (larger in VM) (p < 0.01 Bonferroni's test). Differences of Na-Pa amplitudes in S2 to S4 from Na-Pa amplitude in S1 were significant in S4 of VM patients (Dunnett's test).Conclusions: VM patients showed lack of habituation (potentiation) of Na-Pa amplitude in AMLR to repetitive stimuli while MD patients and HC subjects showed habituation. Observation of lack of habituation has high diagnostic accuracy for differential diagnosis of VM from MD.

Effect of Music Training on Auditory Brainstem and Middle Latency Responses

Purpose: The auditory system has potentials to reorganize its structure and function in response to environmental changes such as training, experience, learning, injury, and disease. This is called neuroplasticity. A typical example of neuroplasticity is the music training, which demands cognitive and neural challenges resulting in enhanced auditory perception. This study investigated the effect of music training on auditory evoked responses, particularly auditory brainstem and middle latency responses. Methods: Forty college students consisting of twenty students with music training (musicians) and twenty students without music training (non-musicians) participated in the study. All participants have normal ranges in terms of pure tone audiometry, speech audiometry, and tympanometry. Auditory brainstem response (ABR) and auditory middle latency response (AMLR) from both ears were tested. Absolute latencies and amplitudes of waves in ABR and AMLR were obtained and analyzed.Results: The absolute latencies of wave I and V significantly differed between musicians and non-musicians. They were shorter for musicians than for non-musicians. Significant differences were found in the interpeak latencies of wave III-V and I-V between musicians and non-musicians. They were also shorter in musicians than for non-musicians. In addition, there were only significant differences in the latency of Na in AMLR between musicians and non-musicians. It was shorter for a musician than for non-musician.Conclusion: ABR was more sensitive to the efficacy of the music training.

Electrophysiological characteristics in children with listening difficulties, with or without auditory processing disorder

Objective: To determine if the auditory middle latency responses (AMLR), auditory late latency response (ALLR) and auditory P300 were sensitive to auditory processing disorder (APD) and listening difficulties in children, and further to elucidate mechanisms regarding level of neurobiological problems in the central auditory nervous system. Design: Three-group, repeated measure design.Study sample: Forty-six children aged 8–14 years were divided into three groups: children with reported listening difficulties fulfilling APD diagnostic criteria, children with reported listening difficulties not fulfilling APD diagnostic criteria and normally hearing children.Results: AMLR Na latency and P300 latency and amplitude were sensitive to listening difficulties. No other auditory evoked potential (AEP) measures were sensitive to listening difficulties, and no AEP measures were sensitive to APD only. Moderate correlations were observed between P300 latency and amplitude and the behavioural AP measures of competing words, frequency patterns, duration patterns and dichotic digits.Conclusions: Impaired thalamo-cortical (bottom up) and neurocognitive function (top-down) may contribute to difficulties discriminating speech and non-speech sounds. Cognitive processes involved in conscious recognition, attention and discrimination of the acoustic characteristics of the stimuli could contribute to listening difficulties in general, and to APD in particular.

Reference ranges and stability of auditory and vestibular measures in a comprehensive assessment battery for traumatic brain injury

Audiology clinics have many tools available to evaluate auditory and vestibular complaints. However, many tools lack established normative ranges across the life span. We conducted this study to establish reference ranges across the life span for audiology/vestibular measures commonly used to evaluate patients with traumatic brain injury. In this repeated measures study, 75 adults, ages 18-65 years, without a history of traumatic brain injury, underwent robust auditory/vestibular evaluations three times over six months, including rotational chair, videonystagmography, computerized dynamic posturography, vestibular evoked myogenic potentials, and retinal fundoscopy. Age effect was notable for transient evoked otoacoustic emissions, pure-tone audiometry, auditory brainstem response, auditory middle latency response, and auditory-steady state response at 4000 hertz (Hz). Older participants (50-65 years) were more likely to have delayed latency horizontal saccades, positional nystagmus, slowed lower-extremity motor control responses, and delayed latency ocular vestibular evoked myogenic potentials. Low to mid-frequency horizontal (0.003-4 Hz) and mid-frequency vertical (1-3 Hz) vestibulo-ocular reflex, otolith-mediated reflexes, dynamic visual acuity and balance measures were generally not influenced by age. Females had larger static subjective visual testing offset angles, longer cervical vestibular evoked myogenic potential P1 latency, faster velocity horizontal saccades, and quicker motor control latency for large backward translations than age-matched males. These reference ranges can be used to discern impairment within the auditory and vestibular pathway following traumatic brain injury in young to middle-aged adults. TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT01925963.

Effects of Secondhand Smoke Exposure on Hearing and Auditory Evoked Potentials, ABR and AMLR in Young Adults.

Population health is impacted by environmental secondhand smoke (SHS) exposure. Although the negative health effects of SHS exposure include respiratory problems in children (nonsmokers) as seen in cigarette smokers, other health impacts such as sensory function are not assumed to be the same for both passive nonsmokers and smokers. However, hearing loss was recently reported in adolescents and aging adults with SHS exposure, suggesting that SHS might impact auditory function similarly to cigarette smoking. Specific effects of SHS exposure on the central auditory system have not been fully described. To measure auditory function via pure-tone audiometry and evoked potentials in young nonsmoking adults aged 18-23 yr who reported exposure to environmental SHS. Participants were selected for the SHS-exposed (SHS-E) group first, followed by age and gender matched individuals for the SHS-unexposed (SHS-U) group. Self-reported nonsmoker status was confirmed by biochemical analysis of urine for cotinine level. Potential participants (N = 208) completed a questionnaire about health, smoking history, SHS exposure, and hearing ability. Individuals with any neurological conditions, alcohol/drug dependencies, excessive noise exposure, using certain medications, or current smokers were excluded. Twenty-two nonsmokers in excellent health consented to participate. Participants in the SHS-E group reported SHS exposure in home, work, or social settings for an extensive time period. Participants in the SHS-U group did not live with smokers and reported no SHS exposure, medication use, tinnitus, or any chemical exposures. Statistical analysis was conducted on data from 20 participants, 10 per group with a mean age of 20 yr. Participants underwent auditory procedures in one session in an IAC sound-treated room, including otoscopy, tympanometry, pure-tone threshold evaluation, auditory brainstem response per ear, and a three-channel auditory middle latency response in the right ear. The primary study outcomes were hearing thresholds measured (dB HL) at five frequencies, and evoked potential wave latencies (I, III, V, Na, Pa, Nb, Pb) and amplitudes (V-I, Na-Pa, Pa-Nb, Nb-Pb). It was hypothesized that SHS-exposed individuals would have poorer hearing sensitivity (threshold >25 dB HL) and abnormal central auditory function (longer latencies; smaller amplitudes) based on evoked potentials. Statistical analyses focused on identification of group differences in hearing and central auditory function. All participants had normal hearing sensitivity (thresholds ≤25 dB HL) with no significant group differences. The V/I amplitude ratio in the right ear was significantly decreased in SHS-exposed individuals (p < 0.05). Auditory brainstem response latencies were not significantly different between participant groups or ears. Wave Pb latency was significantly increased in SHS-exposed individuals (p < 0.01). Auditory middle latency response relative amplitudes were significantly different from each other at every electrode site (Cz, Fz, C4) but not between groups. Overall, the Na-Pa complex was highest in amplitude at all three electrode sites. This preliminary study indicated toxic effects of SHS exposure by evoked potentials with decreased V/I amplitude ratio and longer (delayed) Pb latency in young adults. Further studies should corroborate these findings to facilitate clinical recommendations.