Presbyacusis and the auditory brainstem response

Hearing Evaluation in Patients with Exfoliative and Primary Open-Angle Glaucoma

Objective. The aim of this prospective study was to audiologically evaluate consecutive glaucoma patients with or without exfoliation.

Study Design. Prospective study.

Setting. Glaucoma Unit and Audiology Department at a university hospital.

Subjects and Methods. Consecutive subjects with exfoliative glaucoma (XFG) or primary open-angle glaucoma (POAG) aged between 50 and 70 years were enrolled. Auditory thresholds at 0.5, 1.0, 2.0, 4.0, and 8.0 Hz were measured bilaterally. Cochlear activity was assessed by recording distortion product otoacoustic emissions (DPOEs). Functional changes in the retrocochlear auditory pathway were evaluated by auditory brainstem responses (ABRs).

Results. One hundred and ten patients with XFG and 85 patients with POAG who presented in a glaucoma clinic were investigated. The mean age of study patients was 66.2 ± 5.6 years; range, 50-70 years). The odds of pathologic ABR central transmission time (interpeak latencies I-III, III-V, and I-V and waves I, III, and V) were 4.34 times higher in patients with XFG than in patients with POAG (95% confidence interval [CI], 2.22-8.49; P < .001). This significant association remained after adjusting for sex and age (odds ratio [OR] 4.12; 95% CI, 2.07-8.22; P < .001). Furthermore, the odds of ABR remained significantly higher in patients with XFG than in patients with POAG (OR 4.36; 95% CI, 2.10-9.06; P < .001) after controlling for systemic diseases (arterial hypertension, coronary heart disease, high cholesterol, and stroke).

Conclusion. In the first study to compare XFG and POAG monitoring of the peripheral and central auditory pathway, it has been documented that XFG patients show a greater prevalence of retrocochlear pathology.

[Relationship between sensory hearing loss and depression in elderly people: a literature review]

Advances in health, social and economic conditions in the developed countries have increased life expectancy and the number of elderly people. However, although health conditions have improved, age-related diseases are still increasing. One of the most common ailments is the age-related hearing loss, which has several pathophysiological causes and may be influenced by age-related morpho-functional changes. Hearing loss may also have underlying conditions in each individual. Sensory hearing loss tends to negatively affect the quality of life of the elderly, interfering with their capacity to communicate and affecting mood and the level of participation in social life. This may be independent of the cognitive and physical state of individuals, which in the long term and in many cases may end in depression. Detection and early treatment of hearing loss is an important bio-psycho-social benefit to the elderly.

Deletion of the mouse homolog of KCNAB2, a gene linked to monosomy 1p36, results in associative memory impairments and amygdala hyperexcitability

Ablation of the distal end of the short arm of chromosome 1 [1p36 deletion syndrome (1p36DS)] is one of the most commonly occurring terminal deletion syndromes in humans, occurring in ∼1 in 5000 newborns. Subjects with 1p36DS manifest a wide range of clinical features including growth delay, congenital heart defects, and craniofacial dysmorphism. In addition, individuals with 1p36DS often exhibit some form of neurological abnormality and are typically cognitively impaired. Although there is significant variability with regard to the extent of the deletion, several genes have been mapped to region 1p36 that are known to regulate neuronal function. One such gene--KCNAB2--encodes the potassium channel auxiliary subunit Kvβ2, which has been previously shown to modulate voltage-gated potassium currents in heterologous expression systems. Here, we present experiments characterizing mice in which the ortholog of KCNAB2 was deleted. We find that deletion of Kcnab2 in mice leads to deficits in associative learning and memory. In addition, using whole-cell current-clamp, we find that deletion of Kcnab2 leads to a reduction in the slow afterhyperpolarization following a burst of action potentials and a concomitant increase in neuronal excitability in projection neurons in the lateral nucleus of the amygdala. Our results suggest that loss of Kvβ2 likely contributes to the cognitive and neurological impairments observed in 1p36DS patients.

Standardization of brainstem auditory evoked potential using a new device

BACKGROUND

Standardization of Brainstem Auditory Evoked Potential (BAEP) using a new device.

AIM

To standardize BAEP responses using a new device developed (NDD) in Brazil.

METHOD

Analysis of absolute latencies, interpeaks and wave amplitudes of BAEP, using a new device developed to study normal-hearing groups (91 adults) and individuals (15 adults) with bilateral neurosensory hearing loss. Responses obtained in the EP15 hearing device/Interacoustics and the NDD were compared. For this, the following paramenters were used: non-filtered click of 100 microsecond (µs), totaling 2000 stimuli in rarefied polarity, stimulation frequency of 13.1 clicks/s, intensity of 80 decibels normalized hearing level (dB nHL), with a window of 10 milliseconds and bandpass filter between 100 and 3000 Hertz (Hz). Significance level was set at 0.05.

RESULTS

Absolute latency and interpeak means for 76 normal-hearing individuals with the NDD were: wave I=1.50, III=3.57, V=5.53, I-III=2.06, III-V=1.96 and I-V=4.02. When analyzing results according to gender, there was a statistically significant difference for the absolute latencies of waves III and V and in interpeaks I-III and I-V. Mean amplitude value of wave I=0.384 microvolt (µV) and of wave V=0.825 µV. There was no statistically significant difference between the absolute latencies and interpeaks of the two devices in the same individual.

CONCLUSION

The components of BAEP with the NDD in normal-hearing subjects were similar regarding the tested ears, with statistically lower latencies in women. The BAEP latencies in the same individual with NDD were similar to those obtained with the EP15 / Interacoustics. Normal values of BAEP were obtained in normal-hearing adults.

Age-related changes in the central auditory system: comparison of D-galactose-induced aging rats and naturally aging rats

One of the most common complaints among aging individuals is difficulty in understanding speech in a compromised listening environment, such as when background noise is present. Age-related hearing loss (presbycusis) is associated with both peripheral and central neural processing deficits, as it occurs even in those with only a mild peripheral hearing impairment. The current study was designed to investigate potential causative mechanisms of this impairment by using a rat model in which presbycusis is inducible by administration of D-galactose (D-gal). One group of these rats was injected subcutaneously with 150 mg D-gal daily for 8 weeks, while control animals received vehicle only. These groups were compared to naturally aged rats (24 months) that had received no other treatment. Central auditory function of the three groups was evaluated by measuring the auditory brainstem response (ABR) and middle latency response (MLR). A TaqMan real time PCR assay was used to quantify a 4834-bp deletion in the mitochondrial DNA (mtDNA) of the auditory cortex (AC), inferior colliculus (IC) and cochlear nucleus (CN). We assessed changes in lipid peroxidation levels and apoptosis rates, and examined pathological changes corresponding to D-gal-induced aging and natural aging. Both groups of aged rats exhibited delayed ABR latencies (III, IV, V), MLR Pa latency, and I-IV interpeak latency. Moreover, increased mtDNA 4834 bp deletion rates, lipid peroxidation levels, rates of neuronal apoptosis and neurodegenerative changes in the AC, IC and CN were similar among the D-gal induced and NA rats. However, the threshold of ABR in the D-gal group showed no significant change from the control group. These observations suggest that age-related central auditory dysfunction and its corresponding pathological changes are present in both naturally aging rats and the D-gal mimetic aging model. Oxidative stress, large-scale mtDNA 4834 bp deletion, and apoptosis are likely to be involved in the progressive weakening of the central auditory system associated with the aging process.

Effects of aging on inner ear morphology in dogs in relation to brainstem responses to toneburst auditory stimuli

BACKGROUND

Age-related hearing loss (ARHL) is the most common form of hearing loss in humans and is increasingly recognized in dogs.

HYPOTHESIS

Cochlear lesions in dogs with ARHL are similar to those in humans and the severity of the histological changes is reflected in tone audiograms.

ANIMALS

Ten geriatric dogs (mean age: 12.7 years) and three 9-month-old dogs serving as controls for histological analysis.

METHODS

Observational study. Auditory thresholds were determined by recording brainstem responses (BERA) to toneburst auditory stimuli (1, 2, 4, 8, 12, 16, 24, and 32 kHz). After euthanasia and perfusion fixation, the temporal bones were harvested and processed for histological examination of the cochleas. The numbers of outer hair cells (OHCs) and inner hair cells (IHCs) were counted and the spiral ganglion cell (SGC) packing density and stria vascularis cross-sectional area (SVCA) were determined.

RESULTS

A combination of cochlear lesions was found in all geriatric dogs. There were significant reductions (P .001) in OHC (42%, 95% confidence interval [CI]; 24-64%) and IHC counts (21%, 95% CI; 62-90%) and SGC packing densities (323, 95% CI; 216-290) in the basal turn, SVCA was smaller in all turns. The greatest reduction in auditory sensitivity was at 8-32 kHz.

CONCLUSIONS AND CLINICAL IMPORTANCE

ARHL in this specific population of geriatric dogs was comparable histologically to the mixed type of ARHL in humans. The predominance of histological changes in the basal cochlear turn was consistent with the large threshold shifts observed in the middle- to high-frequency region.

Relation between derived-band auditory brainstem response latencies and behavioral frequency selectivity

Derived-band click-evoked auditory brainstem responses (ABRs) were obtained for normal-hearing (NH) and sensorineurally hearing-impaired (HI) listeners. The latencies extracted from these responses, as a function of derived-band center frequency and click level, served as objective estimates of cochlear response times. For the same listeners, auditory-filter bandwidths at 2 kHz were estimated using a behavioral notched-noise masking paradigm. Generally, shorter derived-band latencies were observed for the HI than for the NH listeners. Only at low click sensation levels, prolonged latencies were obtained for some of the HI listeners. The behavioral auditory-filter bandwidths accounted for the across-listener variability in the ABR latencies: Cochlear response time decreased with increasing filter bandwidth, consistent with linear-system theory. The results link cochlear response time and frequency selectivity in human listeners and offer a window to better understand how hearing impairment affects the spatiotemporal cochlear response pattern.

Prevalence and audiological characteristics in individuals with auditory neuropathy/auditory dys-synchrony

The objectives of this study were to (a) estimate the prevalence of auditory dys-synchrony in Mysore, a city of one million population in Southern India and, (b) present the results of audiological testing of this clinical population as well as the relationship between these figures. A register-based study design was employed wherein the results of audiological tests of all patients who visited the Department of Audiology, All India Institute of Speech and Hearing between January 2000 and December 2003 were reviewed. Results showed that the prevalence of auditory dys-synchrony was around 1 in 183 in individuals with sensory neural hearing loss. Behavioural thresholds and speech identification scores were variable. Around 60% of the individuals had no measurable speech identification scores. There was no relation between the hearing thresholds and speech identification scores or between otoacoustic emissions and speech identification scores. These results indicate that auditory dys-synchrony is not an extremely rare disorder.

Brainstem evoked response audiometry in normal hearing subjects

Brainstem Evoked Response Audiometry (BERA) is an objective and non-invasive method of hearing assessment which detects electrical activity from the inner ear to the inferior colliculus.

Aim

To assess the hearing pathway in normal hearing individuals and compare differences associated with gender, age and ear side (left and right). Study Design: A retrospective study.

Materials and Methods

Sixty normal hearing individuals, aged between 09 and 66 years old, were subjected to clinical ENT examination and audiologic tests.

Results

Wave latencies differed significantly between males and females, although there were no differences regarding right or left ear sides. Comparing latency averages regarding age and gender we noticed important differences. By the same token, significant differences were also seen comparing this study with the information present in the handbook of the BERA device used and results published by Fukuda, in another study.

Conclusion

Knowing the great importance of BERA, it is crucial that each service develops its own standards in order to enhance the accuracy of the electrophysiological diagnosis of the hearing pathway.

Effects of aging on brainstem responses to toneburst auditory stimuli: a cross-sectional and longitudinal study in dogs

BACKGROUND

It is assumed that the hearing of dogs becomes impaired with advancing age, but little is known about the prevalence and electrophysiologic characteristics of presbycusis in this species.

HYPOTHESIS

As in humans, hearing in dogs becomes impaired with aging across the entire frequency range, but primarily in the high-frequency area. This change can be assessed quantitatively by brainstem-evoked response audiometry (BERA).

ANIMALS

Three groups of 10 mixed-breed dogs with similar body weights but different mean ages were used. At the start of the study, the mean age was 1.9 years (range, 0.9-3.4) in group I, 5.7 years (3.5-7) in group II, and 12.7 years (11-14) in group III.

METHODS

In a cross-sectional study, the BERA audiograms obtained with toneburst stimuli were compared among the 3 groups. In a longitudinal study, changes in auditory thresholds of group II dogs were followed for 7 years.

RESULTS

Thresholds were significantly higher in group III than in groups I and II at all frequencies tested, and higher in group II than in group I at 4 kHz. The audiograms in group II indicated a progressive increase in thresholds associated with aging starting around 8-10 years of age and most pronounced in the middle- to high-frequency region (8-32 kHz).

CONCLUSIONS AND CLINICAL IMPORTANCE

Age-related hearing loss in these dogs started around 8-10 years of age and encompassed the entire frequency range, but started and progressed most rapidly in the middle- to high-frequency area. Its progression can be followed by BERA with frequency-specific stimulation.

Tympanometry in rhesus monkeys: effects of aging and caloric restriction

Caloric restriction is the only known method of increasing lifespan in laboratory animals. The present study was conducted as part of a larger investigation into the effect of caloric restriction on longevity of rhesus monkeys as a model for human aging. This study focused on the effects of caloric restriction and aging on measures of middle-ear function measured with tympanometry. Peak compensated static acoustic admittance (peak Y(tm)) tended to be reduced with aging. For tympanometric width (TW), the effect of age was significant with TW increasing with age. Males had a trend of narrower TW than females. A significant age by sex interaction indicated that TW for males stays relatively constant, whereas TW for females increases with age. The equivalent ear canal volume (V(ea)) was significantly larger in male monkeys than in female monkeys, and marginally larger for the control monkeys than for the caloric restricted monkeys. These results parallel many findings in middle-ear function in aging humans. Longitudinal studies are planned.

Age-related differences in sensitivity to small changes in frequency assessed with cortical evoked potentials

As part of an ongoing study of age-related changes in auditory processing, sensitivity to small changes in frequency were assessed using the cortical auditory evoked potential, P1-N1-P2, in younger and older adults with normal hearing. Behavioral measures have shown age-related differences in intensity and frequency discrimination that are larger at lower than higher frequencies. However, substantial individual differences and equivocal results among studies have been reported. This variability may reflect differences in tasks and procedures, as well as subject variables, such as hearing sensitivity and level of attention. To minimize these subject variables, the P1-N1-P2 response was investigated using a passive listening paradigm. Subjects were 10 younger and 10 older adults. The P1-N1-P2 was elicited by a 150-ms change in frequency in otherwise continuous 500-Hz and 3000-Hz pure tones presented at 70 dB SPL. P1-N1-P2 threshold was defined as the smallest change in frequency needed to evoke a P1-N1-P2 response. Furthermore, a frequency-dependent aging effect was observed for P1-N1-P2 thresholds, such that older subjects were significantly less sensitive to the frequency change than younger subjects, with significantly larger age-related differences at 500 Hz than at 3000 Hz. Age-related changes in response latencies and amplitude of the P1-N1-P2 response were also evident at 500 and 3000 Hz. These results are consistent with age-related changes in the central auditory system and suggest that changes in frequency discrimination abilities of older adults may be, in part, related to changes in preattentive levels of auditory processing.

Linear and nonlinear changes in the auditory brainstem response of aging humans

OBJECTIVE

This experiment was designed to characterize the changes in linear and nonlinear temporal interactions in the aging auditory brainstem of humans using maximum length sequence (MLS) stimulation.

METHODS

The MLS technique uses a quasi-random sequence of clicks and silences to determine the linear (linear averaging of single responses) and nonlinear (interactions between pairs or triplets of responses) temporal interactions in the auditory brainstem response (ABR). A group of 30 normal hearing females aged between 11 and 61years were tested. They were divided in three groups: young (<24years); middle (24-41years) and old (>41years).

RESULTS

The linear component showed a decrease in wave 5 amplitude with age which could also be related to increased thresholds for higher frequencies. The nonlinear component of the MLS-ABR showed significant differences between middle and old groups for wave 1 and 5 latencies and inter-wave interval (1-5).

CONCLUSIONS

The results suggest that the linear and nonlinear components of the MLS-ABR could be more sensitive to changes occurring in the auditory system before any functionally significant changes in hearing status.

SIGNIFICANCE

The nonlinear components of the auditory brainstem could be used as an investigative tool to assess early changes in the aging auditory brainstem in young middle-aged women.

Potenciais evocados auditivos em indivíduos acima de 50 anos de idade

TEMA: potenciais evocados auditivos. OBJETIVO: descrever os resultados dos potenciais evocados auditivos de tronco encefálico (PEATE), potenciais evocados auditivos de média latência (PEAML) e potencial cognitivo (P300) em indivíduos acima de 50 anos de idade. MÉTODO: este estudo foi desenvolvido no Laboratório de Investigação Fonoaudiológica em Potenciais Evocados Auditivos do Curso de Fonoaudiologia, do Departamento de Fisioterapia, Fonoaudiologia e Terapia Ocupacional da FMUSP. Foram avaliados 24 pacientes (45 orelhas) por meio do PEATE e do P300, sendo que apenas 18 destes pacientes (36 orelhas) foram avaliados por meio do PEAML. Todos os indivíduos encontravam-se na faixa etária de 51 a 74 anos de idade, divididos em três grupos:GI (50 - 59 anos), GII (60 - 69 anos) e GIII (70 a 79 anos) e apresentavam audição normal ou até perda auditiva neurossensorial de grau moderadamente severo no PEATE e de grau moderado no PEAML e no P300. A faixa de frequências avaliadas no PEATE e no PEAML abrangeu 3000 a 6000 Hz, enquanto que no P300 a faixa foi de 1000 a 1500Hz. Para a análise estatística dos dados foram utilizados os testes estatísticos de Kruskal-Wallis, Mann-Whitney e igualdade de duas proporções. RESULTADOS: observaram-se diferenças estatisticamente significantes entre os grupos simultaneamente para o interpico I -V no PEATE e para a latência da onda Na no PEAML, sendo que no PEATE foi o GIII que provocou a diferença e no PEAML foi o GI. Evidenciou-se diferença estatisticamente significante entre os grupos simultaneamente para a latência do componente P300. Verificou-se, também, alterações consideráveis em relação à qualidade dos traçados dos potenciais evocados auditivos, indicando uma forte correlação entre piora na qualidade do traçado e aumento da idade. CONCLUSÃO: o processo de envelhecimento do sistema auditivo afeta progressivamente as vias auditivas ao longo do tronco encefálico e lobo temporal.

Cumulative lifelong alcohol consumption alters auditory brainstem potentials

BACKGROUND

Alcohol is one of the most widely abused substances in the United States and Europe. It is believed that alcohol causes brain damage that may influence the central auditory tracts. Brainstem auditory evoked potentials (BAEPs) are a common method for measuring central auditory pathways. Therefore, the influence of cumulative lifelong alcohol consumption on BAEPs in subjects with normal hearing was investigated both qualitatively and quantitatively.

METHODS

BAEPs were measured in 38 male subjects, 19 of whom were head and neck tumor patients with an ECOG (Eastern Cooperative Oncology Group) scale of zero and 19 plastic surgery patients. A self-report questionnaire on alcohol and nicotine consumption together with blood tests and pure tone audiometry were obtained for all subjects before the BAEP measurement.

RESULTS

The alcohol consumption of the head and neck tumor patients corresponded to high-risk, dangerous, and risky alcohol consumption behavior, whereas that of the plastic surgery patients corresponded to risky and low-risk consumption behavior. In this way, a wide spectrum of alcohol consumption was covered. The latency I-V of the high-risk, dangerous, and risky drinkers was found to be significantly delayed compared with low-risk drinkers. A logarithmic relationship between BAEP latencies and cumulative lifelong alcohol consumption was obtained.

CONCLUSION

Alcohol consumption leads to damage in the brainstem. The logarithmic behavior between BAEP latencies and cumulative lifelong alcohol consumption reveals that even alcohol consumption within the range of low-risk drinkers may alter auditory evoked brainstem potentials significantly.

Loss of Kv3.1 tonotopicity and alterations in cAMP response element-binding protein signaling in central auditory neurons of hearing impaired mice

The promoter for the kv3.1 potassium channel gene is regulated by a Ca2+-cAMP responsive element, which binds the transcription factor cAMP response element-binding protein (CREB). Kv3.1 is expressed in a tonotopic gradient within the medial nucleus of the trapezoid body (MNTB) of the auditory brainstem, where Kv3.1 levels are highest at the medial end, which corresponds to high auditory frequencies. We have compared the levels of Kv3.1, CREB, and the phosphorylated form of CREB (pCREB) in a mouse strain that maintains good hearing throughout life, CBA/J (CBA), with one that suffers early cochlear hair cell loss, C57BL/6 (BL/6). A gradient of Kv3.1 immunoreactivity in the MNTB was detected in both young (6 week) and older (8 month) CBA mice. Although no gradient of CREB was detected, pCREB-immunopositive cells were grouped together in distinct clusters along the tonotopic axis. The same pattern of Kv3.1, CREB, and pCREB localization was also found in young BL/6 mice at a time (6 weeks) when hearing is normal. In contrast, at 8 months, when hearing is impaired, the gradient of Kv3.1 was abolished. Moreover, in the older BL/6 mice there was a decrease in CREB expression along the tonotopic axis, and the pattern of pCREB labeling appeared random, with no discrete clusters of pCREB-positive cells along the tonotopic axis. Our findings are consistent with the hypothesis that ongoing activity in auditory brainstem neurons is necessary for the maintenance of Kv3.1 tonotopicity through the CREB pathway.