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1.
耳蜗传入突触病变在临床上可表现为听神经病、隐性听力损失、耳蜗死区病。目前除听神经病,另外两类疾病主要依据主观测试,尚无明确可用于诊断的客观方法。耳蜗电图可早期发现耳蜗传入突触病变,本文就其对耳蜗传入突触病变诊断意义进行综述,为耳蜗病变的诊断和精准治疗提供依据。 相似文献
2.
Aravindakshan Parthasarathy Jyotishka Datta Julie Ann Luna Torres Charneka Hopkins Edward L. Bartlett 《Journal of the Association for Research in Otolaryngology》2014,15(4):649-661
Hearing thresholds and wave amplitudes measured using auditory brainstem responses (ABRs) to brief sounds are the predominantly used clinical measures to objectively assess auditory function. However, frequency-following responses (FFRs) to tonal carriers and to the modulation envelope (envelope-following responses or EFRs) to longer and spectro-temporally modulated stimuli are rapidly gaining prominence as a measure of complex sound processing in the brainstem and midbrain. In spite of numerous studies reporting changes in hearing thresholds, ABR wave amplitudes, and the FFRs and EFRs under neurodegenerative conditions, including aging, the relationships between these metrics are not clearly understood. In this study, the relationships between ABR thresholds, ABR wave amplitudes, and EFRs are explored in a rodent model of aging. ABRs to broadband click stimuli and EFRs to sinusoidally amplitude-modulated noise carriers were measured in young (3–6 months) and aged (22–25 months) Fischer-344 rats. ABR thresholds and amplitudes of the different waves as well as phase-locking amplitudes of EFRs were calculated. Age-related differences were observed in all these measures, primarily as increases in ABR thresholds and decreases in ABR wave amplitudes and EFR phase-locking capacity. There were no observed correlations between the ABR thresholds and the ABR wave amplitudes. Significant correlations between the EFR amplitudes and ABR wave amplitudes were observed across a range of modulation frequencies in the young. However, no such significant correlations were found in the aged. The aged click ABR amplitudes were found to be lower than would be predicted using a linear regression model of the young, suggesting altered gain mechanisms in the relationship between ABRs and FFRs with age. These results suggest that ABR thresholds, ABR wave amplitudes, and EFRs measure complementary aspects of overlapping neurophysiological processes and the relationships between these measurements changes asymmetrically with age. Hence, measuring all three metrics provides a more complete assessment of auditory function, especially under pathological conditions like aging. 相似文献
3.
Aravindakshan Parthasarathy Jesyin Lai Edward L. Bartlett 《Journal of the Association for Research in Otolaryngology》2016,17(2):119-132
Listening conditions in the real world involve segregating the stimuli of interest from competing auditory stimuli that differ in their sound level and spectral content. It is in these conditions of complex spectro-temporal processing that listeners with age-related hearing loss experience the most difficulties. Envelope following responses (EFRs) provide objective neurophysiological measures of auditory processing. EFRs were obtained to two simultaneous sinusoidally amplitude modulated (sAM) tones from young and aged Fischer-344 rats. One was held at a fixed suprathreshold sound level (sAM1FL) while the second varied in sound level (sAM2VL) and carrier frequency. EFR amplitudes to sAM1FL in the young decreased with signal-to-noise ratio (SNR), and this reduction was more pronounced when the sAM2VL carrier frequency was spectrally separated from sAM1FL. Aged animals showed similar trends, while having decreased overall response amplitudes compared to the young. These results were replicated using an established computational model of the auditory nerve. The trends observed in the EFRs were shown to be due to the contributions of the low-frequency tails of high-frequency neurons, rather than neurons tuned to the sAM1FL carrier frequency. Modeling changes in threshold and neural loss reproduced some of the changes seen with age, but accuracy improved when combined with an additional decrease representing synaptic loss of auditory nerve neurons. Sound segregation in this case derives primarily from peripheral processing, regardless of age. Contributions by more central neural mechanisms are likely to occur only at low SNRs. 相似文献
4.
Annett Szibor Petteri Hyvärinen Jarmo Lehtimäki Ulla Pirvola Matti Ylikoski Antti Mäkitie 《Acta oto-laryngologica》2018,138(1):21-24
Conclusion: Music-induced acute acoustic trauma is not inevitably linked to hearing dysfunction as validated by conventional pure tone audiometry. Tinnitus is often in combination with hyperacusis. Our results point at ‘silent hearing loss’ as the underlying pathology, having afferent nerve terminal damage rather than hair cell loss as the structural correlate.Objectives: Exposure to loud music is one of the most common causes of acute acoustic trauma, which adolescents and teenagers experience by voluntary exposure to loud music of sound levels up to 110?dB(A).Methods: The clinical and psychophysical data of 104 consecutive patients with music-induced hearing disorder (MIHD) were analyzed to construct individual hearing and tinnitus profiles. In all cases, tinnitus was the presenting symptom.Results: Hearing abilities were normal in about two-thirds of the tinnitus patients. Tinnitus was experienced most often as a high-frequency tone (83%). The Tinnitus Handicap Inventory (THI) scores ranged from 0 to 94 with an average score of 43.1. Visual analog scales (VAS) were used to assess tinnitus loudness (average 42.4) and annoyance (average 54.2), and tinnitus awareness was estimated (average 60.3). All VAS values correlated strongly with the THI. Hyperacusis was present in 65% and 71% of the patients reported sleeping disorders. 相似文献
5.
Colleen G. Le Prell 《International journal of audiology》2019,58(1):S3-S32
AbstractObjective: Short-term noise exposure that induces transient changes in thresholds has induced permanent cochlear synaptopathy in multiple species. Here, the literature was reviewed to gain translational insight into the relationships between noise exposure, ABR metrics, speech-in-noise performance and TTS in humans.Design: PubMed-based literature search, retrieval and review of full-text articles. Study Sample: Peer-reviewed literature identified using PubMed search.Results: Permanent occupational noise-induced hearing loss (NIHL) is frequently accompanied by abnormal ABR amplitude and latency. In the absence of NIHL, there are mixed results for relationships between noise exposure and ABR metrics. Interpretation of speech-in-noise deficits is difficult as both cochlear synaptopathy and outer hair cell (OHC) loss can drive deficits. Reductions in Wave I amplitude during TTS may reflect temporary OHC pathology rather than cochlear synaptopathy. Use of diverse protocols across studies reduces the ability to compare outcomes across studies.Conclusions: Longitudinal ABR and speech-in-noise data collected using consistent protocols are needed. Although speech-in-noise testing may not reflect cochlear synaptopathy, speech-in-noise testing should be completed as part of a comprehensive test battery to provide the objective measurement of patient difficulty. 相似文献
6.
In mammals, hair cells and spiral ganglion neurons (SGNs) in the cochlea together are sophisticated “sensorineural” structures that transduce auditory information from the outside world into the brain. Hair cells and SGNs are joined by glutamatergic ribbon‐type synapses composed of a molecular machinery rivaling in complexity the mechanoelectric transduction components found at the apical side of the hair cell. The cochlear hair cell ribbon synapse has received much attention lately because of recent and important findings related to its damage (sometimes termed “synaptopathy”) as a result of noise overexposure. During development, ribbon synapses between type I SGNs and inner hair cells form in the time window between birth and hearing onset and is a process coordinated with type I SGN myelination, spontaneous activity, synaptic pruning, and innervation by efferents. In this review, we highlight new findings regarding the diversity of type I SGNs and inner hair cell synapses, and the molecular mechanisms of selective hair cell targeting. Also discussed are cell adhesion molecules and protein constituents of the ribbon synapse, and how these factors participate in ribbon synapse formation. We also note interesting new insights into the morphological development of type II SGNs, and the potential for cochlear macrophages as important players in protecting SGNs. We also address recent studies demonstrating that the structural and physiological profiles of the type I SGNs do not reach full maturity until weeks after hearing onset, suggesting a protracted development that is likely modulated by activity. 相似文献
7.
Methyl-CpG-binding protein 2 (MeCP2) deficiency causes Rett syndrome (RTT), a neurodevelopmental disorder characterized by severe cognitive impairment, synaptic dysfunction, and hyperexcitability. Previously we reported that the hippocampus of MeCP2-deficient mice (Mecp2−/y), a mouse model for RTT, is more susceptible to hypoxia. To identify the underlying mechanisms we now focused on the anoxic responses of wildtype (WT) and Mecp2−/y CA1 neurons in acute hippocampal slices. Intracellular recordings revealed that Mecp2−/y neurons show only reduced or no hyperpolarizations early during cyanide-induced anoxia, suggesting potassium channel (K+ channel) dysfunction. Blocking adenosine-5′-triphosphate-sensitive K+ channels (KATP-) and big-conductance Ca2+-activated K+ channels (BK-channels) did not affect the early anoxic hyperpolarization in either genotype. However, blocking Ca2+ release from the endoplasmic reticulum almost abolished the anoxic hyperpolarizations in Mecp2−/y neurons. Single-channel recordings confirmed that neither KATP- nor BK-channels are the sole mediators of the early anoxic hyperpolarization. Instead, anoxia Ca2+-dependently activated various small/intermediate-conductance K+ channels in WT neurons, which was less evident in Mecp2−/y neurons. Yet, pharmacologically increasing the Ca2+ sensitivity of small/intermediate-conductance KCa channels fully restored the anoxic hyperpolarization in Mecp2−/y neurons. Furthermore, Ca2+ imaging unveiled lower intracellular Ca2+ levels in resting Mecp2−/y neurons and reduced anoxic Ca2+ transients with diminished Ca2+ release from intracellular stores. In conclusion, the enhanced hypoxia susceptibility of Mecp2−/y hippocampus is primarily associated with disturbed Ca2+ homeostasis and diminished Ca2+ rises during anoxia. This secondarily attenuates the activation of KCa channels and thereby increases the hypoxia susceptibility of Mecp2−/y neuronal networks. Since cytosolic Ca2+ levels also determine neuronal excitability and synaptic plasticity, Ca2+ homeostasis may constitute a promising target for pharmacotherapy in RTT. 相似文献
8.
Phagocytic clearance of presynaptic dystrophies by reactive astrocytes in Alzheimer's disease 下载免费PDF全文
Angela Gomez‐Arboledas Jose C. Davila Elisabeth Sanchez‐Mejias Victoria Navarro Cristina Nuñez‐Diaz Raquel Sanchez‐Varo Maria Virtudes Sanchez‐Mico Laura Trujillo‐Estrada Juan Jose Fernandez‐Valenzuela Marisa Vizuete Joan X. Comella Elena Galea Javier Vitorica Antonia Gutierrez 《Glia》2018,66(3):637-653
Reactive astrogliosis, a complex process characterized by cell hypertrophy and upregulation of components of intermediate filaments, is a common feature in brains of Alzheimer's patients. Reactive astrocytes are found in close association with neuritic plaques; however, the precise role of these glial cells in disease pathogenesis is unknown. In this study, using immunohistochemical techniques and light and electron microscopy, we report that plaque‐associated reactive astrocytes enwrap, engulf and may digest presynaptic dystrophies in the hippocampus of amyloid precursor protein/presenilin‐1 (APP/PS1) mice. Microglia, the brain phagocytic population, was apparently not engaged in this clearance. Phagocytic reactive astrocytes were present in 35% and 67% of amyloid plaques at 6 and 12 months of age, respectively. The proportion of engulfed dystrophic neurites was low, around 7% of total dystrophies around plaques at both ages. This fact, along with the accumulation of dystrophic neurites during disease course, suggests that the efficiency of the astrocyte phagocytic process might be limited or impaired. Reactive astrocytes surrounding and engulfing dystrophic neurites were also detected in the hippocampus of Alzheimer's patients by confocal and ultrastructural analysis. We posit that the phagocytic activity of reactive astrocytes might contribute to clear dysfunctional synapses or synaptic debris, thereby restoring impaired neural circuits and reducing the inflammatory impact of damaged neuronal parts and/or limiting the amyloid pathology. Therefore, potentiation of the phagocytic properties of reactive astrocytes may represent a potential therapy in Alzheimer's disease. 相似文献
9.
《Otolaryngologic clinics of North America》2021,54(6):1093-1100
10.
Giuseppina Martella PhD Marta Maltese PhD Barbara Picconi PhD Paolo Calabresi MD Antonio Pisani MD PhD 《Movement disorders》2016,31(6):802-813
The appearance of motor manifestations in Parkinson's disease (PD) is invariably linked to degeneration of nigral dopaminergic neurons of the substantia nigra pars compacta. Traditional views on PD neuropathology have been grounded in the assumption that the prime event of neurodegeneration involves neuronal cell bodies with the accumulation of metabolic products. However, this view has recently been challenged by both clinical and experimental evidence. Neuropathological studies in human brain samples and both in vivo and in vitro models support the hypothesis that nigrostriatal synapses may indeed be affected at the earliest stages of the neurodegenerative process. The mechanisms leading to either structural or functional synaptic dysfunction are starting to be elucidated and include dysregulation of axonal transport, impairment of the exocytosis and endocytosis machinery, altered intracellular trafficking, and loss of corticostriatal synaptic plasticity. The aim of this review is to try to integrate different lines of evidence from both pathogenic and genetic animal models that, to different extents, suggest that early synaptic impairment may represent the key event in PD pathogenesis. Understanding the molecular and cellular events underlying such synaptopathy is a fundamental step toward developing specific biomarkers of early dopaminergic dysfunction and, more importantly, designing novel therapies targeting the synaptic apparatus of selective, vulnerable synapses. © 2016 International Parkinson and Movement Disorder Society 相似文献