Differential Vulnerability of Inner and Outer Hair Cell Systems to Chronic Mild Hypoxia and Glutamate Ototoxicity: Insights into the Cause of Auditory Neuropathy

Sawada, Shoichi; Mori, Naoki; Mount, Richard J.; Harrison, Robert V.

doi:10.2310/7070.2001.20818

Cited by 47 publications

(31 citation statements)

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“…The MRI findings at 16 months of a thin corpus callosum, mild brain dystrophy, and slow brain maturation were consistent with a postischemic-anoxic event in the immature brain. Slow whitematter maturation, ischemia, and anoxia have also been suggested by others as possible etiologic factors in AN in high-risk infants [Harrison, 1998;Mazurek et al, 2003;Sawada et al, 2001]. In experimental studies, the induction of controlled hypoxia and/or ischemia led to a greater vulnerability and greater loss of the inner hair cells and cochlear afferent neurons (including type I) than of the outer hair cells.…”

Section: Discussionmentioning

confidence: 86%

Transient Deafness in Young Candidates for Cochlear Implants

Attias

Raveh

2007

Audiol Neurotol

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This study describes 5 infants who were diagnosed with auditory neuropathy (AN) associated with severe to profound neural hearing loss shortly after birth. However, on repetition of the tests 7–12 months later, all infants showed full or partial recovery. The follow-up electrophysiological patterns were characterized by the appearance of wave I, followed by wave III and V, reflecting synchronization of auditory pathways and improvement in auditory nerve function. Suspected causative or contributory factors were neonatal hyperbilirubinemia, hypoxia, ischemia, and central nervous system immaturity, alone or in combination. These findings indicate that lack of an auditory brain stem response does not necessarily mean no hearing and that the situation where AN exists can improve. Thus, clinicians should be made aware that although cochlear implants may yield better auditory performance when applied early, they should be considered a therapeutic option only after repeated measures have proved persistent AN, and no child should be considered for an implant until a behavioral measure of hearing has been obtained.

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Section: Discussionmentioning

confidence: 86%

Transient Deafness in Young Candidates for Cochlear Implants

Attias

Raveh

2007

Audiol Neurotol

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“…In an initial period of strial dysfunction, there is a possibility of recovery, but prolonged loss of EP (when there is severe hypoxia) may result in permanent sensory damage. This notion is based on studies that have reported cochlear dysfunction with partial recovery after short periods of severe hypoxia or anoxia (e.g., Perlman et al 1959;Schulte and Schmiedt, 1992;Tabuchi et al 1998) but with permanent sensorineural hearing loss after very long periods of oxygen deprivation (e.g., Billett et al 1989;Tabuchi et al 1998;Sawada et al 2001). If the initial target of a viral infection is the stria vascularis, then with early detection and diagnosis, perhaps, some treatment for recovery is possible.…”

Section: Discussionmentioning

confidence: 99%

Cytomegalovirus (CMV) Infection Causes Degeneration of Cochlear Vasculature and Hearing Loss in a Mouse Model

Carraro

Almishaal

Hillas

et al. 2016

JARO

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Cytomegalovirus (CMV) infection is one of the most common causes of congenital hearing loss in children. We have used a murine model of CMV infection to reveal functional and structural cochlear pathogenesis. The cerebral cortex of Balb/c mice (Mus musculus) was inoculated with 2000 pfu (plaque forming units) of murine CMV on postnatal day 3. At 6 weeks of age, cochlear function was monitored using auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measures. Histological assessment of cochlear vasculature using a corrosion cast technique was made at 8 weeks. Vascular casts of mCMV-damaged cochleas, and those of untreated control animals, were examined using scanning electron microscopy. We find very large variations in the degree of vascular damage in animals given identical viral injections (2000 pfu). The primary lesion caused by CMV infection is to the stria vascularis and to the adjacent spiral limbus capillary network. Capillary beds of the spiral ligament are generally less affected. The initial vascular damage is found in the mid-apical turn and appears to progress to more basal cochlear regions. After viral migration to the inner ear, the stria vascularis is the primary affected structure. We suggest that initial auditory threshold losses may relate to the poor development or maintenance of the endocochlear potential caused by strial dysfunction. Our increased understanding of the pathogenesis of CMV-related hearing loss is important for defining methods for early detection and treatment.

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“…Many more patients with AN have since been identified, but the underlying physiological mechanisms remain unclear and have been a major source of debate (Berlin et al 2003a;Rapin and Gravel 2003;Starr et al 2000). The sites of lesion include all possible combinations of the inner hair cell, the synapse between the inner hair cell and the auditory nerve, and the auditory nerve itself (Hallpike et al 1980;Harrison 1998;Salvi et al 1999;Sawada et al 2001;Spoendlin 1974;Starr et al 2003Starr et al , 2004. Lesion on these sites can lead to two neurophysiological manifestations, including 1) desynchronized spikes due to either demyelination in the auditory nerve (Waxman 1977) or dysfunctional synaptic transmission between the inner hair cells and the auditory nerve (Glowatzki and Fuchs 2002) and 2) reduced spike count due to either receptor loss (Harrison 1998;Salvi et al 1999) or axonal loss (Starr et al 2003).…”

Section: Physiological Mechanismsmentioning

confidence: 99%

“…Desynchronized neural discharge can occur due to demyelination and ion channel dysfunction in the auditory nerve (Starr et al 1998;Waxman 1977) and/or dysfunctional synaptic transmission between the inner hair cells and the auditory nerve (Fuchs et al 2003;Glowatzki and Fuchs 2002). Loss of the neural input to the brain can occur due to inner hair cell loss (Harrison 1998;Salvi et al 1999;Sawada et al 2001) and/or auditory nerve loss (Hallpike et al 1980;Spoendlin 1974;Starr et al 2003). Although the term AN has been widely accepted clinically as a diagnosis, alternative terms such as "auditory dys-synchrony" have been suggested to reflect the common phenomenon that likely has several underlying pathologies (Berlin et al 2003a;Rapin and Gravel 2003).…”

Section: Introductionmentioning

confidence: 99%

Perceptual Consequences of Disrupted Auditory Nerve Activity

Zeng

Kong²,

Michalewski³

et al. 2005

Journal of Neurophysiology

282

275

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. Perceptual consequences of disrupted auditory nerve activity were systematically studied in 21 subjects who had been clinically diagnosed with auditory neuropathy (AN), a recently defined disorder characterized by normal outer hair cell function but disrupted auditory nerve function. Neurological and electrophysical evidence suggests that disrupted auditory nerve activity is due to desynchronized or reduced neural activity or both. Psychophysical measures showed that the disrupted neural activity has minimal effects on intensity-related perception, such as loudness discrimination, pitch discrimination at high frequencies, and sound localization using interaural level differences. In contrast, the disrupted neural activity significantly impairs timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, temporal modulation detection, backward and forward masking, signal detection in noise, binaural beats, and sound localization using interaural time differences. These perceptual consequences are the opposite of what is typically observed in cochlear-impaired subjects who have impaired intensity perception but relatively normal temporal processing after taking their impaired intensity perception into account. These differences in perceptual consequences between auditory neuropathy and cochlear damage suggest the use of different neural codes in auditory perception: a suboptimal spike count code for intensity processing, a synchronized spike code for temporal processing, and a duplex code for frequency processing. We also proposed two underlying physiological models based on desynchronized and reduced discharge in the auditory nerve to successfully account for the observed neurological and behavioral data. These methods and measures cannot differentiate between these two AN models, but future studies using electric stimulation of the auditory nerve via a cochlear implant might. These results not only show the unique contribution of neural synchrony to sensory perception but also provide guidance for translational research in terms of better diagnosis and management of human communication disorders.

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Differential Vulnerability of Inner and Outer Hair Cell Systems to Chronic Mild Hypoxia and Glutamate Ototoxicity: Insights into the Cause of Auditory Neuropathy

Cited by 47 publications

References 0 publications

Transient Deafness in Young Candidates for Cochlear Implants

Transient Deafness in Young Candidates for Cochlear Implants

Cytomegalovirus (CMV) Infection Causes Degeneration of Cochlear Vasculature and Hearing Loss in a Mouse Model

Perceptual Consequences of Disrupted Auditory Nerve Activity

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