Elsevier

Hearing Research

Volume 349, June 2017, Pages 138-147
Hearing Research

Review Article
Cochlear synaptopathy in acquired sensorineural hearing loss: Manifestations and mechanisms

https://doi.org/10.1016/j.heares.2017.01.003Get rights and content
Under a Creative Commons license
open access

Highlights

  • Noise can cause rapid synaptic loss and slow degeneration of cochlear nerve fibers, even if hair cells survive.

  • Diffuse cochlear synaptopathy does not raise audiometric or ABR thresholds, but does decrease ABR amplitudes.

  • Ears exposed to ‘synaptopathic’ noise show exaggerated synaptic and neural losses as they age after exposure.

Abstract

Common causes of hearing loss in humans - exposure to loud noise or ototoxic drugs and aging - often damage sensory hair cells, reflected as elevated thresholds on the clinical audiogram. Recent studies in animal models suggest, however, that well before this overt hearing loss can be seen, a more insidious, but likely more common, process is taking place that permanently interrupts synaptic communication between sensory inner hair cells and subsets of cochlear nerve fibers. The silencing of affected neurons alters auditory information processing, whether accompanied by threshold elevations or not, and is a likely contributor to a variety of perceptual abnormalities, including speech-in-noise difficulties, tinnitus and hyperacusis. Work described here will review structural and functional manifestations of this cochlear synaptopathy and will consider possible mechanisms underlying its appearance and progression in ears with and without traditional ‘hearing loss’ arising from several common causes in humans.

Keywords

Auditory nerve
Cochlear synaptopathy
Cochlear neuropathy
Hidden hearing loss
Noise-induced hearing loss

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