Cochlear synaptopathy in acquired sensorineural hearing loss: Manifestations and mechanisms

Hear Res. 2017 Jun;349:138-147. doi: 10.1016/j.heares.2017.01.003. Epub 2017 Jan 10.

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 neuropathy; Cochlear synaptopathy; Hidden hearing loss; Noise-induced hearing loss.

Publication types

  • Review
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Auditory Perception
  • Auditory Threshold
  • Cochlear Nerve / metabolism
  • Cochlear Nerve / pathology*
  • Cochlear Nerve / physiopathology
  • Glutamic Acid / metabolism
  • Hair Cells, Auditory, Inner / metabolism
  • Hair Cells, Auditory, Inner / pathology*
  • Hearing Loss, Noise-Induced / metabolism
  • Hearing Loss, Noise-Induced / pathology*
  • Hearing Loss, Noise-Induced / physiopathology
  • Hearing Loss, Noise-Induced / psychology
  • Hearing Loss, Sensorineural / metabolism
  • Hearing Loss, Sensorineural / pathology*
  • Hearing Loss, Sensorineural / physiopathology
  • Hearing Loss, Sensorineural / psychology
  • Hearing*
  • Humans
  • Nerve Degeneration
  • Noise / adverse effects
  • Risk Factors
  • Synapses / metabolism
  • Synapses / pathology*
  • Synaptic Transmission

Substances

  • Glutamic Acid