title: Pathophysiological mechanisms and functional hearing consequences of auditory neuropathy.
abstract: The effects of inner ear abnormality on audibility have been explored since the early 20th century when sound detection measures were first used to define and quantify 'hearing loss'. The development in the 1970s of objective measures of cochlear hair cell function (cochlear microphonics, otoacoustic emissions, summating potentials) and auditory nerve/brainstem activity (auditory brainstem responses) have made it possible to distinguish both synaptic and auditory nerve disorders from sensory receptor loss. This distinction is critically important when considering aetiology and management. In this review we address the clinical and pathophysiological features of auditory neuropathy that distinguish site(s) of dysfunction. We describe the diagnostic criteria for: (i) presynaptic disorders affecting inner hair cells and ribbon synapses; (ii) postsynaptic disorders affecting unmyelinated auditory nerve dendrites; (iii) postsynaptic disorders affecting auditory ganglion cells and their myelinated axons and dendrites; and (iv) central neural pathway disorders affecting the auditory brainstem. We review data and principles to identify treatment options for affected patients and explore their benefits as a function of site of lesion.
authors.affiliation: 1 Department of Audiology and Speech Pathology, The University of Melbourne, 550 Swanston Street, Parkville 3010 Australia grance@unimelb.edu.au.
authors.forename: Gary
authors.initials: G
authors.lastname: Rance
authors.affiliation: 2 Department of Neurology, The University of California (Irvine), 200 S. Manchester Ave., Suite 206, Orange, CA 92868-4280, USA.
authors.forename: Arnold
authors.initials: A
authors.lastname: Starr
mesh_terms: D001299:Audiometry; D001309:Auditory Threshold; D003712:Dendrites / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*; D006313:Hearing Loss, Central / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology; D013136:Spiral Ganglion / Q000166:cytology / Q000503:physiopathology*
keywords: auditory brainstem response; auditory neuropathy; cochlear implant; postsynaptic; presynaptic