Semin Hear 2003; 24(2): 157-158
DOI: 10.1055/s-2003-39846
ABSTRACTS OF PRESENTATIONS

Copyright © 2002 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

The Aging Ear: Results from Animal and Human Studies

John H. Mills, Bradley A. Schulte, Judy R. Dubno, Flint A. Boettcher
  • Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina
Further Information

Publication History

Publication Date:
11 June 2003 (online)

The most common causes of hearing loss are exposure to noise, aging, and the combined effects of the two. Anatomically, noise-induced hearing loss (NIHL) is characterized by a loss of sensory cells and secondary neural degeneration. Physiologically, NIHL is characterized by threshold elevations of the compound action potential of the auditory nerve, auditory brainstem response, and higher-level potentials. The endocochlear potential is most commonly unaffected. A distinctive feature of NIHL is the loss of cochlear nonlinearities, including otoacoustic emissions and two-tone rate suppression measured in single fibers of the auditory nerve. Degeneration of the stria vascularis is typically not associated with NIHL. The pathological anatomy and physiology of the aging ear is different from that associated with NIHL. The most dominant pathology is degeneration of the stria vascularis/lateral wall of the cochlea with a reduction in the endolymphatic potential from 90 to 100 mV to values as low as 10 to 20 mV. Blood supply is compromised and correlated with the extent of strial degeneration. A distinctive anatomic feature of the aging ear is the presence and normality of sensory cells except in the most basal and most apical regions. A distinctive physiological feature is the presence of otoacoustic emissions and two-tone rate suppression. There is significant degeneration of spiral ganglion cells in the presence of a normal population of sensory cells, thus suggesting an age-related primary degeneration of the auditory nerve. Thus, age-related hearing loss is not a sensorineural problem, as is NIHL, but is a vascular, metabolic, neural disorder.