Correlation of audiometric data with changes in cochlear hair cell stereocilia resulting from impulse noise trauma.
Acta Oto-Laryngol 1982 Jan; 93(5-6):329-340
The relationship between ultrastructural changes in cochlear hair cells and hearing loss was studied in chinchillas. Four animals were exposed to impulse noise at a rate of 1 impulse per minute for 50 minutes at a peak intensity of 155 decibels. Hearing was measured before exposure, immediately after exposure, and 30 days later using the evoked response technique. Animals then were killed, and cochleas were sectioned and examined by transmission electron microscopy. The type and extent of ultrastructural damage to the sensory cells was compared with the permanent threshold shift determined by audiometric testing. Inner and outer hair cells showed a variety of alterations in sensory cell ultrastructure after exposure to impulse noise trauma, but most of the changes had no consistent pattern and were not related to hearing threshold changes. The only changes consistently correlated with hearing loss were in the outer hair cell stereocilia, and the degree of damage was related to the amount of threshold elevation. Outer hair cell stereocilia consistently were altered when the threshold was elevated 15 to 30 decibels. The stereocilia were no longer erect, and their membranes were loose and wrinkled. Stereocilia were missing in some cases and were fused in other cases with disintegration of the stereocilia rootlets. The authors conclude that impulse noise trauma may case a permanent threshold shift in hearing by altering the outer hair cell stereocilia membrane permeability, surface charge, and actin conformation.
NIOSH-Publication; NIOSH-Grant; Noise; Noise-levels; Noise-induced-hearing-loss; Hearing-tests; Hearing-impairment; Noise-waves; Acoustic-trauma;
Author Keywords: acoustic trauma; cochlear pathology; hair cell; stereocilia
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