Histopathologic Changes of Cochlea and Hearing Threshold Changes according to Duration of Noise-Exposure in the Rat.
- Author:
Bo Hyung KIM
1
;
Sung Ho KANG
;
Dai June LIM
;
Beob Yi LEE
;
Yong Bae LEE
Author Information
1. Department of Otolaryngology, College of Medicine Konkuk University, Chungju, Korea. bhkim@kcucc.cj.konkuk.ac.kr
- Publication Type:Original Article
- Keywords:
Noise exposure;
Outer hair cell;
Ganglion cell
- MeSH:
Animals;
Cochlea*;
Ear, Inner;
Evoked Potentials, Auditory, Brain Stem;
Ganglion Cysts;
Hair;
Hearing Loss;
Hearing*;
Microscopy, Electron, Transmission;
Noise;
Pathology;
Rats*
- From:Korean Journal of Otolaryngology - Head and Neck Surgery
1999;42(12):1490-1496
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
BACKGROUND AND OBJECTIVES: The degree of noise induced hearing loss was determined principally according to the level and duration of noise and patient's state. The purpose of this study was to investigate the cochlear histopathology and hearing threshold immediately after noise exposure according to duration of noise exposure, and finally to draw relationship between the cochlear pathology and hearing threshold. MATERIALS AND METHOD: Each group of animals (6 ears) has been exposed for 10 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 24 hours and 48 hours to an octave band of noise with a center frequency of 4000 Hz and a sound pressure level of 110 dB. After noise exposure, the hearing thresholds of the subjects were determined with auditory brainstem response (ABR) and immediately their inner ear were fixed and observed with transmission electron microscopy (TEM). RESULTS: ABR thresholds were increased according to lengthening of duration of noise exposure. TEM findings of outer hair cells, Deiters' cells and ganglion cells showed more severe degeneration according to lengthening of duration of noise exposure. Damages of all kinds of cells appeared almost at the same time. CONCLUSION: Through the foregone study, cochlear pathology was proportioned to increased hearing threshold, and the damages of outer hair cells and ganglion cells appeared almost at the same time. It seems that not only damages of outer hair cells, but also damages of ganglion cells contribute to early hearing threshold shift during continuous intense noise exposure.
