Intratympanic administration of methylprednisolone reduces impact of experimental intensive impulse noise trauma on hearing.
CONCLUSIONS
The present findings demonstrated that intratympanic methylprednisolone (MP) reduces the impact of impulse noise trauma on hearing and in part preserves the hair cells from death 1 h after exposure to intensive impulse noise.


OBJECTIVE
To examine the treatment efficiency of intratympanic MP (IT-MP) with different methods of administration on cochlear injury induced by exposure to intensive impulse noise.


METHODS
Fifty-five guinea pigs were assigned into six groups and exposed to intensive impulse noise, i.e. 60 impulses at 165 dB SPL peak pressure with 0.5 ms duration and 2 s intervals. The auditory brainstem response (ABR) was used to examine the hearing thresholds. Cochlear morphology was examined to estimate the inner and outer hair cell loss induced by impulse noise exposure. MP was applied as a rescue agent via different modalities of administration.


RESULTS
The ABR threshold value of IT-MP1 or IT-MP4 groups significantly decreased at 4 weeks as compared with the IT-NS (IT 0.9% physiological saline) group. The ABR threshold value of the group that received intramuscular administration of MP (IM-MP) also decreased at 4 weeks as compared with the IT-NS group. Significant hair cell loss was observed at the region 40-50% from the apex in the present model. Within this region, the residual hair cell number in the IT-MP1 or IT-MP4 groups was significantly greater than that in the IT-NS group.
Zhou
Yide
Y
Department of Otolaryngology, Changhai Hospital, Shanghai, China. ydzhou111@163.com
Zheng
Hongliang
H
Shen
Xiaohua
X
Zhang
Qing
Q
Yang
Meiqin
M
D000818:Animals; D003051:Cochlea / Q000166:cytology / Q000473:pathology; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem; D005938:Glucocorticoids / Q000008:administration & dosage; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000473:pathology; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis / Q000517:prevention & control*; D007267:Injections / Q000379:methods; D007759:Labyrinth Diseases / Q000175:diagnosis / Q000517:prevention & control*; D008775:Methylprednisolone / Q000008:administration & dosage*; D018696:Neuroprotective Agents / Q000008:administration & dosage; D009622:Noise; D014432:Tympanic Membrane
D005938:Glucocorticoids; D018696:Neuroprotective Agents; D008775:Methylprednisolone