Acoustic Damage of the Cochlea: A Scanning and Transmission Electron Microscopic Observation

Thirty guinea pigs, 15 experimental and 15 control, exposed to two different noises with octave bandwidths of 300 to 600 Hertz and 1,000 to 2,000 Hz at 117 dB SPL. Exposure time varied from four to 24 hours. Progression in the extent of changes in the sensory cells as a result of noise exposure involved: (1) an increase in formation of blebs on the surface of the sensory hairs; (2) vesiculation proceeding to vacuolization of the smooth endoplasmic reticulum (ER) system; (3) heavy accumulation of lysosomal granules in the subcuticular region; (4) cuticular plates of the sensory cells deformed; and (5) eventual cell rupture and lysis. The space occupied by the destroyed sensory cell was immediately sealed off by the Deiter cell processes. The nerve endings impinging on the hair cell bodies did not show any great changes except for occasional myelin degeneration.