Experimental vibratory damage of the inner ear

Area of Science:

• Ototoxicology
• Neuroscience
• Audiology

Background:

• Whole-body vibration (WBV) is prevalent in occupational settings.
• Potential ototoxic effects of WBV exposure require investigation.
• Understanding WBV's impact on the inner ear is crucial for hearing health.

Purpose of the Study:

• To investigate the effects of sinusoidal whole-body vibration on guinea pig inner ear structures.
• To correlate vibration exposure duration with observed morphological and functional changes.
• To elucidate the mechanism of hearing loss associated with WBV.

Main Methods:

• 40 guinea pigs exposed to sinusoidal vibration (10 Hz/5 mm/1.4 g rms) for 1-6 months.
• Cochlear microphonic measurements at various sound levels and frequencies.
• Morphological analysis of hair cells and acoustic nerve fibers using scanning and transmission electron microscopy.

Main Results:

• Vibration-induced changes observed in all experimental group inner ears.
• Progressive hair cell damage, starting at the apex and moving towards the base.
• Myelin sheath alterations in acoustic nerve fibers, characterized by decreased electrodensity.
• Changes in hair cells and nerve fibers occurred simultaneously and independently, correlated with exposure duration.

Conclusions:

• WBV exposure causes significant damage to inner ear structures, including hair cells and acoustic nerve fibers.
• The observed changes provide a mechanistic explanation for hearing loss in individuals exposed to WBV.
• Damage to the inner ear may lead to hearing impairment, especially affecting low and medium frequencies.