Researchers report a potential treatment for noise-induced hearing loss. Loud sounds, such as those experienced by soldiers from roadside bombs, damage sensory hair cells in the inner ear and associated auditory synapses, leading to hearing loss. The mechanism of hair cell damage is well-understood, but that of synaptic damage is not. Using optical coherence tomography, John Oghalai and colleagues imaged in vivo the inner ears of mice exposed to a blast wave. The authors observed an increase in the volume of endolymph, the fluid within the cochlear duct, during the 3 hours following exposure to the blast wave. Seven days after blast exposure, the mice had significantly fewer synaptic ribbons per hair cell than unexposed mice. Increasing the solute concentration of the perilymph, the fluid in the ducts surrounding the cochlear duct, reduced endolymph volume via osmosis, and mice treated with high-solute perilymph following blast exposure lost 45-64% fewer synaptic ribbons than untreated mice. The results suggest that osmotic stabilization of fluid volume in the inner ear after noise exposure might help reduce subsequent hearing loss. According to the authors, such treatment might also help patients with Meniere's disease, which is marked by vertigo and hearing loss.
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Article #17-20121: "Osmotic stabilization prevents cochlear synaptopathy after blast trauma," by Jinkyung Kim, Anping Xia, Nicolas Grillet, Brian E. Applegate, and John S. Oghalai.
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Proceedings of the National Academy of Sciences