Noise-Induced Hearing Loss and Tinnitus in Milit ary Personnel

                          http://www.mathewsopenaccess.com/EMedicine-current-issue.html

Hearing loss is the most common form of sensory impairment in humans, affecting 5.3% worldwide population. Hearing is critical to the performance of military personnel and is integral to the rapid and accurate processing of speech information. Noise-induced hearing loss represents a severe impairment that reduces military effectiveness, safety, and quality of life. Military personnel work in high-noise environments, yet the Department of Defense cannot predict who is susceptible to noise-induced hearing loss and tinnitus. Of those exposed to noise, 80% may also suffer from chronic tinnitus. Despite its prevalence, there are no means to objectively measure the severity of tinnitus in those individuals. 

A fundamental understanding of the underlying mechanisms of tinnitus and its relation to noise-induced hearing loss is critical. Such an understanding may provide insight to who is at risk for each condition, allow aggressive hearing protection measures in those individuals most at risk, and create areas for treatment for those already suffering from the conditions. The current review addresses the scope of the problems of noise-induced hearing loss and tinnitus for the military, discuss the noise environments in which military personnel operate, and describe recent pharmacotherapy trials. Some recent breakthroughs in noise-induced hearing loss research are discussed along with some challenges and directions for future research on hearing loss and tinnitus.

The mammalian cochlea is the sensory organ capable of perceiving sound over a range of pressure, and discriminating both infrasonic and ultrasonic frequencies in different species. The organ of Corti is located in the cochlea of the inner ear and is responsible for the detection of sound. This organ harbours the auditory sensory epithelium, which, in humans, contains approximately 16,000 hair cells that are patterned into three rows of outer hair cells (OHCs) and one row of inner hair cells (IHCs). The cell bodies of hair cells form specialized adhesive contacts with supporting cells that adhere at their basolateral surfaces to the basilar membrane, an extracellular matrix assembly with a different molecular composition from the tectorial membrane.