Sensorineural hearing loss (SNHL) is the most common type of hearing loss that occurs in adult populations. Causes may vary however the anatomy effected is the cochlea. There are several structures within the inner ear such as inner and outer hair cells. There are also fluids that have different chemical compositions. These structures and fluids allow sound and balance information to be transmitting along to the brain for awareness and comprehension. Changes to these structures or chemicals may lead to hearing loss or other perceptual changes (i.e., tinnitus, dizziness, ear pressure).
Genetics, noise exposure (instant or cummulative), aging or metabolic changes, injuries, blood clots, disease, and medications cause changes or damage to outer and inner hair cells.
Outer hair cells can be viewed as our body’s natural hearing aid. Granted the outer ear and middle ear amplify sounds to an extent, the outer hair cells give the inner ear the boost to hear very soft sounds. When they are damaged they cannot be repaired.
The inner hair cells we generally attribute to working as a microphone. A simple way of understanding this is to imagine that the outer hair cells are amplifiers that provide sound to the inner hair cell. The inner hair cell connects to the hearing nerve, which carries the signal to the brain.
The function of the inner ear, to an extent, can be measured with special equipment in an audiological or otolaryngological office. Most audiologists are equipped to measure the function of the outer hair cells via otoacoustic emissions. This type of testing provides valuable information to diagnose sensorineural hearing loss.