Sensorineural hearing impairment is hearing loss caused by damage to the structures of the inner ear, the auditory nerve, or the auditory cortex in the brain, which is responsible for interpreting signals from the auditory nerve. It's different from conductive hearing impairment, which normally occurs in the middle or outer ear, and is usually the result of a blockage of the ear canal that stops sound waves from reaching the inner ear. Sensorineural hearing loss can occur due to aging, infections, tumors, the use of certain drugs, or congenital deformities, among other things. This type of hearing loss can be difficult to prevent. Patients can usually benefit from one of many treatment options to improve impaired hearing.
Exposure to loud sounds may be the most common cause of sensorineural hearing impairment. Exposure to very loud noise, such as industrial or construction noises, or even loud music, can damage the sensory cells of the cochlea, leading to hearing impairment. Noise-related hearing impairment can be prevented by avoiding loud noises, or by wearing ear protection during exposure to loud noises.
Age is another common factor contributing to sensorineural hearing impairment. The structures of the inner ear can gradually wear out over the years, leading to age-related sensorineural hearing loss. This type of hearing loss is known as presbycusis, and it usually begins around age 20. Presbycusis advances so slowly, however, that patients often experience no noticeable impairment in hearing until they reach their senior years.
Ear infections can also cause hearing impairment. Often, the hearing impairment associated with ear infections is conductive, and stems from the build-up of fluids in the ear canal. Ear infections that aren't treated, however, can spread to the inner ear, damaging the structures there.
Other conditions that can contribute to sensorineural hearing impairment include otosclerosis, a congenital disease characterized by overgrowth of the bone surrounding the structures of the inner ear. This bone overgrowth can eventually interfere with the structures responsible for transmitting sound to the auditory nerve, and can lead to total deafness. Autoimmune disorders, including lupus and rheumatoid arthritis, can lead to an immune reaction that damages the auditory cells of the cochlea, causing progressive hearing impairment. The use of certain prescription drugs, including chemotherapy drugs, can contribute to sensorineural hearing loss by damaging the auditory cells in the cochlea. Radiation therapy can also damage these cells, and it can damage the auditory cortex in the brain.
Hearing aids can help relieve the symptoms of sensorineural hearing impairment in many patients. Surgery can help some, such as those suffering from otosclerosis, to regain some of their hearing. For those with severe hearing loss, cochlear implants can help send sound signals to the auditory nerve and the brain's auditory cortex. Lip reading, sign language, closed captioning, and lighted alarm systems for telephones and doorbells can help those with severe hearing impairment cope with their condition.