Causes of Hearing Loss
Hearing loss in adults has many causes such as disease or infection, ototoxic drugs, exposure to noise, tumors, trauma, and the aging process. This loss may or may not be accompanied by tinnitus, ringing in the ears. Tinnitus can occur by itself without any hearing loss.
Some causes of hearing loss in adults are described below:
Disease or Infection
Otosclerosis is a disease involving the middle ear capsule, specifically affecting the movement of the stapes (one of the three tiny bones in the middle ear).
Meniere's disease affects the membranous inner ear and is characterized by deafness, dizziness (vertigo), and ringing in the ear (tinnitus).
Medications used to manage some diseases are damaging to the auditory system (ototoxic) and cause hearing loss. Some of the specific drugs known to be ototoxic are aminoglycoside antibiotics (such as streptomycin, neomycin, kanamycin); salicylates in large quantities (aspirin), loop diuretics (lasix, ethacrynic acid); and drugs used in chemotherapy regimens (cisplatin, carboplatin, nitrogen mustard).
Exposure to Noise
Exposure to harmful levels of noise results in noise-induced hearing loss . The prolonged exposure causes damage to the hair cells in the cochlea and results in permanent hearing loss. The noise-induced hearing loss usually develops gradually and painlessly. Hearing loss can also occur as a result of an acoustic trauma, or a single exposure or very few exposures to very high levels of sound.
An acoustic neuroma is an example of a tumor that causes hearing loss. Acoustic neuromas arise in the eighth cranial nerve (acoustic nerve). The first symptom is reduction of hearing in one ear accompanied by a feeling of fullness.
Trauma can also result in hearing loss. Examples include fractures of the temporal bone, puncture of the eardrum by foreign objects, and sudden changes in air pressure.
Loss of hearing as a result of the aging process is called presbycusis. The process involves degeneration of the inner ear (cochlea). Presbycusis can also involve other parts of the auditory system. The hearing loss is progressive in nature with the high frequencies affected first. While the process begins after age 20, it is typically at ages 55 to 65 that the high frequencies in the speech range begin to be affected.