Causes of Hearing Loss in Adults
Hearing loss in adults has many causes such as exposure to noise, disease or infection, ototoxic drugs, tumours, trauma and the aging process.
Presbycusis is the most common cause of sensory hearing loss in the adult population. This loss is caused by some degenerative changes (in the auditory system) associated with the aging process. The hearing loss is progressive in nature with the high frequencies affected first. While the process begins after age 20-30, it is often at ages 55 to 65 that the high frequencies in the speech range begin to be affected.
Noise-Induced Hearing Loss
This is the second most common cause of acquired sensorineural hearing loss. Prolonged exposure to loud noise causes damage to the hair cells in the cochlea and results in this type of permanent hearing loss. The noise-induced hearing loss usually develops gradually and painlessly.
Sometimes the hearing loss can occur as a result of acoustic trauma, or a single exposure or very few exposures to very high levels of sound. When this happens, a complete breakdown of the Organ of Corti in the inner ear occurs. When the hair cells become damaged from prolonged exposure to loud noises such as music, machines, motors and other noise producing equipment or to a single but very loud noise exposure such as gunfire or an explosion, they are unable to be stimulated properly by an incoming sound signal. Once these hair cells have become damaged there is no way for them to be repaired.
This is the condition often referred to as an ear infection. When otitis media occurs, fluid accumulates behind the eardrum in the middle ear space. This space is normally air filled in a healthy ear. The fluid arises because of the inability of the Eustachian tube to adequately function and to keep the pressure equalised to atmospheric pressure in the middle ear space. Eustachian tube dysfunction can be the result of allergies, infection in the upper respiratory tract.
Drugs used to treat some diseases are damaging to the auditory system (ototoxic) and cause hearing loss. The more common drugs that are particularly toxic to the ear are certain antibiotics (such as Streptomycin, Kanamycin, Neomycin), Salicylates in large quantities (drugs containing aspirin), and quinine. Some drugs used in chemotherapy regimens are reported to be ototoxic. The damage caused by these drugs often depends on the dose administered and length of time used and is usually permanent.
Sudden Hearing Loss
This is an abrupt loss of hearing. Sudden hearing loss of known causes may be due to drugs, trauma, infection, or disease. There are, however, many instances when no cause can be found. There are two theories as to what happens in these cases: Vascular Occlusion which is the abrupt interference of blood supply to the cochlea and Viral Labyrinthitis (viral infection of the inner ear), which produces damage to the inner ear structures.
This is a progressive ear disease involving the middle ear bony capsule, specifically affecting the movement of the stapes (one of the three small bones in the middle ear).
Trauma can cause a conductive, sensorineural or even a mixed hearing loss. Damage can occur to
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