Hearing loss is any degree of impairment of the ability to understand sound.A drop of more than 10 decibels (a unit measuring the loudness of sound) in what a person can hear is significant.
Hearing can be interrupted at many stages as sound waves pass through the airof the external ear, the bones of the middle ear, and the liquid of the inner ear. Hearing loss can also occur as hearing-related impulses are transmitted along the nerves to the brain, or within the brain, where the impulses may be misinterpreted.
The external ear canal can be blocked by ear wax, foreign objects, infection,and tumors. Overgrowth of bone, which occurs when the ear canal has been flushed with cold water repeatedly for years, can also narrow the passageway, making blockage and infection more likely. This condition occurs often in Northern California surfers and is therefore called "surfer's ear."
The ear drum is so thin a physician can see through it into the middle ear. Sharp objects, pressure from an infection in the middle ear, even a firm cuffing or slapping of the ear, can rupture it. It is also susceptible to pressurechanges during scuba diving.
Otitis media (an infection in the middle ear) occurs when fluid cannot escapeinto the throat because of blockage of the Eustachian tube. The pus or mucusaccumulates, dampening the motion of the small bones in the middle ear. A disease called otosclerosis can bind the bones, causing deafness.
Sensory hearing loss involves damage to the acoustic nerve, or to the Organ of Corti in the inner ear. The leading cause of sensory hearing loss is prolonged exposure to loud noise, often rock music or job-related noise. A third ofpeople over 65 have presbycusis--sensory hearing loss due to aging. Whetherinduced by noise or age, these conditions involve primarily the loss of high-frequency hearing. In most languages, it is the high-frequency sounds that define speech, so these people have trouble understanding speech over background noise. Brain infections like meningitis, drugs such as the aminoglycoside antibiotics (streptomycin, gentamycin, kanamycin, tobramycin), and Meniere's disease also cause permanent sensory hearing loss. Meniere's disease combines attacks of hearing loss with attacks of vertigo, a condition inwhich the person's surroundings seem to spin dizzily. These symptoms may occur together or separately. High doses of salicylates like aspirin and quininecan cause a temporary high-frequency loss. Prolonged high doses can lead topermanent deafness. Sensory deafness can also be caused by rubella (German measles). Sudden hearing loss--at least 30 decibels in less thanthree days--is most commonly caused by cochleitis, a viral infection.
Another category of hearing loss is neural. Damage to the acoustic nerve andthe parts of the brain involved in hearing are the most likely to produce permanent hearing loss. Strokes, multiple sclerosis, and tumors onthe acoustic nerve are all possible causes of neural hearing loss.
Hearing can also be diminished by extra sounds generated by the ear, most ofthem from the same kinds of disorders that cause diminished hearing. These sounds are referred to as tinnitus and can be ringing, blowing, clicking, or anything else that no one but the patient hears.
An examination of the ears and nose combined with simple hearing tests done in the physician's office can detect many common causes of hearing loss. If the defect is in the brain or the acoustic nerve, further neurological testingand imaging will be needed.
Conductive hearing loss, involving an interruption in the transmission of sound waves, can almost always be restored to some degree, if not completely. Matter in the ear canal can be easily removed. Surfer's ear gradually improvesif cold water is avoided or a special ear plug is used. In advanced cases, surgeons can grind away the excess bone. Middle ear infection with fluid is also simple to treat. If medications do not work, surgical drainage of the ear is accomplished through the ear drum, which heals completely. Damaged ear drums can be repaired with a tiny skin graft. Surgical repair of otosclerosis through an operating microscope can substitute tiny artificial parts for original bones in the inner ear.
Sensory and neural hearing loss, on the other hand, cannot readily be cured.Fortunately it is not often complete, so that hearing aids can help correct the problem. In-the-ear hearing aids can boost sound volume by up to 70 decibels. (Normal speech is about 60 decibels.) Also available are bone-conductionhearing aids and devices that can be surgically implanted in the inner ear.
Tinnitus can sometimes be relieved by adding white noise (like the sound of wind or waves crashing on the shore) to the environment.
Decreased hearing is such a common problem that there are legions of organizations to provide assistance. Special language training, both in lip reading and signing, special schools and camps for children are widely available.
Hearing loss may be helped by homeopathic therapies, and oral doses of essential fatty acids such as flax oil and omega 3 oil can help alleviate the accumulation of wax in the ear.
Prompt treatment and attentive follow-up of middle-ear infections in childrenwill prevent this cause of hearing loss. Control of infectious childhood diseases such as measles has greatly reduced sensory hearing loss as a complication of epidemic diseases. Laws that require protection from loud noise in theworkplace have achieved substantial reduction in noise induced hearing loss.Surfers should use the right kind of ear plugs.