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Hearing Loss
Hearing loss can occur very suddenly or it can develop slowly over time. When hearing loss develops slowly, the first signs may be difficulty understanding people in crowded rooms or when there is a lot of background noise. There are essentially two types of hearing loss – that associated with “nerve damage” and that associated with a defect in the ear drum or middle ear bones. To better understand hearing loss one first needs to understand how sound is “heard” by the brain.
Sound waves enter the ear canal and strike the ear drum. The ear drum then begins to vibrate. Attached to the ear drum are three small bones that are hooked together like a chain: the malleus (hammer), the incus (anvil) and the stapes (stirrup). Any defect in the ear drum (like a hole) or one of the middle ear bones can result in what's known as a conductive hearing loss. The last of the middle ear bones, the stapes, is attached to the cochlea, which is a fluid filled, sea-shell shaped structure. The stapes moves up and down like a piston and creates a fluid wave in the cochlea. The cochlea is lined by tiny hair cells that bend when a fluid wave passes. Each section of the cochlea responds to different frequencies. When the hair cells bend, they send a small spark to the hearing nerve that then connects with the brain to tell the brain that a certain frequency of sound was heard. Any defect in the cochlea, hair cells, hearing nerve or brain can result in a sensory neural hearing loss.
Patients with conductive hearing losses, whether due to defects in the ear drum or middle ear bones, have an excellent chance of having near-normal hearing with recent advances in middle ear surgery. Within the last several years, numerous synthetic bones have become available to replace middle ear bones that no longer function properly. In a condition called otosclerosis, the stapes becomes frozen to the cochlea and can no longer vibrate up and down. The laser is currently utilized to create a small hole in the footplate of the stapes that allows replacement of the stapes with a new synthetic piston. The advantage of the laser is that it is much less traumatic at making a tiny hole as compared to a drill. Another new advance is the availability of a synthetic bone paste that is pliable yet hardens into new bone. This bone paste can be molded into any shape and after it solidifies it can re-join bones that have become separated.
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