What is otosclerosis?
Otosclerosis may be a term derived from oto, meaning “of the ear,” and sclerosis, meaning “abnormal hardening of body tissue.” The condition is caused by abnormal bone remodeling within the tympanic cavity. Bone remodeling may be a lifelong process during which bone tissue renews itself by replacing old tissue with new. In otosclerosis, abnormal remodeling disrupts the power of sound to travel from the center ear to the internal ear.
How can we hear?
Healthy hearing relies on a series of events that change sound waves within the air into electrochemical signals within the ear. The acoustic nerve then carries these signals to the brain.
First, sound waves enter the external ear and travel through a narrow passageway called the auditory meatus , which results in the eardrum.
The incoming sound waves make the eardrum vibrate, and therefore the vibrations visit three tiny bones within the tympanic cavity called the malleus, incus, and stapes—the Latin names for hammer, anvil, and stirrup.
The middle-ear bones amplify the sound vibrations and send them to the cochlea, a fluid-filled structure shaped sort of a snail, within the internal ear . The upper and lower parts of the cochlea are separated by an elastic, “basilar” membrane that is the bottom , or ground floor, upon which key hearing structures sit.
Incoming sound vibrations cause the fluid inside the cochlea to ripple, and a wave forms along the membrane . Hair cells that sit on top of the membrane “ride” this wave and move up and down with it.
The bristly structures of the hair cells then raise against an overlying membrane, which causes the bristles to tilt to at least one side and open pore-like channels. Certain chemicals then rush in, creating an electrical signal that's carried by the acoustic nerve to the brain. The top result's a recognizable sound.
Hair cells near the bottom of the cochlea detect higher-pitched sounds, like a telephone ringing. Those nearer the center detect lower-pitched sounds, like an outsized dog barking.
What causes otosclerosis?
Otosclerosis is most frequently caused when one among the bones within the tympanic cavity, the stapes, becomes stuck in situ . When this bone is unable to vibrate, sound is unable to travel through the ear and hearing becomes impaired.
Why this happens remains unclear, but scientists think it might be associated with a previous measles infection, stress fractures to the bony tissue surrounding the internal ear , or immune disorders. Otosclerosis also tends to run in families.
It may even have to try to with the interaction among three different immune-system cells referred to as cytokines. Researchers believe that the right balance of those three substances is important for healthy bone remodeling which an imbalance in their levels could cause the type of abnormal remodeling that happens in otosclerosis.
What are the symptoms of otosclerosis?
Hearing loss, the foremost frequently reported symptom of otosclerosis, usually starts in one ear then moves to the opposite . This loss may appear very gradually. many of us with otosclerosis first notice that they're unable to listen to low-pitched sounds or can’t hear a whisper. Some people can also experience dizziness, balance problems, or tinnitus. Tinnitus may be a ringing, roaring, buzzing, or hissing within the ears or head that sometimes occurs with deafness .
How is otosclerosis diagnosed?
Otosclerosis is diagnosed by health care providers who concentrate on hearing. These include an otolaryngologist (commonly called an ENT, because they're doctors who concentrate on diseases of the ears, nose, throat, and neck), an otologist (a doctor who focuses on diseases of the ears), or an audiologist (a health care professional trained to spot , measure, and treat hearing disorders). the primary step during a diagnosis is to rule out other diseases or health problems which will cause an equivalent symptoms as otosclerosis. Next steps include hearing tests that measure hearing sensitivity (audiogram) and middle-ear sound conduction (tympanogram). Sometimes, imaging tests—such as a CT scan—are also wont to diagnose otosclerosis.
How is otosclerosis treated?
Currently, there's no effective drug treatment for otosclerosis, although there's hope that continued bone-remodeling research could identify potential new therapies. Mild otosclerosis are often treated with a hearing aid that amplifies sound, but surgery is usually required. during a procedure referred to as a stapedectomy, a surgeon inserts a prosthesis into the center ear to bypass the abnormal bone and permit sound waves to visit the internal ear and restore hearing.
It is important to debate any surgery with an ear doctor to clarify potential risks and limitations of the operation. for instance , some deafness may persist after stapedectomy, and in rare cases, surgery can actually worsen deafness .
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