Our remarkable ability to hear is the result of tiny and delicate instruments within the ears working in conjunction with larger parts. The precision with which these parts work together is an amazing feat that can sometimes go awry. When any one of these complex parts becomes damaged hearing loss can happen. Sometimes the cause of hearing loss is something that could have been avoided, like noise, and sometimes it's something no one could have foreseen, like the mysterious bone growth associated with otosclerosis.
In order to understand how otosclerosis happens, it's best to know how the middle ear works.
The middle ear consists of the eardrum (tympanic membrane) and three small bones, hammer (malleus), anvil (incus), and the stirrup (stapes). Collectively these small bones are known as the ossicles. Sound waves funneled from the outer ear strike the eardrum causing it to vibrate, amplifying the sound and setting into motion the three flexible bones of the ossicles. The amplified sound is then transformed into energy delivered to the inner ear as fluid vibrations.
How Otosclerosis Happens
Although the cause is mysterious, otosclerosis happens because there is abnormal bone growth around the ossicles (three tiny bones of the middle ear).
The ossicles bones need to remain flexible for vibrations to be transmitted into sounds, but the abnormal growth that results from otosclerosis fixates one or more of these bones impeding hearing. The result is typically a decline in conductive hearing—as the passage in the middle and outer ear becomes immune to sound waves. Rarely, otosclerosis can result in sensorineural hearing loss, meaning it’s not the middle ear or even outer ear damaged, but the delicate hair cells of the inner ear. Decline in hearing in all cases is gradual and is usually noticed in the third decade or later in life.
Causes of Otosclerosis
The exact cause of the otosclerosis remains a mystery, but there are some factors thought to contribute to its likelihood.
Hereditary—otosclerosis can be inherited and is 25% more likely if one parent has it and 50% more likely if two parents have it.
Pregnancy—otosclerosis is more common in pregnant women or women who’ve had multiple pregnancies.
Viral—research suggests that there is a link between the emergence of this condition and exposure to certain viruses like measles. It is thought that the condition may lay dormant within a person until it is instigated by exposure.
Symptoms of Otosclerosis
Tinnitus—a buzzing, clicking, or whining sound within the ear when there is no noise present.
Hearing loss—the most common sign of otosclerosis is hearing loss. A deficit in ability to hear low pitched sounds, whispers, women’s and children’s voices is typically a first stage in this hearing loss.
Balance—loss of balance that may include nausea and feelings of vertigo is also a symptom of this condition.
Although the exact cause of otosclerosis is a mystery, there are some things that are known. For example, otosclerosis is usually bilateral, meaning it occurs in both ears. It is also more common in women than men, and afflicts Caucasians and Asians more than African Americans. On Wednesday People Hearing Better will look at some of the ways an audiologist can treat this condition and expected recovery time after treatment. If you suspect you have hearing loss, don't wait, make an appointment with your audiologist to uncover the cause and find the best treatment.