Otosclerosis is a condition that occurs only in the temporal bone and middle ear.  Otosclerosis refers to the condition of new bone formation usually around the stapes.  The cause of this new bone growth is not always clear.  Perhaps fifty percent of patients have a family history of otosclerosis.  The remainder of patients do not have a family history and are thus called "sporadic" cases.  Otosclerosis occurs in both ears in the majority of patients (maybe as high as 70%).  

A relatively new theory for the development of otosclerosis involves measles virus.  Researchers have isolated measles virus DNA from otosclerotic bone.  This viral cause of otosclerosis might explain the sporadic cases.  Additionally, it might also explain the apparent decrease in incidence of otosclerosis, since a measles vaccine has been present for almost 40 years.

The most common symptom of otosclerosis is a mild to moderate conductive hearing loss.  [To learn more about types of Hearing Loss, please follow this link.]   This conductive hearing loss usually starts in the third decade of life (your 20's), but the onset of otosclerosis might be found in childhood or in later life.  An unusual characteristic of the hearing loss in otosclerosis is that it can worsen significantly during a woman's pregnancy. 

The most common location for this new bone formation is around the footplate of the stapes.  The stapes is the smallest bone in the body.  It is the third bone in the chain of bones that connect the eardrum to the inner ear.  The footplate of the stapes fills the oval window and is held in place by an annular ligament.  

Sound waves travel through the ear canal to the eardrum.  Vibration of the eardrum moves the small bones (ossicles) of the middle ear.  The vibration of the stapes changes the sound wave into a fluid wave in the cochlea.  Without adequate vibration of the stapes, sound is not conducted well into the cochlea and a conductive hearing loss is found.

Otosclerosis can occur around the stapes footplate, the oval window, the round window, the facial nerve, and the cochlea.   The most common location is on the anterior footplate.  However, the entire annulus or even the entire footplate can be covered by the otosclerotic bone.  

Patients with otosclerosis might also have a low pitched ringing sound (tinnitus).  Sensorineural hearing loss can occur with otosclerosis that involves the cochlea or the cochlear nerve.  Vertigo is not typically caused by otosclerosis; however, some conditions that cause vertigo (such as Meniere's disease) can occur in patients with otosclerosis as well.

The diagnosis of otosclerosis requires a careful history and physical examination by your physician.  Other causes of hearing loss, such as otitis media, eardrum perforation, cholesteatoma, etc are eliminated.  An audiogram is performed to document the type and degree of hearing loss that is present.

Treatment for otosclerosis depends on several factors.  The chief determinant is the degree of hearing loss.  Patients with mild conductive hearing loss might simply be observed with periodic audiometry.  Patients with more significant hearing loss can chose either hearing aids or surgery (stapedectomy) to help overcome the hearing loss.