Otosclerosis occurs when normal bone is replaced with spongy, vascular bone that may harden.  Occurs most often anterior to the oval window.  The addition of new bone around the stapes causes the stapes to become immobile and unable to transmit sound to the cochlea.  The result is a conductive hearing loss.


Prevalence:
    - 1 in every 5 to 10 white women
    - 1 in 100 black people are affected
    - Age of onset is usually 20 - 30
    - Most common cause of serious hearing loss among young adults
    - 1/10 of cases actually develop disease.

Causes:
    - An autosomal dominant gene with variable penetrance
    - Genetic, not congenital
    - Not sex-linked (Although, may be aggravated and activated by certain
                            metabolic and chemical changes that accompany pregnancy
                            and menstruation)

Symptoms:
    - 70 % report tinnitus
    - 25 % report vertigo or imbalance
    - Willis paracusia (patient hears better in noise)

Clinical signs:
    - Conductive hearing loss
    - Pinkish or rosy tint on TM (Schwartz sign) in 10 % o cases
    - Air-bone gap at most frequencies with exception of 2 kHz (Carhart's Notch)
    - 85 % of cases are bilateral
    - Decreased amplitude and a flattened sloped tympanogram
    - Excellent speech discrimination at adequate levels
    - absent acoustic reflexes

Treatments:
    - Medical / Nonsurgical
  1. sodium fluoride (thought to restrict bone growth by hardening it)
  2. Amplification

    - Surgical
  1. Fenestration (a new window drilled in to lateral semicircular canal at the level
                              of the promontory and covered with a membrane.  New window
                              exposed to outer air.  Patient retains a 25 dB conductive loss due
                              to the loss of the transformer action of the middle ear.  Rarely
                              performed today).
  2. Stapedolysis or Stapes Mobilization (eardrum is raised.  A hook-like
                              instrument is attached to the crus of the stapes and jerked,
                              freeing the footplate from the growth.  Usually only a temporary
                              solution.  New bone would eventually grow back.  Operation is
                              rarely performed today).
  3. Stapedectomy (removal of stapes, replacing with a prosthesis.  Point of
                              prosthesis is inserted into the oval window and packed with a
                              material that holds the device in place while normal tissue
                              growth occurs.  It is 97-99% effective.  Hundreds done daily.
 

(Information taken from David C., Joey H., and an unknown author from Ball State UniversityAu.D. program)