Otosclerosis

Otosclerosis

Function of the Normal Ear

There are three parts to the ear: the external ear, the middle ear, and the inner ear.  Each part plays a role, and each may be affected.  Normally, sound waves pass through the ear canal (external ear) and cause the ear drum to vibrate.  The ear drum (tympanic membrane) separates the external ear from the middle ear.  The middle ear contains three hearing bones (ossicles) and air.  The middle ear space “breathes” through the eustachian tube.  These are the smallest bones in the body.  Vibration of the ear drum causes movement of the hearing bones (the malleus or hammer, incus or anvil, and stapes or stirrup).  The stapes interfaces with the fluid that fills the inner ear (or cochlea), and its movement causes a fluid wave to pass through the inner ear.  This fluid wave causes movement of tiny hair cells within the cochlea.  When those hair cells are displaced they generate an electrical signal that is transmitted by the hearing nerve to the brain where it processed.

Types of Hearing Loss

Since the external and middle ear conduct sound.  If there is a problem with external or middle ear it was cause a conductive hearing loss.  The inner ear creates the electrical signal and transmits it through the nerve.  If there problem is in the inner ear, a sensorineural hearing loss results.  When the problem effects both systems it creates a mixed hearing loss.

Hearing Loss from Otosclerosis

If we were able to examine the bone of your inner ear under a microscope, we would see minute areas of both softening and hardening of the bone.  Over time, this area spreads and hardens.  This process may spread to the stapes, the inner ear, or both.

Stapedial Otosclerosis

The stapes is the area most often affected by otosclerosis.  The stapes if the final link between the middle ear and inner ear.  It rests in an area known as the oval window and is in intimate contact with the fluids of the inner ear.  As the bony change occur near the stapes if interferes with its motion.  This causes a conductive hearing loss.  Hearing tests are required to determine the extent of the hearing loss.  This type of hearing loss is correctable with surgery.

Cochlear Otosclerosis

When the bony changes spread to the inner ear a sensorineural hearing loss may develop as it interferes with the nerve function.  This nerve hearing loss is permanent.  It may be combined with stapedial otosclerosis causing a mixed hearing loss.

Treatment of Otosclerosis

Medical

In some cases, Fluoride may be prescribed in an effort to prevent further hearing loss.  Although, it will not improve hearing.

Hearing Rehabilitation

Hearing aids are often successful in rehabilitating the hearing loss due to otosclerosis.  If you are a suitable candidate for surgery, you are also a suitable candidate for hearing aids.  If you are not a surgical candidate, you may still be a candidate for hearing aids.

Surgical

Stapedectomy (or stapedotomy) is recommended for patient with otosclerosis who are candidates for surgery.  The procedure is typically performed under local anesthesia.  The patient is able to go home the day of surgery.

The Stapes Operation

Stapedotomy is performed through the ear canal under local (or general) anesthesia.  Under the microscope the ear drum is turned forward.  The hearing bones are inspected to ensure that it is the stapes that is fixed and not one of the other hearing bones.  The incus and stapes are separated and a laser is used to remove the top portion of the stapes.  The laser is then used to initiate a hole in the footplate of the stapes.  The footplate is the portion of the stapes that interfaces with the fluid of the inner ear.  A drill is then used to create a precise 0.7-millimeter hole in the footplate.  A stapes prosthesis, known as a piston, is then placed into the hole.  The shaft of the piston measures 0.6-millimeters.  The piston has a wire at the top that is secured to the incus.  The ear drum is returned to its normal position.

The stapes prosthesis moves with the sound waves and transmits those waves to the fluid of the inner ear.  The hearing improvement is usually permanent.  The patient goes home the day of surgery and may return to work 3-7 days following surgery.

The patient will need a ride home following surgery.  Air travel is permissible in 48 hours.

Hearing Improvement Following Stapes Surgery

Hearing may be improved immediately following surgery but may fluctuate for the first 2-3 weeks following surgery.  Maximum hearing is obtained by approximately 4 months.  The degree of hearing improvement depends on how the ear heals.  In over 90% of the patients it heals with significant hearing improvement.  In 2% of the patients there may be an improvement in the conductive hearing loss, but a slight high frequency hearing loss.

In less than 1% of patients there will be a severe to profound nerve hearing loss in the operated ear, to the extent that one may not benefit from a hearing aid in that ear.  There is no way to predict this extremely rare complication.  For this reason the poorer hearing ear is usually selected for surgery.

Risks and Complications of Stapedotomy

Tinnitus

Ringing in the ears, frequently present before surgery, is almost always present temporarily after surgery.  It may persist for one to two months and then decrease as hearing improves.  Should the hearing not improve, or get worse, the tinnitus may persist.

Dizziness

Dizziness is common for a few hours following stapedotomy.  Some unsteadiness is also common during the first few postoperative days.  Dizziness with sudden head motion may persist for several weeks.  On very rare occasions the dizziness is prolonged.

Taste Disturbance and Mouth Dryness

The nerve that supplies taste and sensation to a portion of the tongue is called the chorda tympani.  It runs through the middle ear and may be affected by surgery.  This may cause a taste disturbance and/or dry mouth for a few weeks following surgery.

Loss of Hearing

Further hearing loss develops in 2% of patients due to some complications in the healing process.  In extremely rare cases this hearing loss is severe and may prevent the use of an aid in the operated ear.

Ear Drum Perforation

A perforation (hole) in the ear drum is an uncommon complication.  It occurs in less than 1 percent.  Fortunately, should this happen it usually heals spontaneously.  If it doesn’t, it may require surgical repair.

Weakness of the Face

A very rare complication of stapedotomy is temporary weakness of the face.  This may occur as the result of abnormal swelling of the facial nerve.  It resolves of the course of 4-12 weeks.

Hearing Aid Donation

If your surgery is successful and you regain hearing and no longer need your hearing aid, it would be greatly appreciated if you would donate your hearing aid to the Idaho Ear Clinic.  Donated hearing aids are given to patients who are otherwise unable to afford hearing aids.

General Comments

If you are a suitable candidate for surgery and do not have the stapes operation at this time, it is advisable to have careful hearing tests repeated at least one a year.

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