Glossary

External auditory canal

This is the outer ear canal. It is the pathway from the outside world down to the eardrum. Infections of the external auditory canal are referred to as otitis externa, or swimmer?s ear.

Tympanic membrane

The tympanic membrane is commonly referred to as the eardrum. It measures a little less than 1 cm in diameter. The tympanic membrane has 3 layers: a thin layer of skin on the outside, a mucous membrane on the inside and a thin elastic layer in the middle. A healthy tympanic membrane is clear and the middle ear can be seen through it.

Ossicles

These are the chain of bones in the middle ear that connect the ear drum to the inner ear. They consist of the malleus, the incus and the stapes.

Malleus

The malleus is the bone embedded in the eardrum. It is the first bone in the chain. It collects sound from the eardrum and transmits it to the other bones in the chain.

Incus

The incus is a small bone which connects the malleus to the stapes. The area where the incus joins the stapes has a poor blood supply and is prone to damage. This damage is often referred to as necrosis.

Stapes

The stapes is the last bone in the chain. It looks like a stirrup with a top arch and a bottom plate called the footplate. It connects to the fluids of the inner ear. It acts like a piston in a cylinder. When sound moves the eardrum in and out, the movement goes through the chain of middle ear bones to the stapes which moves the fluids of the inner ear. The movement of the inner ear fluid is then transmitted to the brain. In some individuals a disease called otosclerosis locks the stapes to the bone surrounding it. If a surgeon removes the stapes it is called a stapedectomy. The surgeon may alternately make an opening in the foot plate of the stapes and that is called a stapedotomy.

Eustachian tube

The eustachian tube connects the middle ear to an area directly behind the nose. This allows fluid to drain out of the middle ear and air to get into the middle ear. Normally when we chew, swallow, or yawn, the eustachian tube will open and then close. If the tube stays open abnormally long, it is referred to as a patulous eustachian tube. If the tube will not open properly, it is often referred to as Eustachian tube dysfunction. Eustachian tube dysfunction is thought to occur as a result of numerous abnormalities. It causes the collection of fluid in the middle ear and makes one prone to infection. Without the air from the eustachian tube, all of the air in the middle ear reabsorbs into the blood and this retracts the tympanic membrane resulting in abnormal middle ear function. Some diseases are known to affect the eustachian tube. Certain congenital diseases of the middle portion of the face can cause abnormal eustachian tube function. These include cleft palate and Downs syndrome. Another disorder which can affect the eustachian tube is smoking. Tobacco smoke will paralyze the normal clearance of fluid through the eustachian tube. Some disorders of eustachian tube dysfunction are not clearly understood.

Mastoid

At birth there are a few air cells associated with the bones directly behind the eardrum. Over the next two years, most individuals develop a group of cells that are normally filled with air. As a person grows, the cells get bigger and continue to fill with air. An infection in this area is referred to as mastoiditis. If a surgeon removes a segment of this bone, it is called a mastoidectomy. This is often necessary to remove infection or cholesteatoma.

Conductive hearing loss

Conductive hearing loss occurs when sound waves moving through the air cannot reach the fluid in the inner ear. The sound waves must go from the outside through the external auditory canal to the tympanic membrane to the middle ear bones and finally to the inner ear. This blockage can occur in the external auditory canal from ear wax or foreign objects. The tympanic membrane may not move because of fluid behind it or a mass behind the eardrum. The chain of ear bones connecting the ear drum to the middle ear may be disconnected or fixed in place so they cannot move.

Sensorineural hearing loss

Sensorineural hearing loss is a problem either with the inner ear or the nerve going to the inner ear. The hearing part of the inner ear contains hair cells and changes mechanical wave motion into an electrical signal. The ability to detect sound depends on healthy hair cells. The neural part is the nerve that connects the hair cells in the inner ear to the brain. Neural loss reduces the ability to understand the sounds that are coming into the brain. Many things can cause sensorineural loss including aging, medications and drugs, prolonged or very loud noise exposure, tumors and problems with the brain itself. Some children are also born with a hearing loss.

Atelectasis

Atelectasis means collapse. When the eardrum collapses into the middle ear and loses its normal elasticity, the eardrum is atelectatic. In some cases, atelectasis can be a warning for the development of more serious disorders. It is due to eustachian tube dysfunction.

Cholesteatoma

Cholesteatoma is "skin in the wrong place." The skin usually comes from the tympanic membrane. It is often due to eustachian tube dysfunction. One of the leading theories is that when the eardrum is atelectatic, the skin of the eardrum becomes adherent to bone that is underneath the eardrum. This creates irregularities which are sometimes referred to as "pockets". The pockets then collect the dead skin debris and become infected. This causes a skin cyst and the sac of dead skin begins to behave like a tumor. It occupies space and does destroys the surrounding bone. It will result in irreversible damage to the bone and any other structures around the cholesteatoma. This can include damage to the middle ear bones, inner ear, facial nerve, balance mechanism, and brain.

Otosclerosis

Otosclerosis is primarily a hard irregular bony growth that occurs between the inner ear and the stapes footplate. It develops in part because of a genetic predisposition so there may be a family history of hearing loss. However, not everyone who has the genetic predisposition will develop hearing loss. Otosclerosis appears irregularly over several generations and tends to occur more frequently in some families. Women are more prone to this disorder than men, particularly during pregnancy. Fluoride helps with preventing progression of the disease, but taking fluoride supplements has not been proven to be helpful. Many communities have fluoride added to the water so there is already a supplement.