Anatomy

The middle ear consists of 1) three tiny bones connecting the tympanic membrane to the inner ear, 2) the opening of the Eustachian tube leading down and inward to the back of the throat, 3) an air-filled cavity in which these tiny bones reside, and 4) a number of landmarks on the medial (toward the middle) aspect of the cavity.

The three tiny bones of the middle ear have both Latin and “descriptive” names. The first bone is attached to the tympanic membrane. It is called the malleus, or hammer. The middle bone is termed the incus, or anvil, and the innermost bone (also the smallest bone in the human body) is called the stapes or stirrup. These bones act in unison as a lever to provide a bridge between the energy in the air and the energy that the inner ear will require.

Named after the Middle Age anatomist who discovered it, the Auditory Tube of Eustacius is a passageway for air into the middle ear space. This “Eustachian” tube is normally closed at the back of the throat so that food and liquid do not enter the middle ear space. The tube opens normally during swallowing and yawning, allowing for air pressure equalization between the middle ear space and the external environment.

Damage and Disease

The most common problem in the middle ear occurs in childhood in the form of “otitis media.” This condition, commonly referred to as an ear infection, is sometimes not an infection at all. The general condition results from the inability of the Eustachian tube to properly open and close (to allow air into the middle ear space). This, in turn, is generally the result of swollen tonsils and adenoids in the throat.

As the middle ear space air is absorbed by the lining of the cavity, and no replacement air is available, the lining exudes a clear (serous) fluid which impedes movement of the tympanic membrane and the middle ear bones. This lack of movement causes a mild hearing loss. In children, this condition generally occurs in both ears because both tonsils and adenoids are swollen. It occurs in most children at one time or another and generally recedes or goes away spontaneously. In some cases, the condition does change into an infectious condition which must be correctly diagnosed and medically treated.

There are other diseases which impair the middle ear, among them perforation of the tympanic membrane – sometimes secondary to chronic otitis media, sometimes the result of physical trauma to the head (blows to the ear, rapid changes in air pressure, and the like), and occasionally, skin growths in the middle ear space.

Function

The middle ear converts acoustic energy, received by the tympanic membrane, into mechanical energy, which stimulates the structures of the inner ear. Since middle ear structures act as an energy transducer, they are very important in a person’s ability to hear very quiet sounds. If one were to lose function of the middle ear through disease or other injury, the ear would become approximately 1000 times less sensitive (30 decibels of hearing loss).

Treatments

There are many treatments for otitis media, including medication (antibiotics and decongestants) and surgeries. In times past, a tonsillectomy would be performed to remove the obstruction to the Eustachian tube. Research has demonstrated that, in many situations, removing the tonsils is not necessary to treat serous otitis media effectively. If the tympanic membrane is perforated, medication will seldom “heal” this condition, and surgery will provide the best means of resolution. The extent of the surgical treatment will depend upon the nature of the disease and the length of time the ear problem has existed. As with most health problems, early identification of the disease or problem (and subsequent early intervention) provides the highest probability of successful treatment.