First, in order to understand possible problems of the middle ear and eustachian tube, a brief review of ear anatomy & physiology is in order.
MECHANISM OF HEARING
The ear is comprised of three portions: an outer ear (external), a middle ear and inner ear. The outer (external) ear consists of an auricle and ear canal. These structures gather the sound and direct it toward the ear drum (tympanic membrane).
The middle ear chamber lies between the external and inner ear. This chamber is connected to the back of the throat (pharynx) by the eustachian tube which serves as a pressure equalizing valve. The middle ear consists of an eardrum and three small ear bones (ossicles): malleus (hammer), incus (anvil) and stapes (stirrup). These structures transmit sound vibrations to the inner ear. A disturbance of the eustachian tube, eardrum or the ear bones may result in a conductive hearing impairment. This type of impairment is usually corrected medically or surgically.
FUNCTION OF THE EUSTACHIAN TUBE
The eustachian tube is a narrow channel which connects the middle ear with the nasopharynx (the upper throat area just above the palate, in back of the nose). The Eustachian tube is approximately 1 1/2 inches in length. The narrowest portion is that area near the middle ear space.
The eustachian tube functions as a pressure equalizing valve of the middle ear, which is normally filled with air. Under normal circumstances the eustachian tube opens for a fraction of a second in response to swallowing or yawning. In so doing it allows air into the middle ear to replace air that has been absorbed by the middle ear lining (mucous membrane) or to equalize pressure changes occurring with altitude changes. Anything that interferes with this periodic opening and closing of the eustachian tube may result in a hearing impairment or other ear symptoms.
Obstruction or blockage of the eustachian tube results in a negative middle ear pressure, with restraction (sucking in) of the eardrum (tympanic membrane). In an adult this is usually accompanied by some discomfort, such as a fullness or pressure feeling, and may result in a mild hearing impairment and head noise (tinnitus). In children there may be no symptoms. If the obstruction is prolonged, the fluid may be sucked in from the mucous membrane in the middle ear creating a condition called serous otitis media (fluid in the middle ear). This occurs frequently in children in connection with an upper respiratory infection or allergies and accounts for the hearing impairment associated with this condition.
On occasion just the opposite from blockage occurs; the tube remains open for a prolonged period. This is called abnormal patency of the eustachian tube (patalous eustachian tube). This is less common than serous otitis media and occurs primarily in adults. Because the tube is constantly open the patient may hear himself breathe and hears his voice reverberate in the affected ear. Fullness and a blocked feeling are not uncommon sensations experienced by the patient. Abnormal patency of the eustachian tube is annoying but does not produce a hearing impairment.
EUSTACHIAN TUBE PROBLEMS RELATED TO FLYING
Individuals with a eustachian tube problem may experience difficulty equalizing middle ear pressure when flying. When an aircraft ascends, the atmospheric pressure decreases, resulting in a relative increase in the middle ear air pressure. When the aircraft descends, just the opposite occurs; atmospheric pressure increases in the cabin of the aircraft and there is a relative decrease in the middle ear pressure. Either situation may result in discomfort in the ear due to abnormal middle ear pressure compared to the cabin pressure, if the eustachian tube is not functioning properly. Usually, this discomfort is experienced upon descent of the aircraft.
To avoid middle ear problems associated with flying you should not fly if you have an acute upper respiratory problem such as a common cold, allergy attack or sinus nfection. Should you have such a problem and must fly, or should have a chronic eustachian tube problem, consult with your Physician and he/she may recommend one or more of the following:
SEROUS OTITIS MEDIA
Serous otitis media is a term which is used to describe a collection of fluid in the middle ear. This may be a recent onset (acute) or may be long standing (chronic).
Serous otitis media is the most common cause of hearing loss in children. Fortunately, the hearing loss associated with this condition usually is not permanent. However, serous otitis media may be present without recurrent ear infections and a mild hearing loss may be the only sign of its presence. Prompt Audiological identification of the hearing loss and Medical intervention, usually restore hearing to normal or near normal levels.
Serous Otitis Media is quite common in young children. Although the hearing involvement that ocurrs as a consequence is rarely severe, left over a long period of time, has been known to cause or exacerbate speech and language delays. Again prompt identification and intervention are advised.
Acute serous otitis media is usually the result of blockage of the eustachian tube from an upper respiratory infection or an attack of nasal allergy. In the presence of bacteria this fluid may become infected leading to an acute suppurative otitis media (infected or abscessed middle ear).This chronic condition is usually associated with a hearing impairment. There may be recurrent ear pain, especially when the individual catches a cold.
Serous otitis may persist for many years without producing any permanent damage to the middle ear mechanism. Presence of fluid in the middle ear, however, makes it very susceptible to recurrent acute infections. These recurrent infections may result in middle ear damage.
CAUSE OF SEROUS OTITIS MEDIA
Serous otitis media may result from any condition that interferes with the periodic opening and closing of the eustachian tube. The causes may be congenital (present at birth), may be due to infection or allergy, or may be due to mechanical blockage of the tube.
The Immature Eustachian Tube
The size and shape of the eustachian tube is different in children than in adults. This accounts for the fact that serous otitis media is more common in very young children. Some children inherit a small eustachian tube from their parents; this accounts in part for the familial tendency to middle ear infection. As the child matures, the eustachian tube usually assumes a more adult shape
The lining membrane (mucous membrane) of the middle ear and eustachian tube is connected with, and is the same as, the membrane of the nose, sinuses and throat. Infection of these areas results in the mucous membrane swelling, which in turn may result in eustachian tube obstruction.
Allergic reaction in the nose and throat result in swelling of the mucous membranes and this swelling may also affect the eustachian tube. This reaction may be acute or chronic.
ACUTE SEROUS OTITIS MEDIA
Treatment of acute serous otitis media is medical, and is directed towards treatment of the upper respiratory infection or allergy attacks. This may include antibiotics, antihistamines (anti-allergy drugs), decongestants (drugs to decrease mucous membrane swelling) and nasal sprays.
ACUTE SUPPURATIVE OTITIS MEDIA
In the presence of an upper respiratory infection, such as a cold, tonsillitis, or pharyngitis, fluid in the middle ear may become infected. This results in what is commonly called an abscessed ear or an infected middle ear.
This infected fluid (pus) in the middle ear may cause severe pain. If the audiological and medical evaluations reveal there is considerable ear pressure, a myringotomy (incision of the eardrum membrane) may be necessary to relieve the pressue, drainage, and the pain. In many instances antibiotic treatment will suffice. The pressure equalization tube inserted usually stays in and open for 4-6 months and then is naturally pushed out be healing processes in the ear.
CHRONIC SEROUS OTITIS MEDIA
Treatment of chronic serous otitis media may either be medical or surgical.
As the acute upper respiratory infection subsides, it may leave the patient with a persistent eustachian tube blockage. Antibiotic treatment may be indicated.
Allergy is often a major factor in the development or persistence of serous otitis media. Mild cases can be treated with antihistaminic drugs. Again, the insertion of a ventilation tube is indicated when the ears are not responsive to pharmacological treatment.
The ventilation tube temporarily takes the place of the eustachian tube in equalizing middle ear pressure. Usually the chonic condition resolves while the tube is in place, not requiring the re-insertion of an additional tube.
In adults, a myringotomy and insertion of a ventilation tube is usually performed in the office under local anesthesia, with the use of a topical solution placed on top of the tympanic membrane. In children, general anesthesia is required.
When a ventilation tube is in place, a patient may carry on normal activities with the exception that no water must enter the ear canal. Often this can be prevented with vaseline on a cotton ball or a silicone ear plug. In addition, a custom made earmold, made by the Audiologist, will often prevent water from entering the ear canal.
The Role of the Audiologist in the Diagnosis of Eustachian Tube and Middle Ear Disorders.
Although the discomfort which often accompanies middle ear and Eustachian Tube maladies often will bring an adult straight to a Physician, sometimes, especially with children, ther is no discomfort. With them, often, the only way to know of a middle ear or Eustachian Tube discorder is from a louder T.V. Or a report home from school that there are more "whats" or "huhs" in the classroom, as a consequence from the ensuing hearing involvement. Hearing screening in the schools, Pediatricians' offices, or audiologic follow-up by the Audiologist, may be the first line of identification of these disorders.
Even before a hearing loss presents itself, tympanometry may be the most sensitive diagnostic test for middle ear and Eustachian Tube disorders. With tympanometry (see Services section for more details) the Audiologist inserts a small probe to the outside of the ear canal for 5 seconds. The probe "reads" how much sound energy is transferred in to the inner ear. If too much sound energy is reflected back to the probe, fluid in the middle ear cavity, due to one of the above reasons, is suspected. Also, tymanometry can read whether the ear drum is drawn in due to negative middle ear pressure, an often times precursor to middle ear fluid.
Even after ventilation tubes (P.E. Tubes) are inserted, hearing tests are important to monitor and substantiate the improved hearing. Moreover, the tympanometry can verify that the P.E. Tubes are still functional.