Using the Otoscope

Acute Otitis Media (AOM) is a condition diagnosed and treated by primary care physicians as well as specialists. Accurate diagnosis and a proper understanding of the underlying pathophysiology are crucial for the optimal management of this disease. The following otoscopic images of the tympanic membrane show a progression through the stages of a typical episode of otitis media. These should help promote an integrated understanding of the OM disease process.

APPEARANCE OF TYMPANIC MEMBRANE
WITH ACUTE OTITIS MEDIA
Normal Membrane	Opaque with Inflammation	Bulging Membrane
Chronic Inflammation	Late, Severe OM	Resolving Infection

The Normal Tympanic Membrane (shown above, left) is a semi-transparent cone shaped structure, approximately 1 cm in diameter located at the end of the ear canal. Size ranges from 10 mm at birth to 24 mm in adulthood. The membrane is "tilted", with the anterior edge being more medial than the posterior edge. The simplest way to detect an active infection in the middle ear is to look in the ear with an otoscope, a light instrument that allows the outer ear and the eardrum to be examined. The "cone of light" is a bright area extending from the center of the membrane, the umbo, forward. It is seen as light reflected back from the otoscope at a 900 angle from the light source. Inflammation of the eardrum indicates an infection.

Otitis Media: A Disease Presentation

Otitis media is an inflammation of the middle ear and it can be classified as acute otitis media (AOM), or as otitis media with effusion (OME) which is a chronic disease. Otitis media can affect people from any age group, but most commonly affects infants and young children and is considered one of the most common diseases of childhood. AOM is one of the most commonly diagnosed diseases in the US with over thirty million Americans are affected by this condition each year. Eighty-five to ninety percent of children will have at least one episode of acute otitis media, and twenty-five percent will have more than six. Clearly this disease has a major impact in the U.S. This includes social and medical implications, as well as the economic burden of missed work and antibiotic prescriptions.

Signs & Symptoms

Acute Otitis Media (AOM)

Symptoms include otalgia (ear pain), a reduction in hearing, fever, unsteadiness, and occasionally otorrhea (liquid draining from the ear) if the tympanic membrane bursts. Signs include an immobile tympanic membrane, which can be dull, opaque, red, bulging, or even show pus seeping through it: any appearance outside the norm of a tympanic membrane that is mobile when tested by a light puff of air through a pneumatic otoscope and pearly gray to pink in color, shiny, translucent and concave (see below, left). There may be a demonstrable conductive hearing loss that can be tested using a tuning fork in diagnosing a patient with otalgia. When the tuning fork is placed at the center of the skull, it will normally be heard as a midline sound. With a conductive hearing loss, the sound will appear to be on the side of the bad ear. By contrast, with sensorineural loss, the sound will be heard with the better ear.

Otitis media with Effusion (OME)

Symptoms include hearing loss, tinnitus, and unsteady gait. OME can be entirely asymptomatic. Effusions may persist for several weeks after AOM with 60% of patients clear of effusion at 2 weeks. Signs include conductive hearing loss, and a tympanic membrane either retracted or bulging, and possibly showing an air-fluid level that indicates fluid accumulation.

Risk Factors for Both Recurrent Acute and Chronic Otitis Media

Day care (the risk increases with an increasing number of children, up to about 10 or 20)
Exposure to second hand smoke
Lack of breast-feeding
Sleeping prone
Allergies
Immunosuppression

Physiology and Testing Methods

The three known main functions of the eustachian tube are drainage, pressure equilibration and protection. Drainage, or clearance of middle ear secretions by muscular or mucociliary function, is documented in only a few studies, but pressure equilibration and protection, are accomplished by active and passive functions of the tube and have been more extensively studied.

Obstruction (opening failure) and abnormal patency (closing failure) are two types of eustachian tube dysfunction. Both of these conditions can predispose a patient to otitis media. Tubal obstruction may be either functional or mechanical. Functional obstruction can be measured by the active function tests, defined as the ability to equilibrate positive and negative pressures in the middle ear by tubal muscular opening during swallowing. Good active function is classified as the ability to equilibrate both positive and negative middle ear pressures, and poor active function is the inability to equilibrate negative pressures.

Mechanical obstruction may be the result of extrinsic factors, such as a tumor or an adenoid, or of intrinsic factors, including mucosal swelling and lack of mucosal surfactants. Abnormal patency and mechanical obstruction can be measured by passive function tests.

There are several ways to check for middle ear fluid. One is to use a special pneumatic otoscope where a puff of air is blown onto the eardrum to test eardrum movement. An eardrum with fluid behind it does not move as well as an eardrum with air behind it. A useful test of middle ear function is called tympanometry. This test requires insertion of a small soft plug into the opening of the ear canal. The plug contains a speaker, a microphone, and a device that is able to change the air pressure in the ear canal, allowing for several measures of the middle ear. The child feels air pressure changes in the ear or hears a few brief tones. While this test provides information on the condition of the middle ear, it does not determine how well the patient hears. A physician may suggest a hearing test for a child who has frequent ear infections to determine the extent of hearing loss. The hearing test is usually performed by an audiologist, a person who is specially trained to measure hearing.

Microbiology and Laboratory Testing

The most common pathogens are Streptococcus pneumoniae, nontypeable Haemophilus influenzae, Moraxella catarrhalis, and viruses such as rhinovirus and adenovirus. The key test for establishing an accurate diagnosis for otitis media is pneumatoscopy. since an immobile tympanic membrane correlates best with presence of an effusion.

For a single acute infection, no further testing is needed. If the effusion persists and there is evidence of hearing loss, most frequently self-reported or reported by the parent, the patient's hearing should be tested formally. In patients diagnosed with chronic otitis media, hearing should always be tested.

Treatment

This is somewhat of an area of debate at the present time in medical history (2003). Antibiotic treatment is thought to resolve symptoms more quickly in only 1 of 7 patients, so that their use is contraindicated. In addition, antibiotic overuse in the past has allowed for the development of drug-resistant strains of common OM-causing bacteria.

However, the use of antibacterials is associated with a lower rate of complication, which can include acute mastoiditis, intracranial spread of infection, and tympanic membrane perforation.

For acute otitis media, treatment consists of antibiotics and acetaminophen. First line treatment antibiotic is still Amoxicillin in an appropriate dose. If resolution does not start within 48 to 72 hours, a change in antibiotic is probably needed. Second line antibiotics include amoxicillin-clavulanic acid, cephalosporins such as cefaclor, cefixime, cefuroxime axetil, cefpodoxime, macrolides such as azithromycin and clarithromycin, and sulfa drugs such as trimethaprim-sulfamethoxazole and erythromycin-sulfisoxazole.

**VENTILLATION TUBE PLACEMENT**
For chronic otitis media, ventilation tubes may be indicated. The formal criteria for the surgery (termed myringotomy with insertion of tympanostomy tubes) include three or more episodes of OM in a 6 month period or 4 episodes during a 1 year period) and bilateral OME which has been unresponsive to non-surgical therapy for three months or greater with an associated hearing loss.

A Case of Otitis Media

Opaque with Inflammation

Bulging Membrane

Late, Severe OM

The Inflammed Tympanic Membrane in a 6-year-old patient who has had an upper respiratory tract infection (URI) for 4 days is shown above (left picture). The patient was beginning to recover, but over the past 24 hours he developed otalgia, but had no fever. Redness and outward bulging with surface blood vessels of the TM generally dilated. Inflammation of the distal ear canal may or may not be present (it is visible here).

The patient has now had 48 hours of ear pain and has developed fever. The otalgia is worsening and there is now more redness, swelling, and inflammation of the tympannic membrane, which is beginning to bulge outward (Above, center picture).

After 72 hours the patient now has severe otalgia and the fever persists. The membrane is now severely swollen from the inflammation and the landmarks can no longer be seen. There is obvious outward bulging of the and if the patient is not treated soon, the tympanic membrane might rupture spontaneously, releasing the pus under pressure (above, right picture). The patient was treated with a second generation cephalosporin antibiotic early, because he had failed treatment with amoxicillin during prior infections. A second generation cephalosporin should have good coverage for the three main bacterial pathogens in AOM.


Stained Middle Ear Effusion: PMNs are prominent.	Resolved acute otitis media with crust, left ear.

A sample of middle ear effusion exudate was collected by needle aspiration, examined microscopically (Left, Above), and tested for sensitivity to the antibiotic of choice. After 5 days of treatment, the patient's inflammation resolved significantly and there was no longer any pain. The patient still complains of "fullness in the ears" and has a mild conductive hearing loss. There is still a visible air-pus level inferiorly. If draining continues, the episode should completely resolve. If there is persistent eustachian tube dysfunction, the fluid will not drain and the patient's infection could become chronic. This patient's infection resolved completely (crust over tympanic membrane, Right, Above). Want More Information about Otitis Media? Go to the Following Ear, Nose and Throat Specialty Website.

References

Waitzman, A, Dept of Otolaryngology, Wayne State University and Hawke, M, Dept of Otolaryngology and Pathology, University of Toronto; http://www.silentpartners.org/ENT/patients/earache.htm

AMERICAN ACADEMY OF PEDIATRICS Policy Statement, Section on Otolaryngology and Bronchoesophagology. Follow-up Management of Children With Tympanostomy Tubes (2002) Pediatrics 109: 328-329.

Bluestone CD. Otitis media: to treat or not to treat? (1998) Consultant: 1421-33.

Golz A, Netzer A, Joachims HZ, Westerman ST, Gilbert LM. Ventilation tubes and persisting tympanic membrane perforations. (1999) Otolaryngol Head Neck Surg 120: 524-7.

Page last updated October 24, 2004; Mary T. Johnson, Ph.D.