Otitis Externa and Otitis Media in Cats
Otitis externa is a chronic inflammation of a cat's external ear canal. Otitis media, meanwhile, is an inflammation of the cat's middle ear. Both of these terms are used to describe clinical symptoms and are not diseases in themselves.
Otitis externa often results when a change in the normal environment of the ear canal causes the glands lining the canal to enlarge and produce excessive wax. Gradually, the outer skin (epidermis) and the inner skin (dermis) produce excessive fibrous tissue (fibrosis) and the canal becomes narrowed. It is normally a secondary symptom of another underlying disease, such as an infection. Otitis externa causes pain, itching, and redness, and when the condition is chronic, it often results in a ruptured ear drum (tympanum) and otitis media.
Otitis media typically occurs as an extension of otitis externa, causing a ruptured membrane (tympanum) that separates the external ear and the middle ear.
The two conditions described in this medical article affect both dogs and cats. If you would like to learn more about how they affect dogs please visit this page in the PetMD health library.
Symptoms and Types
The most common symptoms of otitis externa and otitis media are pain, head shaking, scratching at the external ear flaps, and bad odor. In a physical examination by a veterinarian, a cat with the condition may exhibit redness and swelling of the external ear canal, scaling skin or obstruction of the ear canal. Signs such as tilting the head, anorexia, uncoordination, and occasional vomiting may indicate the development of otitis media, or otitis interna, if the infection and inflammation spreads to the inner ear.
Otitis externa and otitis media can be caused by a variety of things. The primary causes are parasites, food allergies, drug reactions, foreign bodies (e.g., plant awns), accumulation of hair, dead skin buildup (keratinization), and autoimmune diseases.
Other factors that may contribute to the onset of the inflammatory conditions include bacterial infections, mixed infections caused by bacteria and fungal species, and progressive changes in the environment of the outer ear canal. Excessive moisture caused by swimming, or overzealous, abrasive, and improper ear cleaning may also lead to otitis externa and otitis media.
These two conditions can be diagnosed in several ways. For instance, X-rays may be used to diagnose otitis media; an magnetic resonance imaging (MRI) may also be used to identify an accumulation of fluid or soft tissue growth in the middle ear.
Other ways of diagnosing these conditions include skin scrapings from the cat's ear flaps to test for parasites, and skin biopsies to check for autoimmune diseases. However, the single most important tool for diagnosing otitis externa and otitis media is a microscopic examination of the ear discharge (aural exudate).