Otitis is applied as a general term to an inflammatory process of the ear.
In both dogs and cats (as in humans and other mammals), otitis is generally categorized by anatomic location within the ear canal into three distinct disease entities: otitis externa (external ear canal), otitis media (middle ear) and otitis interna (inner ear).
Otitis externa is an extremely common condition in both dogs and cats. It affects the skin that lines the ear canal and, as such, is considered a dermatological disease. It can come on suddenly (acute otitis externa) or smolder for extended periods of time (chronic otitis externa).
Any skin disease that affects the external ear canal can cause otitis externa. As such, allergic skin disease, keratinization disorders, and hypothyroidism are all considered primary causes. Other causes include trauma, foreign bodies, masses, and parasites, but allergic skin disease is by far the most common primary cause of this condition in companion animals.
Unfortunately, otitis externa is complicated by predisposing and perpetuating factors:
Conformation (narrow canal, pendulous ears, etc.), environmental factors (high humidity, excessive cleaning, etc.), and concurrent diseases (for example, those that affect normal immune function) can all predispose ears to otitis externa.
Perpetuating factors typically include yeast and bacterial infections as well as the presence of concurrent otitis media.
This inflammation of the structures of the middle ear tends to occur either when a chronic external ear infection breaches the eardrum and extends into the middle ear canal or when trauma leads to the eardrum’s rupture and subsequent inflammation. Less commonly, otitis media may be the result of an infection that spreads through the auditory tubes or, more rarely, through a bloodborne infection.
Otitis interna is an inflammation of the structures of the inner ear that, in pets, is most commonly caused by the extension of an otitis externa and subsequent otitis media or as a result of trauma.
Symptoms and Identification
One or both ears may be affected. Head shaking, pawing at or rubbing the affected ear(s), and cocking the head toward the most affected side are typical signs. Redness, itchiness and/or pain, and a malodorous discharge are usually noted.
Clinical signs and visual inspection are considered sufficient evidence for definitive diagnosis of otitis externa, but primary, predisposing and perpetuating causes must also be indentified, most typically via the following diagnostic tests:
- Otoscopic examination
- Culture and sensitivity
- Complete blood count (CBC)
- Blood biochemistry panel
- Testing for specific skin conditions, including …
- Thyroid testing
- Allergy testing
- Autoimmune panel
Pets who suffer this condition usually show all of the signs associated with otitis externa. However, they may also be feverish, suffer nerve damage that can manifest as a one-sided facial droop, and/or experience changes to the pupil on the affected side.
This process can be diagnosed by observing the eardrum with an otoscope and noting a discoloration, bulge, or rent in the membrane. After observing these changes and undertaking the basic diagnostic tests listed under otitis externa, above, X-rays and CT scans or MRIs may be necessary to evaluate this area more fully.
The most typical signs of otitis interna include loss of both equilibrium and hearing, but pain is a significant factor as well, as is circling or falling to one side. Evaluating the ear as for otitis externa and otitis media is the recommended diagnostic approach to otitis interna.
For dogs and cats, there is no specific breed predisposition to otitis. Some of the primary and predisposing causes of otitis externa, however, are more common in certain breeds. Conformational issues and allergic skin disease, for example, are well known to have hereditary origins.
Otitis is considered a highly treatable condition once primary causes have been identified and addressed. Excising a tumor, properly managing a wound, removing an offending allergen from the patient’s environment, replacing a patient’s thyroid hormone with a supplement, treating with an appropriate antimicrobial, etc.
In all cases, treatment should be specifically targeted to all predisposing and perpetuating causes as well. This is why topical and oral antibiotic, antifungal, and anti-inflammatory drugs are often required for treatment of otitis, despite the fact that the processes these drugs are aimed at are not responsible for the underlying disease.
In many cases of severe otitis externa, particularly where chronic otitis media is a perpetuating cause and pain is significant factor, past treatment may have proved insufficiently effective. For many of these patients, surgical treatment may be the only approach to achieving comfort.
In particular, a total ear canal ablation (TECA) is often recommended. This surgical technique involves the removal of the entire ear canal. And while it may yield significant hearing loss, most of these patients already experience so much pain (as well as considerable loss of hearing) that their overall quality of life is almost always dramatically improved by this approach.
The cost of diagnosis and treatment for otitis depends on many factors, including its primary cause, the duration of the disease state (how long the otitis has been active), geographic location (cost of living), standard of care (lower vs. higher standards of veterinary care), and whether specialty hospitals are employed (higher quality equipment, certified personnel, and board-certification for veterinarians specialized in the fields of surgery and oncology).
In general, otitis externa is considered less expensive than otitis media or otitis interna. This is largely a function of the fact that many cases of otiits media and otitis interna occur as complications of untreated, longstanding otitis externa. However, the need for more sophisticated (and expensive) imaging techniques to evaluate deeper anatomic regions is also a contributing factor.
Expenses for treatment of otitis range from $100 for simple, uncomplicated, acute otitis externa to several thousands of dollars should advanced imaging (CT or MRI) be required for evaluation.
Surgical treatment of an end-stage, chronic otitis externa with complications affecting the middle and inner ear tends to range from $2,000 to $5,000. Its significant expense is due largely to the fact that this surgical technique is always best performed by a board-certified veterinary surgeon.
There is no sure mode of prevention for otitis, save the application of careful breeding programs to help reduce any genetic perpetuation of its many primary and contributing causes. Identifying and managing these early, whenever possible, will positively affect the extent and severity of the disease and may even forestall –– if not completely prevent –– its progression.
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Scott DW, Miller WH, Griffin CE. Diseases of eyelids, claws, anal sacs, and ears. In: Muller & Kirk's small animal dermatology. 6th ed. Philadelphia, Pa: W.B. Saunders, 2001:1185-1235.