Middle Ear Infection
Otitis Media

Although most cases of ear disease in our pets are a process involving the external ear canals, we have seen an increasing incidence of otitis media, or middle ear infection. This increase in patients, with middle ear disease, is likely due to improved imaging of the tympanic membranes (ear drum) through video otoscopy. This procedure allows better visualization and magnification of the external ear canal and the tympanic membrane.

Middle ear disease, in the cat, can be caused by an ascending infection secondary to upper respiratory disease. The inflammation, fluid accumulation, and infection can ascend up the auditory tubes (Eustachian tubes) into the middle ear. There is a build-up of fluid or pus behind the tympanic membrane (TM) increasing pressures. This is oftentimes noted as a "bulging" of the TM. This increased pressure can cause severe pain, much like a child with an ear ache. Cats will often shake their head, scratch at the offending ear, or tilt their heads toward the side affected.The external canal often appears normal. In addition to a bulging TM, there can be increased opacity, discoloration, thickening, or increased vascular patterns. Myringotomy, or opening the ear drum, is an important step in relieving the pressure and pain by removing the pus and fluids. Irrigation of the tympanic cavity (middle ear cavity) will also allow the clinician to identify the causative organism.

In the dog, most cases of middle ear disease is an extension of chronic, untreated or poorly treated external ear disease. This long-standing infection can penetrate the middle ear cavity through a defect in the TM. In some instances, the ear drum may be completely gone to inflammatory exudates. Again, not only is it important to rid the external ear canal of fluids and pus, but the middle ear , as well. The ear drum will regenerate quickly once the disease process has resolved. Topical antibiotics instilled into the outer ear canal is used routinely and successfully for external ear disease, but deeper instillation of aqueous antibiotics should always be considered. Treatment, concurrently, with systemic antibiotics and anti-inflammatory drugs is indicated. We recommend periodic (every 2-4 weeks) irrigation of the middle ear cavity with dilute povidone-iodine solutions (warmed) until all clinical signs of middle ear and external ear disease has resolved.

In both species, it is very important to understand and identify the underlying cause of the ear disease. Is there an underlying allergy, including a "food-related allergy" causing excessive production of cerumen (ear wax)? Is there an inflammatory polyp (common in cats) interfering with the normal drainage of the ear? Did the middle ear infection result from a respiratory infection several weeks ago?

Food-related disease, also known as cutaneous adverse food reaction, is one of the most important causes of external ear canal disease in the dog. Chronic and unrelenting changes in the anatomy of the ear canals will lead to direct extension oif the infection into the middle ear. Eliminating the offending food allergen from the diet is extremely important as the foundation for resolving this process.

Unfortunately, many of the anatomic changes, over time, can be irreversible leading to trapping of fluids and exudate in the ear canals and middle ear. Surgery is indicated if there is little chance of normalizing the ear canal. In some instances, removal of the outer wall of the external vertical canal, commonly known as a Zepp procedure or lateral ear resection, will allow improved drainage.

A tympanic bulla osteotomy is used if the middle ear cavity is filled with proliferative bone, fibrosis, or thickened membranes. Curetting this bony cavity will help remove the infective tissue and allow for improved drainage.

The accompanying photos show accumulation of pus in the lower or terminal horizontal canal of a cat and dog affected by middle ear disease (otitis media).