The cat has some important anatomic differences from the dog. The obvious is that there is less breed variation in pinna
shape and conformation as well as relatively short and straighter ear canal. The manubrium is also less curved than in the
dog. The most clinically relevant differences related to treatment of otitis are in the middle ear where the cat has a much
different ventral tympanic bulla. The cat's ventral bulla is divided by an incomplete septum the divides it into two communicating
compartments. Dorsally the compartment is more lateral and ventrally more medial. A branch of the sympathetic nerve runs
in this septum and when damaged results in Horner's syndrome. This septum is more readily damaged when flushing, cleaning
or using instruments in the middle ear, which explains why Horner's syndrome is a much greater risk of complication in cats
with otitis. In addition the septum it is somewhat concaved saucer shaped with the convex surface facing ventrally. Any fluid
reaching the ventral compartment will have a much more difficult time being removed by positional changes or through the auditory
canal. It is important to realize once medication reaches the middle ear it is more likely to stay and if irritating more
likely to cause damage. As such it is wise to be very cautious when cleaning cat middle ears and avoiding harsh cleaning
ingredients such as dioctyl sulfo succinate and ototoxic drugs.
The incidence of ear disease in the cat is reported as 2-6%, much lower than in the dog. Though no studies have compared chronic
otitis I would speculate that is even much lower compared to the incidence in dogs. The relative importance of Otodectes
is also greater in cats than dogs which likely contribute to this observation. In a study of the ten most common feline skin
disease at a University Otodectes was the fourth most common with only flea related disease and dermatophytosis more prevalent.In
addition non Otodectes otitis externa was roughly one fourth the frequency. The low incidence in cats likely reflects that
cats are not affected with many of the chronic skin diseases, such as hypothyroidism and hereditary based keratinization/epithelialization
disorders, which often affect dogs. Even allergy is much less common in cats than dogs and when cats do have allergy the
ear is not affected in the majority of cases. Why this difference between species is seen is unknown.
What is even more unusual in its difference from dogs is the role of secondary infections and perpetuating factors. Secondary
bacterial otitis plays a relatively minor role. In one study the most common bacterial pathogen isolated in 31 of 75 ears
was coagulase neg Staphylococcus while Pseudomonas was not a problem. Referrals for Pseudomonas otitis in cats are exceedingly
rare in my practice and we actually see more otitis media from Malassezia than bacteria alone in my practice. Several other
studies have shown Malassezia to be a significant problem in feline otitis. FADDIN EN.CITE One study cultured Malassezia
from 63 of 99 cases and 33 had only Malassezia cultured. When antibiotics are needed then clavamox and clindamycin generally
are preferred in cats as compared to dogs.
Demodex mites may be found in cats with otitis as well in cases with just mild excessive cerumen build up. When no otitis
is present and it is found in just mild ceruminous build up then no treatment is necessary. In some cases with otitis the
otitis will not respond until the ears have been treated with lime sulfur. Inflammatory PolypsInflammatory polyps are non
neoplastic masses of epithelial tissue, fibroblasts, macrophages, lymphocytes, plasma cells and neutrophils. The variety
of cells makes it easy to differentiate from neoplastic tissue with cytologic evaluation of a fine needle aspirate. It is
believed they most often arise from the mucosa of the middle ear or auditory tube. The exact cause is unknown though in some
cases chronic inflammation from chronic otitis or upper airway disease is believed to be a factor. Cases often occur that
had no prior otitis or upper respiratory symptoms. Though one study found no evidence of a viral etiology a role for virus
as a cause or triggering factor has not been ruled out. Cats are more commonly affected by inflammatory polyps than dogs.
They tend to arise from a small pedicle but enlarge and then can extend into the external ear canal or pharynx. They occur
more in young cats, though may be found from a few weeks to 15 years of age.
Clinical finding may relate to otitis externa/media or upper respiratory disease. Chronic or recurrent otitis with head shaking,
aural pruritus, discharge, nystagmus, Horners syndrome, head tilt may be seen. Though unilateral disease is more common some
cases may have bilateral ear disease and bilateral polyps. Some cats may have difficulty swallowing and one cat had secondary
pulmonary hypertension. In many cases the masses are visible in the ear canal or behind or under the soft palate. One recent
study revealed 38% of cats are deaf in the affected ear and this appears to be sensory deafness not conductive hearing loss.
Presently, there are 2 main treatment options for removal of inﬂammatory (nasopharyngeal) polyps: traction avulsion and surgery
usually by a ventral bulla osteotomy. Traction avulsion is believed to have a higher recurrence rate. Though studies have
not been done the recurrence rate may be affected by how the avulsion occurs and post avulsion treatment with systemic glucocorticoids.
When the ear canal contains the mass it is important to grasp the mass far down the stalk and try not to tear in into pieces
but keep the mass intact. Twisting the base while applying slow even traction is helpful to remove the mass intact. After
removal oral triamcinolone 0.1 to 0.2 mg/kg for four days then taper to eod is prescribed as well as topical ear drops with
glucocorticoids, usually dexamethasone 0.1% and antimicrobials selected based on cytologic findings.