Inflammation and infection of vertical and horizontal ear canal and middle ear (tympanic bulla) by Pseudomonas species bacteria.
Systems. Infection can cause otitis interna with loss of hearing/damage to vestibular system (neurologic signs). Pain can cause behavioral changes/difficulty eating or chewing, leading to weight loss/depression. Infection can invade surrounding soft tissue/bone causing cellulitis/para-aural abscess. Keratoconjunctivitis sicca and facial nerve paralysis can develop from otitis media.
Geographic Distribution. Worldwide. Gram-negative suppurative otitis may be more common in tropical climates.1
Species. Dogs and rarely cats.
Breed predilection. Any breed, but more common in breeds with higher prevalence of such hereditary skin diseases as allergic and seborrheic dermatitis.
Age and Range. Can occur at any age in dogs with or without underlying skin disease as trigger. Young cats with ear polyps or older cats with ear tumors at greater risk.
Gender. No sex predilection.
Causes of otitis externa/media are typically divided into 3 categories: predisposing, primary, and perpetuating factors (see box).
Primary causes: Diseases for which involvement of ear pinna/canal is a "target sign." Most common are hypersensitivity disorders, parasites, keratinization and glandular disorders, foreign bodies.
Predisposing causes: Conditions leading to changes in moisture, humidity, secretions, trapping debris in ear. Factors can exist solely or develop as result of primary disease (e.g., allergic otitis externa causing stenosis of canal). Most common predisposing causes are stenosis of ear canal, floppy ears, excessive hair in canal, excessive cerumen, trauma to canal (e.g., hair plucking, excessive cleaning), obstruction by tumors/polyps, maceration of canal by moisture (i.e., swimming), or granulation tissue.
Perpetuating causes:Most commonly microbial infections that require treatment while a primary ear disease and/or predisposing condition is addressed. If left untreated, ear disease will not resolve. Most common perpetuating cause is overcolonization of the canal with bacteria and/or yeast.
Otitis media most commonly results from extension of otitis externa through the tympanic membrane. This membrane will heal and sequester bacteria and debris in the tympanic bullae. Some factors in Pseudomonas ear infections remain unknown. In author's experience, treatment-related causes of persistent infection include inadequate treatment of initial infection, lack of deep ear cleaning, subtherapeutic doses of fluoroquinolones, use of potent aminoglycoside or fluoroquinolone-glucocorticoid otic preparations as first-line treatments for non-gram-negative infections, and lack of follow-up care.
History. Recurrent otitis externa, head shaking and scratching, odor, facial pyotraumatic lesions, aural hematoma, pain on opening mouth, reluctance to chew hard food or toys, yelping or avoiding petting on the head or ears, head tilt, behavioral changes (irritability, hiding), depression, loss of hearing, stridor.
Physical examination. Pain not pruritus common in gram-negative otitis externa/media. Pain on palpation/manipulation of pinna or canal, ulcerative lesions in canal, resisting having mouth opened, frantic head shaking, malodor, exudate in external canal or "fluid sound" when palpated, thickened canals/palpable obstructive soft tissue/calcification of ear canal, head tilt. Otitis media can be "silent;" with only presenting sign being a head tilt.