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728 Otitis Externa

• For animals with appendicular OSA well the pain associated with the primary demonstrated the degree to which they will
tumor can be controlled.
○ With amputation alone, median survival ○ After metastatic disease is visible, survival be able to ambulate after amputation.
VetBooks.ir ○ When amputation, limb salvage, or SRS is times typically are < 2-3 months, regard- Technician Tips
is 4-5 months; the 1-year survival rate is
10%, and the 2-year survival rate is 2%.
When OSA is suspected, use caution when
less of therapy (palliative or aggressive).
combined with adjuvant platinum-based
minimize pain and risk of pathologic fracture.
chemotherapy, median survival improves • For most animals with axial OSA, prognosis positioning the patient for radiographs to
is similar or more guarded, depending on
to 10-12 months, and 2-year survival rate completeness of excision with surgery or
improves to 15%-25%. return to function with SRS. SUGGESTED READING
○ When local therapy is combined with • Mandibular OSA carries a better prognosis. Selmic LE, et al: Comparison of carboplatin and
single-agent doxorubicin, median survival With mandibulectomy alone, metastatic rate doxorubicin-based chemotherapy protocols in 470
is 8 months, the 1-year survival rate is is ≈60%, and median survival is ≈17 months. dogs after amputation for treatment of appendicular
35%, and the 2-year survival rate is 17%. The benefit of adjuvant chemotherapy is osteosarcoma. J Vet Intern Med 28:554, 2014.
○ Prognosis using combinations of uncertain. AUTHOR: Dennis B. Bailey, DVM, DACVIM
carboplatin/doxorubicin or cisplatin/ • Nasal and digital OSA might also have a EDITOR: Kenneth M. Rassnick, DVM, DACVIM
doxorubicin is comparable to that seen lower metastatic rate, but information is
with single-agent platinum therapy. limited.
○ Proximal humerus location, elevated serum
alkaline phosphatase level, monocytosis, PEARLS & CONSIDERATIONS
and lymphocytosis are negative prognostic
factors. Comments
○ With palliative care alone, survival times Animals that are non–weight-bearing lame
are up to 4-5 months, depending on how on a limb affected by OSA have already

Otitis Externa Client Education
Sheet

BASIC INFORMATION Clinical Presentation ○ Treatment errors: use of cotton-tipped
applications to clean ears, plucking hair
Definition HISTORY, CHIEF COMPLAINT from the ear canals
Acute or chronic inflammation of the • Otic pruritus manifests as head shaking, • Primary causes: conditions or disorders that
external ear canal that may also involve the scratching, or rubbing ears on the floor. initiate the inflammatory process
pinnae • Otic erythema, otic exudate and odor, otic ○ Allergic disease: atopic dermatitis, cutane-
pain ous adverse food reaction
Epidemiology • Vestibular signs, hearing loss, Horner’s ○ Parasites: O. cynotis, Demodex canis,
SPECIES, AGE, SEX syndrome, nystagmus, and facial paresis/ Demodex cati, Otobius megnini
Dogs, less commonly cats paralysis may occur with middle and inner ○ Foreign bodies
ear involvement. ○ Juvenile cellulitis
GENETICS, BREED PREDISPOSITION • Additional clinical signs (e.g., pedal pruritus, ○ Cornification disorders
• Canine: cocker spaniel, Brittany spaniel, and indicating primary underlying allergic ○ Endocrine disorders
many others disease) may be present and help with ○ Autoimmune diseases
• Feline: Himalayan and Persian cats determination of the primary cause of the ○ Masses: neoplasia, nasopharyngeal polyps
otitis externa. • Perpetuating factors sustain and aggravate the
RISK FACTORS inflammatory process, prevent resolution, or
• Swimming, moisture in the ear canal PHYSICAL EXAM FINDINGS worsens an already present otitis externa.
• Plucking hair from external ear canal • Alopecia and excoriations of the pinnae ○ Bacteria
• Thickening and/or calcification of the ear ○ Yeast
CONTAGION AND ZOONOSIS canals is indicative of chronic to end-stage ○ Progressive pathologic changes of the ear
• Contagion: ear mites (Otodectes cynotis) are otitis. canal (e.g., stenosis, hyperplasia)
contagious among animals (p. 731). • Erythema, exudation, hyperplasia, stenosis, ○ Otitis media
• Zoonosis: zoonotic transmission of bacterial and ulcerations of the ear canals • Successful treatment of otitis externa depends
infections from the ears of dogs to humans • Sometimes, pain when opening the mouth, on identification and on controlling or elimi-
is very uncommon. It is prudent to advise hearing loss, facial paralysis or paresis, head nating these factors and causes. Treating the
owners to wash their hands frequently or tilting, circling, Horner’s syndrome, and complicating infection without addressing
wear gloves while handing their pet with nystagmus the primary cause or eliminating the primary
known or suspected drug-resistant infectious cause without control of the secondary infec-
otitis externa. Etiology and Pathophysiology tion likely will result in treatment failure.
• Predisposing factors facilitate inflammation
ASSOCIATED DISORDERS by permitting alteration of the normal DIAGNOSIS
Allergic diseases (e.g., cutaneous adverse food microenvironment.
reaction, atopic dermatitis), aural hematoma, ○ Conformation: stenotic canals, exces- Diagnostic Overview
pyotraumatic dermatitis on face/neck, infectious sive hair in the ear canals, pendulous The diagnosis of otitis externa is based on
otitis media pinnae obtaining a complete history and assessment
○ Moisture of the results of the clinical and cytologic exam.

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