544 DISEASES/DISORDERS
Suppurative: purulent and malodorous exudates; erosion and ulceration of the epithe-
lial lining; frequently associated withPseudomonas aeruginosainfection; painful (Fig-
ure 37.4).Inflammation, pain, pruritus, and erythema of the pinnae and external canals.
Aural hematoma.
Swelling of the canal leading to stenosis.
Cerumen gland hyperplasia (Figure 37.5).
Fibrosis and ossification of the auricular cartilage; canals palpate as firm and thick-
ened.
Holding of the pinnae down and/or head tilt toward affected side (if unilateral).
Chronic otitis externa in dogs results in tympanic membrane rupture (71%) and otitis
media (82%) (one study).
Allergic dermatitis: most common cause of otitis externa in dogs.
Polyps and ectoparasites: most common cause of recurrent otitis externa in cats.
Otitis Media
Intact tympanic membrane: bulging tissue with evidence of fluid and/or gas caudally;
membrane may be opaque; fluid may be purulent or hemorrhagic (Figure 37.6).
Swelling of the pars flaccida: may indicate increased pressure in the middle ear; com-
monly seen with primary secretory otitis media in the cavalier King Charles spaniel
(Figures 37.7–37.9).Ruptured tympanic membrane: discharge into canal or bullae filled with debris (Fig-
ure 37.10).
Deafness.
Pain on palpation of bullae or opening of the mouth.
Pharyngitis, tonsillitis, or discharge through auditory tube (Figure 37.11).
Lymphandenopathy if severe or chronic.
Otitis Interna
Deafness.
Neurologic findings:
Vestibular (cranial nerve VIII) deficits: nystagmus, head tilt (ipsilateral), ataxia,
anorexia or vomiting, and reluctance to move the head (Figure 37.12)
Facial nerve (cranial nerve VII) deficits: paresis/paralysis of eyelids, lips, tongue,nares; reduced tear production; miosis, ptosis, protrusion of the nictitans, and
enophthalmos (Horner’s syndrome) (Figure 37.13).DIFFERENTIAL DIAGNOSIS
Otitis Externa and Media
Primary causes:
Parasite:Otodectes cynotis,Demodexspp., Sarcoptes scabiei,Notoedres cati,and
Otobius megnini(Figure 37.14).