Page 74 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 5 · Surgery of the ear

Pinnal necrosis to sinonasal or nasopharyngeal disease, presumably due to
secondary dysfunction of the auditory tube (Detweiler et al.,
Necrosis of the pinna may be secondary to a number 2006; Shanaman et al., 2012; Foster et al., 2015). In most
VetBooks.ir (vasculitis, proliferative thrombovascular necrosis of the instances, OM in dogs is thought to result from the exten-
of underlying conditions, including ischaemic damage
sion of inflammatory disease from the external auditory
pinna, cryoglobulinaemia) or frostbite (Halliwell, 2013).
Clinical features of pinnal necrosis include cyanotic skin
that is cool to the touch, sloughing skin, wedge-shaped canal into the bulla via a perforated tympanic membrane.
ulcers of the pinnal tip or margin, bleeding and a Diagnosis
deformed notched appearance to the pinnal margin. The status of the tympanic membranes should be con-
Management of pinnal necrosis relies upon identification firmed in all cases of chronic/recurrent otitis. If oedema or
and control of the underlying cause. Medical management proliferative changes preclude visualization of the entire
of conditions such as pinnal margin vasculitis typically external canal to the level of the tympanum, topical anti-
includes use of immunomodulatory medications and the microbial therapy for the infection should be initiated,
rheological agent pentoxifylline. If necrosis is extensive or based upon cytological findings, and the patient should
if bleeding of the pinnal tips or margins cannot be be discharged on an anti-inflammatory regimen of oral
controlled with medical therapy alone, resection of the glucocorticoids. The potential for ototoxicity with topical
affected portions of the pinna via partial or complete anti microbials (such as aminoglycosides) should be con-
pinnectomy may be indicated. sidered, particularly if the tympanic membrane cannot be
visualized prior to initiating therapy (Oishi et al., 2012). The
patient should then be returned for otoscopic evaluation
Otitis externa and media in 2–4 weeks.
It is not uncommon for a tympanic membrane to
Otitis is a very common extension of cutaneous inflamma- appear to be intact upon otoscopic examination, due
tory disease in dogs, though less so in cats. For descrip- to sponta neous repair, a subtle tear or poor visibility during
tive purposes, it is often categorized as acute OE, chronic/ otoscopy. The newer fibreoptic otoscopes, when com-
recurrent OE and otitis media (OM). Clinically, the term pared with conventional otoscopes, allow superior visuali-
otitis most often implies the presence of a bacterial or zation of deep structures. They provide magnification and
fungal infection, although sterile otitis can result from mass a bright light source at the level of the tympanum, which
lesions (tumours, inflammatory polyps, foreign bodies), may reveal tympanic defects that would have otherwise
parasites, allergic diseases and irritating chemical or been missed with conventional otoscopes (Figure 5.4).
mechanical cleansing regimens. Primary secretory otitis
media (PSOM) or otitis media with effusion (OME) is a
breed-related condition resulting in sterile middle ear effu-
sion and is recognized primarily in the Cavalier King
Charles Spaniel (Cole, 2012). A similar condition has been
reported in brachycephalic animals and is presumed to be
the result of auditory tube dysfunction caused by anatom-
ical differences in the position and shape of the tympanic
bulla and auditory tube, and respiratory tract mucosal
swelling (Hayes et al., 2010). Bacterial and fungal (yeast)
infections of the ear canals are thought to be secondary
problems in the overwhelming majority of cases, and it is
of utmost importance to control the primary otic disease
in order to curtail repeated infections.
(a)
Aetiology
In cases of recurrent infection, all potential predisposing
factors and direct/indirect causes of otic inflammation and
immunosuppression must be considered. Infection may
result when inflammation is persistent within the external
auditory canal, regardless of the inciting cause. However,
chronic/recurrent infectious otitis is most commonly asso-
ciated with an uncontrolled primary allergic disease (e.g.
atopy, adverse food reaction), endocrinopathy or iatrogenic
immunosuppression. Chronic OE may lead to progressive
pathological changes – such as glandular hyperplasia,
fibrosis and osseous metaplasia – that necessitate surgical
intervention. In such cases (referred to as ‘end-stage
otitis’), surgery may be the only option for correction of
stenosis and the intractable secondary infections that
result from a disrupted auditory canal microclimate. (b)
OM, defined as inflammation of the tympanic bulla, is a
common sequel to severe or chronic OE. Primary OM is 5.4 Otoscopic examination. (a) Normal tympanic membrane.
(b) Ruptured membrane. As is often the case, the diseased
thought to be rare in dogs but is implicated in cats with tympanum is tearing away from its rostral attachment to the
inflammatory polypoid disease (see below). Middle ear manubrium. This may be interpreted as an intact tympanum if the
effusion in dogs and cats may also occur secondary otoscopic visual field is obscured or the light source is poor.

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