Otitis media results from a multitude of factors that cause inflammation of the lining of the tympanic cavity and\/or structures of the middle ear, including infections, middle ear polyps, and neoplasms. Cats with otitis media can be asymptomatic or exhibit clinical signs of otitis externa, neurologic deficits, or upper respiratory tract disease. A therapeutic challenge is presented by cats\u2019 unique, almost complete, septum bulla in the ventral cavity of the middle ear. Diagnosis of otitis media relies on visualization of material in the middle ear by otoscopy or imaging. Treatment requires management of the underlying cause as well as removal of the material in the middle ear by minimally invasive (e.g., myringotomy and bulla lavage) or surgical (e.g., ventral bulla osteotomy) techniques.<\/p>\n
Take-Home Points<\/strong><\/p>\n <\/div><\/div><\/p>\n Otitis media (OM) is inflammation of the structures (auditory ossicles, septum bulla) and\/or modified mucosal membrane of the middle ear cavity, known as the tympanic cavity, frequently accompanied by fluid accumulation.1,2<\/sup> The causes are multifactorial and include ascending infections associated with nasopharyngeal disease; neoplasia; inflammatory aural polyps; descending infections from the external ear canal; or, rarely, hematogenous spread.2-5 <\/sup>Clinical signs of OM are often missed because cats may exhibit nonspecific signs.6 <\/sup><\/span><\/p>\n Diagnosis requires advanced imaging in most cases or video otoscopy (VO). The middle ear is lined by a modified respiratory mucosal epithelium that comprises 3 areas7<\/sup>: the epitympanic recess, which houses the 3 auditory ossicles; the midsection (tympanic cavity proper), which is directly adjacent to the <\/span>tympanic membrane and contains the manubrium of the malleus (<\/span>FIGURE 1<\/b><\/span>); and the ventral cavity, which is the largest area and occupies the ventral portion of the tympanic bulla and contains a bony septum (septum bulla). The septum bulla is almost complete in felids, creating dorsolateral and ventromedial compartments (DLC and VMC, respectively) that communicate via 2\u00a0small openings.7<\/sup> The unique septal anatomy of cats warrants special consideration when diagnosing and managing OM.<\/span><\/p>\n FIGURE 1. A normal-appearing tympanic membrane. The \u201ccomma\u201d (arrowhead) represents the manubrium of the malleus, which attaches to the umbo of the pars tensa of the tympanic membrane. The tympanic membrane appears intact and transparent, affording visualization of the manubrium.<\/p><\/div>\n In general, the etiology of OM can be classified as primary or secondary and as ascending, descending, or hematogenous (according to the route of infection or material migration into the middle ear) (<\/span>TABLE 1<\/b><\/span>). Primary OM in cats is thought to occur by auditory tube dysfunction resulting from ascending infectious or inflammatory processes, and secondary OM is thought to occur by descending (e.g., external ear disease) or hematogenous routes.8<\/sup><\/span><\/p>\n In humans, auditory tube dysfunction plays a major role in the pathogenesis of OM with effusion.9,10 <\/sup>The auditory tube equalizes pressure, ventilation, and mucociliary clearance of middle ear secretions.11<\/sup> Disruption of these functions catalyzes the development of OM. For humans with allergic rhinitis, chronic rhinosinusitis, or upper respiratory infection, risk for development of auditory tube dysfunction is higher.12<\/sup> A similar role is suspected to occur in cats; experimental inoculation of bacterial endotoxin and obstruction of the auditory tube has led to high rates of OM.13<\/sup> Other studies have shown that a relatively high proportion of cats with OM have sinonasal disease (28%)3<\/sup> and exhibit nasopharyngeal signs (18% to 45%).14,15 <\/sup>Although the retrospective nature of these studies does not prove a causal relationship between upper respiratory disease and OM, it is suspected that ascending routes of infection likely contribute to the pathogenesis of OM in cats.3,14-16 <\/sup>Another, rarer, cause of auditory tube dysfunction in cats is soft palate abnormalities.17<\/sup><\/span><\/p>\n Secondary OM resulting from extension of otitis externa (OE) is believed to be less common in cats than dogs.18<\/sup> The pathogenesis involves a ruptured tympanic membrane, which permits microorganisms and material to transmigrate from the external ear into the middle ear. In multiple studies, the prevalence of clinical signs or examination findings consistent with external ear disease varies greatly in cats with OM, ranging from 15% to 79%.2,3,6,14,15,19,20<\/sup> Causes of descending OM include infectious OE, ear polyps, Otodectes cynotis<\/i> infestation, aural masses, cholesteatomas, allergic otitis, and foreign bodies.8<\/sup> OM acquired via the hematogenous route of infection is exceedingly rare in cats but has been reported.21<\/sup><\/span><\/p>\n The prevalence of OM in cats is difficult to ascertain; however, in a retrospective postmortem study, 1.7% (59\/3442) of cats had OM and otitis interna (OI) without ear polyps, and only 10% of those cats had neurologic signs referrable to OM\/OI while 29% had external ear disease.19<\/sup> Later studies have found prevalence rates of OM to be higher; rates vary from 32% in cats receiving computed tomography (CT) in a veterinary hospital, 28% in cats with sinonasal disease, 10% in hoarded cats, and 28% in cats exhibiting vestibular syndrome.3,6,15,20 <\/sup>OM is likely underreported due to the absence of clinical signs in some cats and is discovered incidentally during routine imaging studies.6<\/sup><\/span><\/p>\n\n
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<\/a>Etiology of Otitis Media<\/h2>\n
<\/a><\/p>\nPrevalence of Otitis Media<\/h2>\n
Clinical Signs of Otitis Media<\/h2>\n