Chapter 61 Otitis Media and Otitis Interna
Otitis media: Otitis media is defined as inflammation of the middle ear and is an important perpetuating cause of recurrent otitis externa.
• Otitis media occurs as a direct extension from an existing otitis externa through a ruptured tympanic membrane.
• In a recent study, 72.5% of the ears in dogs with otitis media diagnosed by a myringotomy had an intact tympanic membrane.
ETIOLOGY
• Bacteria: The most common etiology of otitis media is a bacterial infection. The two most common bacterial isolates are Staphylococcus intermedius and Pseudomonas spp.
• Yeast may be a significant pathogen, and in one study was the sole isolate in 23.7% of the middle ears of dogs with otitis media.
• Congenital palatine defects (secondary cleft palate) have been associated with radiographic signs of middle ear disease.
• Primary secretory otitis media has been reported in the Cavalier King Charles spaniel. Clinical signs include moderate to severe pain in the head or cervical region; neurologic signs such as ataxia, facial paralysis, nystagmus, head tilt, or seizure; otic pruritus; otitis externa; and fatigue. In most cases in the study, a bulging but intact tympanic membrane was observed. A highly viscous mucous plug was removed with ear forceps or a suction catheter. Removal of the mucous plug and flushing the middle ear had to be repeated up to five times for resolution.
• Neoplasia and polyps can cause otitis media. Tumors present in both the ear canal and tympanic bulla can be malignant. Inflammatory polyps are common in the cat, whereas they are relatively uncommon in the dog.
• Otoliths (mineral opacities) of the middle ear have been reported in three dogs; however, their significance is unknown, since only one dog had clinical signs of vestibular disease.
• Cholesteatomas are abnormal growths of the epithelium within the middle ear consisting of keratinizing stratified squamous epithelium, inflammatory cells, and ceruminous debris. These may occur congenitally or secondary to chronic otitis media and require surgical removal.
CLINICAL SIGNS
Otitis Media
• Signs of recurrent otitis externa include discharge from the external ear canal, pawing or rubbing of the affected ear, head shaking, and pain.
• Specific clinical signs indicative of otitis media are facial nerve paralysis and Horner’s syndrome. Injury to the facial nerve, as it courses near the middle ear, produces clinical signs such as drooping of or ina-bility to move the ear or lip, drooling of saliva, or decreased/absent palpebral reflex. Horner’s syndrome is due to injury to the sympathetic nerve fibers, which course near the middle ear, and is characterized by ptosis, miosis, enophthalmus, and protrusion of the nictitating membrane.
• Keratoconjunctivitis sicca (KCS) may occur if the parasympathetic nerves that innervate the tear gland are injured. The parasympathetic nerve fibers course with the facial nerve. Tear production can be evaluated with the Schirmer tear test.
Otitis Interna
• Signs of otitis interna are those typically associated with peripheral vestibular syndrome and include a head tilt, circling, falling, or rolling toward the affected side; horizontal or rotary nystagmus with the fast phase away from the affected side; and asymmetric ataxia with strength preserved (Table 61-1).
Table 61-1 VESTIBULAR SIGNS ASSOCIATED WITH INNER EAR VS. BRAIN STEM LOCATIONS
| Sign | Inner Ear | Brain Stem |
|---|---|---|
| Head tilt | Present | Present |
| Circling | Present | Present |
| Falling, rolling | Present | Present |
| Positional strabismus | Present | Present |
| Nystagmus | Usually spontaneous and type (horizontal, rotary) does not vary with head position | Usually not spontaneous but found with changes in head position; type (horizontal, rotary, vertical) varies with head position |
| Conscious proprioception | Normal | Delayed or absent |
| Horner’s syndrome | May be present | Usually absent |
| Gait changes | Mild to severe ataxia | Ataxia and weakness |
| Postural reactions (e.g., hopping, hemiwalking, wheelbarrowing) | Normal if examined slowly | Weak or absent |
| Cerebellar signs (hypermetria, head intention tremors) | Absent | May be present |
DIAGNOSIS
History
• Obtain a thorough history in order to establish the age of onset, duration of clinical signs, and the extent of the involvement of the skin (such as pruritus), to be able to identify the primary underlying dermatologic disease. See Chapter 59 for details on the primary underlying diseases causing otitis externa.
Physical Examination
• Perform a dermatologic examination to identify an underlying disease, such as parasitic disease, allergic disease, keratinization disorder, endocrine disease, or autoimmune disease.
• Perform a thorough physical examination and include the lymph nodes, oral cavity, and nasopharyngeal region.
• Perform a neurologic examination to evaluate for signs of facial nerve paralysis or Horner’s syndrome, which would be consistent with otitis media, as well as nystagmus and vestibular disease, which would support otitis interna.
• Perform an otoscopic examination to evaluate the external ear canal and tympanic membrane. The examination is performed with a hand-held otoscope or video otoscope (see under Video Otoscopy, following). Palpate the external ear canals to determine if there is any calcification indicating chronic disease.
• In addition, an otic examination may not be possible without sedation or general anesthesia, due to pain.
