What are the 4 types of factor to consider with otitis externa?
Primary
Secondary
Predisposing
Perpetuating
What are some common primary factors that directly induce otitis externa?
- Allergic skin is the most common cause of chronic otitis
- Atopic dermatitis most common
- Cutaneous adverse food reaction
- Contact dermatitis – topicals
- Ectoparasites
- Foreign bodies
What are some uncommon primary factors that directly induce otitis externa?
Tumours
Hypothyroidism
Keratinisation disorders (including endocrine)
Autoimmune
What are some secondary factors that aggravate otitis externa?
- The ear microclimate supports a complex resident population of microorganisms - easily upset, for instance with inappropriate topical medications
- Microbial overgrowth – staphylococci species and Malassezia can be isolated from normal ear canals
- Opportunistic infection, such as pseudomonas
What are the predisposing factors of otitis externa?
- Conformation of the ear
- Humidity in the ear canal
- Inappropriate over cleaning
- Hypertrichosis
- Predisposition to keratinisation disorders
- Trauma
- Neoplasia
What are some perpetuating factors of otitis externa?
- Specialised sebaceous glands which produce cerumen
- Altered components of the cerumen encourages microbial overgrowth
- Excessive cleaning or use of irritant or inappropriate medication
- Glandular tissues undergo inflammatory and hyperplastic changes – increases stenosis
- Involvement of the middle ear
How do glands that produce cerumen perpetuate otitis externa?
Sensitive to inflammation and will up-regulate their synthetic activity with minimal stimulus
Excessive production and accumulation of cerumen and ear canal discharge
What is chronic proliferative otitis externa characterised by?
- Excessive granulation tissue
- Scarring, stenosis and deformity of the ear canal
- Calcification of the cartilage
What are the neurological signs of otitis externa?
- Facial nerve paralysis
- Horner’s syndrome
- Hearing loss
- Vestibular signs
What are the clinical signs of otitis externa?
- Head shaking
- Scratching or rubbing ears
- Yelping when handled
- Vertical canal may be obstructed by moderate to severe hyperplasia
- Ear canal may be firm on palpation due to hyperplasia, fibrosis and calcification
- Discharge
- Pain on opening the mouth of eating or on palpating the ears
How and what is otitis externa assessed at physical examination?
- Whole body and skin surface
- Pinnae
- Pain on palpation of the base of the ear due to fibrosis/calcification
- Entrance to the vertical ear canal
- Integrity of both ear canals and the tympanic membranes
- Otoscopy
- Open the mouth - pain in the temporo-mandibular with otitis media
- Diagnostic tests
- Clean the ears to fully asses the canals and tympanic membranes – under sedation, GA, if there is any doubt about TM integrity, use sterile saline to flush
- Reverse stenosis?
- If the middle ear disease is suspected, radiography/CT scan of the tympanic bullae
What diagnostic tests can be used to investigate otitis?
- Cytology of ear discharge – take impressions of skin folds, such as pinnae
- Culture and susceptibility of ear discharge
When is auricular discharge culture and susceptibility tested?
- Already treated with multiple antibiotic/antiseptic treatments
- Risk of antimicrobial resistance
- Rods on cytology
What is challenging about diagnostic tests into otitis?
Normal ears contain Malassezia, Streptococci, Staphylococci
What can be seen on CT and MRI that could indicate otitis media?
- Thickened or mineralised external ear canal
- Stenosis/occlusion of external canal
- Sclerosis of petrous temporal bone
- Thickening, sclerosis of tympanic bullae
- Lysis of tympanic bullae
- Soft tissues opacity within bullae
What is a feline specific aspect of the middle ear?
Cats have a bone that separates their middle ear into almost 2 compartments
How are allergic skin disease and chronic ear disease linked?
- In early stages of allergic skin disease, the degree of pruritis of the pinnal area exceeds the involvement of the ear canals
- Inflammation can lead to increased cerumen production - not necessarily mean secondary infection present
Do you need to use antimicrobial ear drops in chronic ear disease?
Could exacerbate the problem either by disturbing the microflora or causing contact reaction
How is chronic ear disease managed?
- Judicious use of ear cleaner and topical anti-inflammatory preparations may help to control head shaking and scratching
- In some cases, systemic glucocorticoids may be the only means of controlling clinical signs
- With repeated episodes, consider performing an elimination diet trial to investigate for CAFR
What are some underlying causes of recurrent otitis externa with keratinisation?
Hypothyroidism, hyperadrenocorticism and sex hormone imbalances
What are the aims of therapy with ear disease?
- Kill microorganisms in ear canal and middle ear
- Keep ear canal open so topical solutions can reach deeper tissues and air can circulate
- Reduce inflammation, discomfort and cerumen production
What is applied to the ears after cleaning in otitis?
Topical medication – combinations of steroid, antibiotic and antifungal agents (NSAIDs are not helpful for otitis)
Is systemic antibiotics used for otitis?
Little benefit in otitis externa
Which antibiotics are used to treat pseudomonas otitis?
Marbofloxacin
Orbiflaxacin
Gentamycin
Polymyxin B
Tris-EDTA may help make antibiotic more effective
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