Ear disease in cats and dogs Flashcards
- 4 types of factors to consider when approaching a case of otitis externa.
- Primary
Secondary.
Predisposing.
Perpetuating.
Primary factors.
- Most common primary factor of otitis externa.
– others?
Directly induce otitis externa.
- Allergic skin disease (atopic dermatitis most common, CAFR, contact dermatitis).
– ectoparasites –> Otodectes (rarely demodex), FB.
– Uncommonly tumours, hypothyroidism, keratinisation disorders incl. endocrine, autoimmune.
Secondary factors.
- examples.
Do not create disease, aggravate it.
Only addressing secondary factors alone may not resolve ear disease.
- Ear microclimate supports complex resident population of microorganisms so easily upset…
- e.g. by inappropriate topical meds.
- e.g. microbial overgrowth.
– Staph. and Malassezia can be isolated from normal ear canals.
- e.g. opportunistic infection e.g. pseudomonas.
Predisposing factors.
- examples.
Increase risk of otitis externa.
- ear conformation e.g. cockers and crosses, bulldogs.
- humidity in ear canal.
- inappropriate (over) cleaning – irritant.
- hypertrichosis? – management harder.
- Predisposition to keratinisation disorders.
- Trauma.
- Neoplasia - reduced air flow.
Perpetuating factors.
- examples.
Keep disease going.
- Large population of specialised sebaceous glands which produce cerumen:
– sensitive to inflammation and will up-regulate w/ minimal stimulus.
– excessive production and accumulation of cerumen and ear canal discharge.
- Altered components of cerumen encourages microbial overgrowth.
- Excessive cleaning or use of irritant or inappropriate meds will encourage process.
- In chronic proliferative otitis externa.
– excessive granulation tissue.
– scarring, stenosis, deformity.
– calcification of cartilage.
- Glandular tissues undergo inflammatory and hyperplastic changes.
– increases stenosis.
- Persistent ulcerative otitis externa.
- Involvement of the middle ear.
Otitis externa clinical signs.
Uni or bilateral.
- head shaking, scratching, rubbing, yelping.
Vertical canal obstruction by moderate to severe hyperplasia.
Ear canal may be firm on palpation due to hyperplasia, fibrosis and calcification.
Discharge - ceruminous, profuse foul-smelling, purulent, yellow-green, dark and tarry.
Otitis media/interna clinical signs.
Pain on opening mouth, or eating, or on palpating ears.
Neuro signs:
- facial nerve paralysis, Horner’s syndrome, Hearing loss (adapt to hide this), vestibular e.g. head tilt, deafness, ataxia, strabismus, nystagmus.
Investigation of ear disease - what else do we need to know?
- Presence of pruritus / skin lesion elsewhere.
- Previous clinical signs?
- Presence of systemic signs.
- Other animals in household affected?
- Previous or current meds?
- Ectoparasite control programme?
Investigating ear disease - PE.
Examine whole body and skin surface.
Check pinnae in detail (scabies, vasculitis).
Determine if there is pain on palpation of the base of the ear due to fibrosis / calcification.
Examine entrance of vertical canal w/ good light.
Check integrity of both ear canals and tympanic membranes.
Otoscopy can be uncomfortable or painful so may need to sedate.
Open mouth as wide as possible - pain in temporo-mandibular joint can be seen w/ otitis media and other diseases.
Investigating ear disease - dx tests.
Cytology of ear discharge - tape impressions of skin folds e.g. pinna lesions.
Culture and susceptibility testing of discharge if:
- already treated w/ multiple abx / antiseptic treatments. (topical/systemic).
- risk of antimicrobial resistance.
- rods on cytology (pseudomonas, e. coli, klebsiella, proteus).
Remember normal ears contain Malassezia, Streptococci, Staphylococci.
What must be done to allow full assessment of the ears?
Clean ears:
- may require sedation, GA etc.
- if any doubt about TM integrity, use sterile saline to flush.
May need to assess ear canal and reverse stenosis first - oral preds.
What is indicated in terms of diagnostics if middle ear disease is suspected?
Radiography / CT scan of tympanic bullae.
Under GA.
May see thickening, lysis, calcification etc.
Otitis media may be present w/o radiographic changes/outward clinical signs.
What does a healthy ear canal look like?
What does a healthy TM look like?
Smooth, pink, reasonably hairless, reasonably clean, open canal.
Slightly translucent, greyish, clean, sometime vascular membrane.
Investigating ear disease w/ radiography, CT, MRI.
Otitis media not always associated w/ radiographic changes - but if is, can be prognostic indicator.
Thickened or mineralised ear canal.
Stenosis / occlusion of external canal.
Sclerosis of petrous temporal bone.
Thickening, sclerosis of tympanic bullae.
Lysis of tympanic bullae.
Soft tissue opacity w/in bullae.
- What is chronic ear disease typically associated with?
- Degree of signs in early stages of disease?
- What to do if increase cerumen due to inflammation of ear canal due to allergic skin disease?
- Allergic skin diseases and otitis.
- May be low but with high degree of pruritus.
- Establish if a secondary infection is actually present with cytology as not to unnecessarily prescribe antimicrobial ear drops. Doing so may exacerbate the problem either by disturbing the microflora or casing a contact reaction.
