Dermatology Lecture 6 Flashcards
What is otitis externa?
Inflammation of the external ear canal
What is meant by a secondary cause of otitis externa?
A secondary cause is a factor that does not occur in the normal ear
What is meant by a primary cause of otitis externa?
Skin problem that directly causes otitis externa - treatment occurs through resolution of the disease
List five potential primary causes of otitis externa:
- Allergies 2. Endocrine 3. Keratinisation defects 4. Parasites 5. Foreign bodies 6. Neoplasms
What is the most common cause of otitis externa in dogs?
Atopic dermatitis
Name the likely cause of the otitis externa below:
Food allergy - approximately 20% of dogs with food allergy present with otitis externa alone
What are some of the major predisposing causes of atopic otitis externa?
- Confirmation
- Excessive moisture
- Treatement effects
How does hair predispose to otitis externa?
Excessive hair or knots occludes canal impairing ventilation + clearance - presence of hair does not mean that the dog will definately develop otitis externa
How does cerumen composition lead to otitis externa?
Certain breeds have more cerumen glands
How does conformation predispose to otitis externa?
Excessive cartilagenous folds and tightly folded pinna- creates a moist humid environment inside of the ear - this increases the risk of otitis
What is meant by a perpetuating cause of otitis externa?
Factors that prevent resolution of otitis and lead to a relapse
How can changes in the external ear wall be perpetuating causes of otitis externa?
Acute changes: oedema and hyperplasia
Chronic changes: Proliferative changes, canal stenosis, calcification of pericartilagenous tissue
What are the main perpetuating causes of otitis media?
- Proliferative changes
- Failure of self cleaning
- Ruptured tympanic membrane
- Otitis media
