Otitis Externa Flashcards
What 5 openings will you find in the tympanic bulla?
- Cochlear (round) window
- Vestibular (oval) window
- Bulla septum
- Eustachian tube
- Promontory
What makes up the inner ear?
- Bony labyrinth
- cochlea
- semicircular canals
- vestible
- Membranous labyrinth
- utricle
- saccule
- ampulla
- crista
Describe the tympanic membrane
- pars flaccida - smaller upper part
- pink, loosely attached region forming dorsal quadrant containing small b.v.
- pars tensa - firmly attached
- thin, tough, pearl-gray structure with radiating strands
Define otitis
- inflammation of the ear
- externa = ear canal
- media = bulla
- interna = canaliculi and/or cochlea
- it is a clinical sign and NOT a disease
- otitis externa is one of the most common disorders in medicine
What are the predisposing factors for otitis externa?
-
Conformation:
- pendulous ears
- excessive hair
- on pinna (Cockers)
- in canal (Poodles, terriers)
- stenotic ears
- breed related
-
Excessive moisture and humidity
- swimmer’s ear
- humid climate
- Excessive cerumen production
-
Inappropriate treatment
- trauma from applicators
- topical irritants (propylene glycol)
- over treatment
- hair plucking, over cleaning
-
Obstructive ear dz (can be primary too)
- neoplasia
- polyps
- FB
-
Systemic dz
- catabolic states
- immune suppression (FIV, FeLV, neoplasia)
- debilitation
Describe Otodectes cynotis
- aka “ear mite”
- non-burrowing psoroptid mite
- obligatory parasite
- 50% of OE in cats, 5-10% in dogs
- survive on skin surface
- protected by thick, brown crust
- feed on lymph and blood
- more common in animals < 1 yr of age
Describe Otobius megnini
- aka “spinous ear tick”
- SW US
-
larvae and nymphs induce inflammation
- larvae live in ear canal 7 mo before molting to nymphs
- drops to ground as an adult
- also reported in horses, cows, llamas
Describe Eutrombicula alfreddugesi
- aka “chiggers”
- bite causes irritation and variable pruritus
- legs, feet, head, ventrum
- size of a head of a pin
- seasonal - late summer/fall
- contact w/ woods and fields
- orange-red in color
Describe Otodemodicosis
- more common in cats (D. cati)
- Ceruminous otitis externa
- Suspect immunosuppressive dz
- FeLV, FIV, diabetes, neoplasia
- Evident on an ear swab
- do not need to scrape the ear!
Describe Sarcoptes scabiei var. canis
- aka “canine scabies”
- usually ear tips
- can be OE also
- severe pruritus
- female burrows in epidermis and lays eggss
- thick, yellow crusts
Describe Notoedres cati
- aka “feline scabies”
- medial proximal pinnae
- face, eyelids, neck, feet, perineum
- female mites burrow
- intense pruritus
- highly contagious
- easy to find
- abundant mites
What is the etiology for foreign body- induced otitis externa? Describe the clinical signs and treatment for this.
- Etiology:
- plant awns (barley)
- insect
- sand
- dry medications
- C/S:
- acute/chronic unilateral otitis
- Tx:
- remove the FB
- topical abx
Describe intraluminal tumors
- relatively uncommon
- dogs
- obstructive lesions
- ulceration and necrosis
- malignant: cats>dogs
- ceruminous gland adenocarcinoma
- SCC
- mast cell tumors
Describe nasopharyngeal polyps
- Etiology:
- congenital
- bacterial
- calicivirus
- C/S:
- chronic uni/bilateral otitis
- mass in ear canal
- head tilt
- Tx:
- surgery
Describe apocrine cystomatosis
- cysts of apocrine glands
- C/S:
- adult animals
- solitary, well-circumscribed, smooth, bluish tense swelling
- concave surface of pinna
- vertical ear canal
- uni/bilaterally
- Tx:
- benign neglect
- surgery
Describe the etiology of allergen-induced otitis externa. What are the clinical signs and treatment for this?
- Etiology:
- food allergy
- atopic dermatitis
- contact allergy
- drug reactions
- C/S:
- chronic bilateral otitis
- dermatitis
- Tx:
- tx the allergy
- tx the infection
Describe atopic dermatitis as a factor for otitis externa
- Erythema and inflammation
- pinnae
- vertical canal
- initial clinical sign
- entire ear canal
- more chronic
- 50% of atopic dogs have bilateral OE
What is the percentage of food allergy cases that have OE?
80%
Is contact allergy a common etiological factor for OE? How is it treated?
- no, it is not common
- Topical tx:
- neomycin/gentamycin
- miconazole 1%
- propylene glycol
- in many products
What are some examples of disorders of keritinization that result in OE?
- primary idiopathic seborrhea
- hypothyroidism
- sex hormone imbalance
- lipid related conditions
Describe primary idiopathic seborrhea
- incr cerumen production
- altered cerumen composition
- delayed desquamation and stenosis
- often progresses to calcifying OE and OM in the Cocker spaniel
Describe the etiology, pathogenesis, clinical signs, and treatment for endocrinopathy-induced OE
- Etiology:
- hypothyroidism
- sex hormone imbalance
- Pathogenesis:
- incr mucin deposition in dermis
- hyperplasia/hyperkeratosis of epidermis
- altered fatty acids productions
- C/S:
- chronic bilateral otitis
- dermatitis
- Tx:
- hormone supplement
- surgery
What are three autoimmune diseases that can cause OE?
- Pemphigus foliaceus
- Pemphigus erythematosus
- Systemic lupus erythematosus
Describe juvenile cellulitis
- Puppies 3-16 wks old
- older dogs have been reported
- vesiculopustular dz
- unknown etiology
- Dachshunds, Golden Retrievers, Pointers
- Purulent otitis with head and facial lesions
- Blepharitis, lymphadenopathy
What are some secondary factors that can cause OE?
- infection secondary to the inflammatory process
- bacteria
- yeasts
What are some bacteria can cause OE?
- S. pseuintermedius (30-50% of cases)
- Proteus mirabilis
- Pseudomonas spp.
- Escherichia coli
- Klebsiella spp.
- Corynebacterium spp.
What are some yeast species that may cause OE?
- Malassezia pachydermatis (found in normal canine/feline ears)
- Candida albicans
What are some pathologic changes that are perpetuating factors of OE?
- Epidermal
- hyperkeratosis
- hyperplasia
- epithelial folds
- Dermal
- edema and fibrosis
- Adnexal
- ceruminal gland hyperplasia or hypertrophy
- Lumen stenosis
- Calcification
