Otitis 1 Flashcards
What is otitis?
- Inflammation of the ear canal
- Otitis externa = external ear canal
- Otitis media = middle ear
- Otitis interna = inner ear
What is histology of the ear?
- Ear canal lined by modified skin =
– Small hairs
– Ceruminous glands
– Sebaceous glands - Middle ear lined by modified respiratory epithelium =
– Simple squamous to cuboidal
– Few ciliated cells
– Mucous-secreting goblet cells
What is the self-cleaning mechanism of the outer ear?
- Cerumen =
- Sebaceous & ceruminous gland secretions
- Catches foreign material, desquamated keratinocytes & microbes
- Contains antimicrobial peptides and Igs
- Epithelial migration = Living keratinocytes carry cerumen and contents out of canal
What is the self-cleaning mechanism of the middle ear?
- Mucous from goblet cells traps microbes and cellular debris
- Eustachian tube =
– Drains mucous from middle ear cavity into nasopharynx
– Equalises air pressure either side tympanic membrane
What is normal flora of the external ear canal?
- Gram +ve cocci predominate = – Staphylococcus pseudintermedius, S.schleiferi
- Coagulase –ve staphylococci
- Streptococcus spp.
- Micrococcus spp.
- Malassezia spp.
What are primary causes of otitis?
- VIP MEGA FAME
- Viral = FCV, FHV, distemper
- Immune mediated = vasculitis, EM
- Parasites = otodectes, demodex, ticks
- Mycoses = aspergillus
- Endocrine = hypothyroidism
- Glandular disorders = sebaceous gland hyper/hypoplasia
- Allergy = AD, AFR, contact allergy
- Foreign body = foxtail, hair, sand
- Autoimmune = PF, LE
- Miscellaneous = auricular chondritis
- Epithelialisation disorders = primary seborrhea
What ate the main primary causes of otitis in dogs?
- FAB
- Foreign bodies
- Allergic skin disease
- Bugs
What ate the main primary causes of otitis in cats?
- FAB
- Flu
- Allergic skin disease
- Bugs
What is seen with hypersensitivity otitis?
- Otitis externa common allergic disease
- Pruritic
- Dog meets Favrot’s criteria = Onset of signs less than 3 years,
-Dog living mostly indoors
-Glucocorticoid-responsive pruritus
-Pruritus sine materia at onset (alesional pruritus, ‘itch before rash’)
-Affected front paws
What is seen with foreign body otitis?
- Unilateral otitis
- Grass seeds most common - late spring to end of summer
- Can be hidden in wax
- Painful
What is seen with otodectes cynotis?
- Common cause of otitis
- Dark ‘coffee ground’ wax, small white mites
- Most patients have HyperSensitivty Reaction to mites > intense pruritus
- Ectopic disease (mites leave ear and affect haired skin e.g. tail tip in cats)
- Mites photophobic so if not seen otoscopically sample ear (indirect smear in paraffin)
What are most common secondary causes?
- Microbial infection (most common) =
– Gram +ve cocci (Staphylococci, Streptococci)
– Gram -ve rods (Pseudomonas, Proteus, E. coli)
– Yeast (Malassezia pachydermatis) - Topical medication reaction =
– Irritation of inflamed skin by alcohol, acid, propylene glycol - Inappropriate cleaning =
– Physical trauma, excessive moisture and maceration
What are predisposing factors of otitis?
- Obstructive ear disease = Neoplasia and polyps
- Conformation =
-Hairy canals (e.g. poodle)
-Narrow canals (e.g. Shar pei)
-Waxy canals and hairy pinnae (cocker spaniel)
-Pendulous pinnae (e.g. bloodhound) - Environment =
-Water (swimming, groomers, cleaners)
-High temperature and humidity - Systemic disease = Immune suppression, debilitation
What are perpetuating factors?
Perpetuating = results from inflammation, prevent resolution
* Progressive pathological change = chronic inflammation of soft + bony tissues due to primary / secondary causes
* otitis media - extension of OE, rupture of TM
What occurs with progressive pathological change of the ear canal?
- Failure of epithelial migration
- Progressive epithelial hyperplasia, oedema, fibrosis & folding
- Glandular dilation and hyperplasia
- Canal stenosis
- Rupture of tympanum
- Calcification of pericartilaginous tissue
- Osteomyelitis
- Para-aural abscessation
