Otitis 1

Question 1

What is otitis?

Answer 1

• Inflammation of the ear canal
• Otitis externa = external ear canal
• Otitis media = middle ear
• Otitis interna = inner ear

Question 2

What is histology of the ear?

Answer 2

• 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

Question 3

What is the self-cleaning mechanism of the outer ear?

Answer 3

• 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

Question 4

What is the self-cleaning mechanism of the middle ear?

Answer 4

• 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

Question 5

What is normal flora of the external ear canal?

Answer 5

• Gram +ve cocci predominate = – Staphylococcus pseudintermedius, S.schleiferi
• Coagulase –ve staphylococci
• Streptococcus spp.
• Micrococcus spp.
• Malassezia spp.

Question 6

What are primary causes of otitis?

Answer 6

• 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

Question 7

What ate the main primary causes of otitis in dogs?

Answer 7

• FAB
• Foreign bodies
• Allergic skin disease
• Bugs

Question 8

What ate the main primary causes of otitis in cats?

Answer 8

• FAB
• Flu
• Allergic skin disease
• Bugs

Question 9

What is seen with hypersensitivity otitis?

Answer 9

• 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

Question 10

What is seen with foreign body otitis?

Answer 10

• Unilateral otitis
• Grass seeds most common - late spring to end of summer
• Can be hidden in wax
• Painful

Question 11

What is seen with otodectes cynotis?

Answer 11

• 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)

Question 12

What are most common secondary causes?

Answer 12

• 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

Question 13

What are predisposing factors of otitis?

Answer 13

• 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

Question 14

What are perpetuating factors?

Answer 14

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

Question 15

What occurs with progressive pathological change of the ear canal?

Answer 15

• 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

Question 16

What is your plan with otitis?

Answer 16

1. History, physical exam + diagnostic investigations
2. ID causes + factors for individual
3. Prognosis, management plan + Medical vs surgical

Question 17

How would you perform an ear exam?

Answer 17

• Always check both ears!
• Assess and palpate (gently) = Pinnae, External ear canals (non-painful, pliable, moveable)
• Otoscopy
  – Need VN/owner to restrain animal
  – Not possible if painful (sedation/GA or treat and recheck)
  – Strong light, small cone to reduce contact with epithelium
  – Gently pull pinna to straighten EEC
  – Epithelium should be pale and smooth, little wax, canal open (stenotic breeds Shar Pei, FBD, Pug)

Question 18

What are clinical signs of otitis externa?

Answer 18

• Otic pruritus = scratching, rubbing, headshaking
• Pain
• Discharge (otorrhea), malodour
• Loss of hearing
• Pinnal changes = erythema, lichenification, scaling, pyotraumatic dermatitis, aural haematoma
• Otoscopy = epithelial erythema, hyperplasia, erosion/ulceration, fibrosis, stenosis of External Ear Canal

Question 19

What is the progression of clinical signs?

Answer 19

• Secondary causes and perpetuating factors develop
  due to primary cause =
  1. Allergic otitis > initial Malassezia overgrowth > staphylococci overgrowth or infection
  2. Change in EEC environment due to inflammatory change
  (PPC) and increased humidity
  3. Overgrowth and infection with transient Gram –ve rods
  (usually Pseudomonas)
• Most cases present when secondary causes arrive
• Chronic Pseudomonas OE commonly progresses to
  OM in dogs (less commonly OI)

Question 20

What diagnostic imaging can be used?

Answer 20

• Assess severity of progressive pathological changes (PPC) in external ear canal
• # Presence of OM + OI
• Radiography
• CT - best
• MRI

Question 21

What are indications for myringotomy?
(incision into eardrum to relieve pressure / drain fluid)

Answer 21

• Bulging eardrum on otoscopy with pain or neurological signs
  – Horner’s syndrome, vestibular disease, facial paresis
• Radiographic/CT/MRI bulla changes and intact eardrum
• Evidence of fluid/tissue behind eardrum (requires experience of assessing eardrum)
• Medically unresponsive vestibular disease with an intact eardrum

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