Lecture 19 4/8/25

Question 1

What are the characteristics of the pinna?

Answer 1

-auricular cartilage covered on both sides by skin
-localizes and collects sound waves for transmission to tympanic membrane

Question 2

What is the importance of the intertragic incisure?

Answer 2

this structure is where ear medications need to go

Question 3

What is the typical anatomy of the external ear canal?

Answer 3

-about 5 to 10 cm long and 4 to 5 mm wide in dogs
-vertical canal is formed from auricular cartilage and runs ventrally and slightly rostrally
-horizontal canal is formed from annular cartilage, is shorter, and runs medially

Question 4

What are the characteristics of the tympanic membrane?

Answer 4

-thin, slightly opaque membranous partition
-separates external ear from middle ear

Question 5

What are the characteristics of the pars flaccida portion of the tympanic membrane?

Answer 5

-smaller air-filled upper portion
-flaccid, rich blood supply
-heals rapidly

Question 6

What are the characteristics of the pars tensa portion of the tympanic membrane?

Answer 6

-larger lower portion
-thin, tough, and pearl gray

Question 7

What are the characteristics of the stria mallearis?

Answer 7

-manubrium of the malleus that is visible
-points in the direction of the dog’s nose

Question 8

How do cats and dogs differ in terms of most common ear condition?

Answer 8

-dogs tend to get otitis externa
-cats more commonly have middle ear conditions

Question 9

What are the characteristics of external ear canal histology?

Answer 9

-extension of skin; diseases that affect skin can affect ear canal
-stratified squamous epithelial cells
-sebaceous glands
-fewer ceruminous glands than sebaceous glands

Question 10

What are the characteristics of cerumen/ear wax?

Answer 10

-combination of desquamated epithelial cells and secretions from sebaceous and ceruminous glands
-traps foreign material
-possibly antibacterial
-keeps tympanic membrane moist and pliable

Question 11

What is the purpose of epithelial migration?

Answer 11

self-cleaning mechanism for the ear canals

Question 12

What are the characteristics of the healthy ear canal environment?

Answer 12

-consistent temperature and humidity
-low numbers of yeast and gram+ cocci is normal

Question 13

What are the primary causes of otitis externa that create otic inflammation?

Answer 13

-parasites
-hypersensitivity disorders
-foreign bodies
-keratinization disorders
-neoplasms
-autoimmune diseases

Question 14

What are the characteristics of atopic dermatitis?

Answer 14

greater than 50% have otitis
-less than 5% have otitis as the only clinical sign
-allergic skin diseases are the most common cause for recurrent otitis

Question 15

What are the characteristics of food allergy?

Answer 15

-50 to 80% have otitis externa
-otitis is the only clinical signs in about 20 to 25% of patients

Question 16

What are the possible foreign bodies in the ear?

Answer 16

-grass awns/seeds
-concretions of medications
-hair
-dirt
-sand
-dead insects

Question 17

What are the predisposing factors that increase the risk of developing otitis by changing the ear microenvironment?

Answer 17

-conformation
-excessive moisture
-incorrect/over-cleaning
-systemic diseases
-obstruction of the ear canal

Question 18

What are the possible conformations that can predispose to otitis?

Answer 18

-pendulous pinnae
-excessive ceruminous glands
-stenotic ear canals
-hairy ear canals

Question 19

What are the perpetuating factors that occur secondarily and can make otitis worse?

Answer 19

-infectious organisms
-otitis media
-chronic pathologic changes
-treatment errors

Question 20

Which yeast species is most commonly found in otitis cases?

Answer 20

Malassezia pachydermatis

Question 21

Which bacteria species can be found in otitis cases?

Answer 21

-Staphylococcus sp. (most common)
-Proteus sp.
-Corynebacterium sp.
-E. coli
-Pseudomonas sp.

Question 22

What are the clinical signs of acute otitis externa?

Answer 22

-head shaking
-abnormal ear carriage
-pain/pruritus
-erythema
-aural hematoma
-odor

Question 23

What are the clinical signs of chronic otitis externa?

Answer 23

-lichenification of medial pinna
-thickened and less pliable cartilage
-canal stenosis/calcification
-odor

Question 24

What are the key questions to ask when getting a history in an otitis case?

Answer 24

-recurrent vs seasonal
-history or evidence of other skin dz
-pruritic vs non-pruritic
-swimming or bathing history
-previous treatments and efficacy
-ability to treat and clean pet’s ears

Question 25

What are the important things to do when assessing a pet for otitis?

Answer 25

-complete physical exam -examine oral cavity/look for pain with opening mouth -look for neurologic deficits -otic examination

Question 26

What should be assessed when doing an otoscopic exam?

Answer 26

-tympanic membrane intact vs ruptured -stenosis -proliferation -type of exudate

Question 27

What should be looked for when doing an ear cytology?

Answer 27

-bacteria -yeast -inflammatory cells

Question 28

What are the indications for culture and susceptibility testing in otitis cases?

Answer 28

-rod bacteria on cytology -infection that persists despite treatment -neutrophils seen without bacteria

Question 29

What is the most common technique for ear cleaning?

Answer 29

squirting a small amount of cleaner into the ears, massaging to break up debris, and using a cotton ball to remove debris until clean

Question 30

What is the prognosis for otitis?

Answer 30

-depends on secondary changes -if ear canals cannot be opened medically, prognosis for medical management is guarded

Question 31

What are the keys to success when treating otitis?

Answer 31

-open up the ear canal -clean the canal and middle ear -use large volumes of topical medication -use solutions rather than ointments, esp. if stenotic -do frequent follow up exams -have owners do a maintenance regimen, esp. in allergic dogs -identify and address underlying cause when possible