Ear

Question 1

What are the 3 functions of the ear?

Answer 1

1. collect auditory stimuli
2. transduce mechanical stimuli
3. transmit nerve impulses to the CNS

Question 2

Ear anatomy:

Answer 2

Question 3

What are the 4 major components of the external ear? What is its function?

Answer 3

1. haired skin
2. auricle/pinna of elastic cartilage
3. external ear canal/auditory meatus
4. tympanic membrane (eardrum)

collect and convey sound waves

Question 4

External ear, histology:

Answer 4

Question 5

What are ceruminous glands? What do they secrete?

Answer 5

simple, coiled tubular apocrine glands located within the skin of the external acoustic canal

ear wax (cerumen) - mixture of viscous secretions from sebaceous glands, sloughed skin cells and less viscous ones from modified apocrine sweat glands (ceruminous glands)

Question 6

What is commonly sampled for external ear disease? What are 7 common diagnostics used?

Answer 6

pinna and wall of the canal

1. otoscopic examination
2. cytology (impression smears, tape preparations, swab)
3. superficial and deep skin scrapings
4. trichograms
5. bacterial and fungal culture and sensitivity
6. FNA
7. biopsy

Question 7

External ear cytology:

Answer 7

swab

Question 8

What is the main cause of otitis externa? In what animals is it most common?

Answer 8

rarely primary —> interaction of predisposing factors, primary causes, and secondary causes

dogs > cats

Question 9

What are the most common clinical signs of otitis externa? What signs are associated with chronic cases?

Answer 9

• exudate
• hemorrhage
• auricles tend to be red, warm, edematous, and painful

CHRONIC = thickened epidermis, stiff external ear canal due to cartilage ossification, stenosis due to skin proliferation

Question 10

What can happen if otitis externa is left untreated?

Answer 10

surgical removal of the ear canals are necessary

Question 11

What are the 6 most common types of predisposing factors leading to otitis externa?

Answer 11

1. conformation - stenotic external acoustic meatus, excess hair, pendulous pinnae
2. excessive moisture - swimmer’s ear, high humidity
3. excessive cerumen production - overactive glands
4. treatment effects - trauma from treatment swabs, irritation from topicals, altered microflora
5. obstructive ear disease - neoplasm, polyps, granulomas
6. systemic disease - viral disease, debilitation, catabolic states, immunosuppression

Question 12

What are the 6 most common types of primary causes of otitis externa?

Answer 12

1. parasites - ticks, mites, nematodes
2. hypersensitivity - atopic dermatitis, food, contact, drug reactions
3. keratinization - primary idiopathic seborrhea, endocrine disorders, sex hormone disorders, lipid-related conditions
4. foreign bodies - plants (foxtails), hair, sand, dirt, hardened secretions, medications
5. glandular disorders - ceruminous/sebaceous hyperplasia, altered type and rate of secretion
6. autoimmune - lupus erythematosus, pemphigus foliaceous/vulgaris/erythematosus
7. vascular disease - cold agglutinin disease, solar dermatitis, frostbite, vasculitis, juvenile cellulitis, aural chonritis

Question 13

What are 2 types of secondary causes of otitis externa?

Answer 13

1. bacteria - Staphylococcus, Proteus, Pseudomonas, E. coli, Klebsiella
2. yeast - Malassezia, Candida albicans

Question 14

How does acute, chronic, and end-stage otitis externa compare?

Answer 14

ACUTE = diffusely red, increased pale yellow/brown exudate

CHRONIC = seems bumpy, hyperplastic

END-STAGE = stenosis, can’t see external ear canal due to hyperplastic cells and cartilage ossification

Question 15

What is auricular acariasis? What is the most common cause in dogs and cats? In what animals is it most common?

Answer 15

ear mite infestations —> Otodectes cynotis

young, free-roaming cats and dogs with outdoor access

Question 16

What are the main clinical signs of auricular acariasis? How is it diagnosed?

Answer 16

• pruritis
• head shaking
• head tilt
• circling
• dark “coffee ground” otic discharge

otoscopic examination and microscopic examination of samples from the ear

Question 17

Auricular acarsiasis, otoscopic examination:

Answer 17

ear mite infestation

coffee ground discharge + light/pale brown mites

Question 18

Otodectes cynotis infestation, cat:

Answer 18

Question 19

What is the most common cause of auricular acariasis in rabbits?

Answer 19

Psoroptes cuniculi

• crust within canal

Question 20

What is the cause of aural plaques? What is the major clinical finding?

Answer 20

horses > 1 y/o infected with Equus caballus papillomavirus

raise, well-demarcated, hypopigmented. hyperkeratotic plaques arising from the concave surface of the auricle

Question 21

What is the cause of canine leproid granulomas? In what dogs is it most common?

Answer 21

novel mycobacterial species

Boxers

Question 22

What gross finding is associated with canine leproid granuloma? Histological lesion?

Answer 22

single to multiple well-circumscribed, firm, nonpainful dermal nodules on the pinnae

pyogranulomatous dermatitis with intralesional acid-fats positive bacteria

Question 23

Where is ischemic dermatopathy most commonly found? What are 50% of cases associated with? In what dogs is this most common?

Answer 23

vaccine sites, pinna, periocular/face, distal extremities

vaccination (rabies)

• Toy/Miniature Poodles
• Chihuahuas
• Maltese
• Yorkshire Terriers
• Jack Russel Terriers

Question 24

What lesion is associated with ischemic dermopathy?

Answer 24

• alopecia, crusts, scales, erythema, erosions/ulcers, hyperpigmentation
• scalloped and notched ear margin due to poor blood supply

Question 25

In what dog is localized parakeratotic hyperkeratosis most common? How does it present grossly? What may help improve these cases?

Answer 25

young Boston Terriers and French Bulldogs (3.5 months) mild to severe parakeratotic hyperkeratosis of the pinna margins oral zinc supplementation

Question 26

What are folded ear tips associated with in cats?

Answer 26

long-term glucocorticoid therapy ---> suspected interaction with cartilage

Question 27

In what animals are aural hematomas most common? What is a major risk factor?

Answer 27

dogs (large-breed, Golden Retrievers, Labrador Retrievers), pigs, cats ongoing ear disease causes excessive head shaking

Question 28

What is the pathogenesis of the development of aural hematomas?

Answer 28

- chronic external or middle ear disease causes the animal to continuously and vigorously shake their heads - this causes trauma to blood vessels and auricular cartilage ad the sides and tips of the auricles

Question 29

In what cats is feline ceruminous cystomatosis most common? What lesion is associated? How is it diagnosed?

Answer 29

older, male Abyssinians and Persians multiple small nodules or vesicles that are dark brown, blue, or black on the ear canal, eyelids, lips, or inner pinnae/outer ear canal biopsy

Question 30

What causes aural squamous cell carcinomas?

Answer 30

UV light on non-pigmented skin

Question 31

How do the 2 types of ceruminous gland neoplasias compare?

Answer 31

1. ADENOMA - single to multiple, small, pedunculated, irregular and firm masses 2. ADENOCARCINOMA - locally invasive, 50% metastasize to regional LNs, lungs, and visceral organs

Question 32

Where is the middle ear located? What nerve is particularly associated?

Answer 32

within the tympanic bulla facial nerve (CN VII) ---> damage/infection can lead to facial paralysis

Question 33

What are the 4 major components of the middle ear? What is its function?

Answer 33

1. tympanic membrane (ear drum) 2. tympanic cavity 3. auditory ossicles - malleolus, incus, stapes 4. Eustachian tube vibration of sound on the tympanic membrane is transmitted through the middle ear to the cochlea (inner ear) via the ossicles

Question 34

What 3 diagnostics are used for middle ear disease?

Answer 34

1. otoscopic examination 2. cytology 3. bacterial and fungal culture and sensitivity

Question 35

What does the normal tympanic membrane look like? What happens with otitis media?

Answer 35

translucent, no redness opaque and erythematous

Question 36

In what animals is otitis media most common? What is the cause?

Answer 36

ruminants, pigs nasopharyngeal ascent of bacteria through the Eustachian tube

Question 37

What are the specific etiologies of otitis media in pigs and ruminants?

Answer 37

PIGS - Pasteurella multocida, Trueperella pyogenes, Mycoplasma hyorhinis RUMINANTS - Histophilus somni, P. multocida, T. pyogenes, Mycoplasma bovis, Streptococcus spp.

Question 38

What gross findings are seen with acute otitis media? Chronic?

Answer 38

fibrinopurulent to caseous exudate in the bulla bones remodeling, fibrosis, granulation tissue

Question 39

In what animals are aural inflammatory polyps most common? Where does it typically originate? Where does it tend to move?

Answer 39

nasopharynx of young cats (< 2 y/o) middle ear mucoperiosteum, Eustachean tube mucosa, or external ear dermis can evert through the Eustachian tube into the nasopharynx or perforate the tympanic membrane (aural)

Question 40

What clinical signs are associated with aural inflammatory polyps?

Answer 40

(depends on location) - otitis externa, otitis media - extension into oropharynx leads to nasal, otic, or ocular discharge, causing sneezing, dyspnea, stridor, voice changes, dysphagia, head tilts, Horner's syndrome, nystagmus, or ataxia

Question 41

What are the 2 major components of the inner ear? What nerve is closely associated?

Answer 41

1. cochlea - organ of hearing 2. vestibular system - organ of balance vestibulocochlear nerve (CN VIII) ---> otitis interna can cause Horner's syndrome

Question 42

What are the 3 components of the vestibular apparatus? What structures are found within?

Answer 42

1. utricle 2. saccule 3. semicircular ducts specialized structures containing neuroepithelial cells (sensory cells) - macula utriculi, macula sacculi, crista ampullaris

Question 43

What are the 4 major components of the cochlea?

Answer 43

1. tectorial membrane - vibrated by sound wave energy 2. organ of Corti - transduce sound vibrations into neural signs (hair cells) 3. basilar membrane - vibrated by sound wave energy 4. stria vascularis - produces endolymph

Question 44

In what animals is hereditary deafness most common? What 2 other pathologies is it associated with?

Answer 44

animals with white pigmentation - dogs with piebald or merle genes, blue-eyed white cats 1. hypopigmentation 2. stria vascularis dysfunction

Question 45

What are the 2 types of vestibular disease of the internal ear?

Answer 45

1. CENTRAL - dysfunction of brainstem or cerebellum 2. PERIPHERAL - dysfunction of vestibular nerve (VIII) or internal ear, commonly due to otitis media or otitis interna

Question 46

What are the most common signs of vestibular disease of the internal ear?

Answer 46

- head tilt - circling - ataxia - nystagmus - +/- Horner's syndrome

Question 47

What are the components of Horner's syndrome?

Answer 47

- constricted pupils - elevated third eyelid - sinking of the eyeball into the body cavity - drooping of the upper eyelid