Lecture 38: Special Senses (Ear)

Question 1

How is sound senses by the ear?

Answer 1

sound waves virbrate on the tympanic membrane

it moves the malleus - incus - stapes

vibrates on the cochlear window

create fluid waves in the perilymph

spiral wave transforms wave in to nerve impulse

cochlear nerve goes to brainstem which goes to auditory cortex

Question 2

Define otitis

Answer 2

inflammation of the ear

there is extera, media, and interna

Question 3

What is cerumen? Where does it come from?

Answer 3

earwax

made from specialized sweat glands - ceruminous glands

Question 4

List 2 main portals of entry to the external ear?

Answer 4

extension from the environment or the middle ear

hematogenous

Question 5

What animal is otitis externa common in? List 2 common causative agents?

Answer 5

dogs

primary causes
- ectoparasite
- FB
- generalized skin conditions

secondary
- bacteria = Pseudomonas
- fungi = malassezia

Question 6

List 3 predisposing factors to developing otitis externa

Answer 6

breed

conformation

external ear moisture

Question 7

What are the sequelae of chronic otitis external

Answer 7

thickening and roughening of epidermis

stiff auricular cartilage due to fibrosis and osseus metaplasia

increased proliferation of ceruminous glands

stenosis of the ear canal
- reducing hearing
- causing recurrent inflammation

Question 8

What causes ear tip necrosis

Answer 8

infarction due to …
- frostbite
- bacterial septicemia
- toxins (ergot)
- virus (FIP)
- hypersensitivity

Question 9

What causes aural hematomas?

Answer 9

chronic otitis externa or media leading to head shaking and ear trauma which damages the blood vessels in the pinna

Question 10

What animals are aural hematomas most common in? What are the clinical and gross signs

Answer 10

dog, cat, pig

pain

heal by fibrosis causing thickening and malformation

Question 11

List 3 examples of mites and their associated hosts

Answer 11

mites = otoacariasis

otodectes cyanotis = dog/cat

notodectes cati = cat/rabbit

psoroptes cuniculi = goat/sheep/horse

Question 12

List 1 main tick affecting the external ear

Answer 12

spinose ear ticks

Question 13

What are aural plaques and what animals do they affect?

Answer 13

horses >1yo

they are aural papillomatoses

Question 14

What causes aural plaques? What do they look like? How are they transmitted?

Answer 14

equine papillomavirus transmitted by biting flies

pale/raised/hyperkeratotic plaques and warts
- decreases the cosmetic value but not super significant

Question 15

List 5 types of neoplasia that can affect the external ear

Answer 15

SCC

sebaceous adenoma

mast cell tumor

trichoblastoma

ceruminous gland tumor

Question 16

What is a ceruminous gland tumor?

Answer 16

benign hyperplasia/adenoma
in external auditory meatus

can become locally invasive ceruminous adenocarcinoma

cats

Question 17

What type of epithelium lines the middle ear?

Answer 17

cuboidal epithelium +/- cilia

Question 18

What are the 3 main bones of the middle ear?

Answer 18

incus
malleus
stapes

Question 19

What part of the ear is the tympanic bullae part of?

Answer 19

middle ear

Question 20

List 3 portals of entry into the middle ear

Answer 20

direct extension from the external ear

tympanic membrane

auditory tube (connecting to the oropharynx)

Question 21

What animals is otitis media common in? What are the common causative agents?

Answer 21

ruminant and pig

major respiratory pathogens
- pigs = P. multocida
- ruminant = H. somni/P/ multocida/T. pyogenes

Question 22

What are the clinical signs of otitis media

Answer 22

drooping ear
facial paralysis
head tilt
nasal discharge
respiratory signs (if concurrent with respiratory disease)

can cause osteolysis of surrounding bone

Question 23

What is horners syndrome? What animals is it most common in?

Answer 23

reduced SNS innervation
- the post ganglionic SNS fibres run near the internal carotid by the middle ear = often secondary to otitis media

cat and dog

Question 24

What are the clinical signs of horners syndrome

Answer 24

endopthalmitis
miosis
narrow palpebral rupture
3rd eyelid protrusion
peripheral vasodilation

Question 25

What animals are nasopharyngeal polyps common in? Where do they usually occur?

Answer 25

cats <2 yo from the mucosa of the middle ear or auditory tube

Question 26

What are the gross and clinical signs of nasopharyngeal polyps

Answer 26

gross = protruding/pedunculated smooth and shiny mass clinically - otitis external or media - discharge from nose/eye - voice change - head tilt - horners - severe dyspnea

Question 27

What is the causative agent of guttoral pouch disease? What is a common secondary invader?

Answer 27

strep equi equi fungal infection via aspergillus

Question 28

What are the clinical signs of guttoral pouch disease

Answer 28

epistaxis dysphagia laryngeal hemiplasia horners syndrome facial nerve paralysis

Question 29

What are chondroids

Answer 29

hardened pus that can be a source of infection associated with guttoral pouch mycosis

Question 30

What is temporohyoid osteoarthropathy? What animal does it affect?

Answer 30

equids of all ages It is degeneration (bony proliferation and anklysosi) of synchondroses joints (stylohyoid/petrous temporal bone)

Question 31

What are the clinical signs of temporohyoid osteoarthropathy

Answer 31

abnormal head behaviour - ear rubbing - abnormal chewing - resisting the bit joint fracture leading to vestibular signs or facial nerve paralysis

Question 32

What are the 5 main causes of temporohyoid osteoarthropathy

Answer 32

otitis media/interna hematogenous spread resp infection guttoral pouch disease DJD

Question 33

How is temporohyoid osteoarthropathy diagnosed

Answer 33

imaging and endoscopy

Question 34

What are the 2 main portals of entry to the inner ear

Answer 34

extension from the middle ear or brain/nerves hematogenous

Question 35

What is another name for otitis interna

Answer 35

labrythitis

Question 36

What is affected during peripheral vestibular disease

Answer 36

internal ear sensory receptors like vestibular ganglia and the axons of the vestibularcochlear nerve (CN8)

Question 37

What is affected during central vestibular disease

Answer 37

brainstem and cerebellum

Question 38

What are the clinical signs of vestibular disease

Answer 38

nystagmus head tilt facial paralysis circling asymmetric ataxia

Question 39

What are the common causes of vestibular disease

Answer 39

otitis interna - virus (FIP)/bacteria/protozoa/fungi inner ear tumor idiopathic ototoxic drugs - damage hairs causing deafness - aminoglycosides/furosemide/platinum chemotherapeutics

Question 40

What is old dog vestibular disease

Answer 40

geratric dogs acute onset resolve spontaneously idiopathic