123. Middle_Inner ear

Question 1

middle ear components

Answer 1

–tympanic cavity (3 compartments in dog, 2 cat)–tympanic membrane–auditory tube–nerves –ossicles connect tympanic membrane to inner ear (malleus, incus, stapes) and concentrate sound waves to inner ear fluid environment

Question 2

tympanic cavity compartments in dog vs cat

Answer 2

dog 3–dorsal–epitympanum (smallest)–middle–mesotympanum–ventral–hypotympanum (largest)cat 2–rostrolateral (epi and mesotympanum–small)–ventral (hypotympanum–large)thin boney shelf separates –promontory bone is more prominent and exposed in cats than dogs (more prone to neuro damage/deficits)lining = contiguous with respiratory (nasopharyngeal) epith via auditory tube (cubodial/ciliated/some squamous cells)

Question 3

inner ear components

Answer 3

vestibulecochleasemicircular canalsall contain fluid (endolymph) and receive concentrated sound waves from external ear thru the middle ear via ossiclesinnervated by vestibulocochlear nerve VIIIfx: sound perception and balance

Question 4

3 ways bacT get into the ear

Answer 4

1. external ear canal/external auditory meatus**2. nasopharynx via auditory tube3. hematogenousothers: FB, bites, para-aural abscess

Question 5

most common organisms in middle ear

Answer 5

staph intermediuspseudomonasmalessezia

Question 6

middle ear polyps

Answer 6

sterile, inflammatory, non neoplasticyoung cats +/- viral infectionsoriginate from epith of tympanum or auditory tubecan go into nasopharynx, tympanic cavity, or out external ear canaltx traction (recur 10-50%)Tx VBO cats—LBO/TECA dogs

Question 7

cholesteatomas

Answer 7

destructive, expanding keratinized squamous epith +/- infection +/- metaplasiabrachycephalic breedsRO neoplasiaTX: lateral or ventral BOprognosis guarded, recurrence occurs

Question 8

primary secretory otitis media

Answer 8

cavalier king charles spanielsaccumulate mucinous material within tympanic cavity suspect congenital dysfunction of drainage of the auditory tube

Question 9

cause of sterile otitis media

Answer 9

ciliary dyskinesis (congenital)

Question 10

changes to the tympanic membrane that can be seen on otoscopy and lead to suspicious middle ear dz

Answer 10

–buldging–rupture–change of color–thickening/loss of transparencymay need myringotomy for cultures, cytology, biopsy if indicated

Question 11

what does BAER stand for

Answer 11

brainstemauditoryevokedresponsehearing test (screen dalmatians)other test is impedance audiometry

Question 12

name of tube for tympanostomy drainage

Answer 12

myringotomy, lavage (culture, histopath)Reuter Bobbin vent tube

Question 13

T/Fdespite risks of ototoxicity with systemic use, topical amino glycosides (gentamicin) in the middle ear does not result in ototoxic concentrations in the vestibular apparatus

Answer 13

TRUE

Question 14

complications following VBO in cats

Answer 14

hornersvestibular