Ears - NAVDF 2019

Question 1

T/F: There is no subcutaneous tissue in the ear canal.

Answer 1

True - the dermis is attached to connective tissue, which is connected to the cartilage

Question 2

What are the two cartilage components of the external ear canal?

Answer 2

auricular cartilage (makes up the pinnae, vertical canal and part of the horizontal canal) and annular cartilage

Question 3

What is the external acoustic meatus?

Answer 3

distal end of the horizontal canal - part is covered by annular cartilage, the remainder is bone with skin directly overlying

Question 4

Where is the pars tensa in relation to the external acoustic meatus?

Answer 4

medial ring of the acoustic meatus

Question 5

What are the components of cerumen?

Answer 5

exfoliating corneocytes, intercellular material (e.g. triglycerides, sterol esters, fatty acid esters, squalene), and glandular secretions

Question 6

What are the components of the middle ear?

Answer 6

tympanic cavity and walls, medial wall of tympanic membrane, auditory ossicles and associated ligaments, muscles, nerves (chorda tympani and other smaller nerves) and the auditory tube

Question 7

Why is the ventrolateral quadrant of the pars tensa the preferred site for myringotomy?

Answer 7

the portion of the pars tensa by the manubrium of the malleus has the germinative epithelium (so want to avoid damaging this tissue)

Question 8

What are the components of the tympanic cavity?

Answer 8

dorsal - cochlear promontory, cochlear window; ventral - tympanic bulla (largest portion); middle - septum bulla

Question 9

Why are cats more prone to Horner’s syndrome with otitis media?

Answer 9

plexus of nerve fibers from the cranial cervical ganglion are present in the middle ear of the cat (damage => Horner’s sydnrome)

Question 10

What is biofilm?

Answer 10

matrix of polysaccharides, DNA, proteins –> form an extracellular polymeric substance

Question 11

T/F: Sterile cultures can have biofilm.

Answer 11

TRUE

Question 12

What is most diagnostic on cytology for presence of otitis externa?

Answer 12

inflammatory cells

Question 13

What is the published prevalence of otitis externa in dogs?

Answer 13

10-15%

Question 14

What structure can interfere with examination of the deep ear canal?

Answer 14

auricular projection (Noxonian fold =D)

Question 15

Added evidence a bacterial aggregate is biofilm is obtained when what stain is positive for the amorphous material around the organisms?

Answer 15

PAS stain

Question 16

What organisms isolated from canine otitis externa have been shown capable of forming biofilms in vitro?

Answer 16

Malassezia, Pseudomonas, and Staphylococcus

Question 17

What is the best method for assessing proliferative changes in the ear canal?

Answer 17

otoscopic examination