Otitis Flashcards
define otitis externa
- inflammation and/or infection of the ear canal (ends at the intact ear drum)
- VERY common in dogs
-less common in other species - can be a consequence of any of the primary factors
-cAD!!
-parasites
-foreign bodies
-neoplasia/polyps
-endocrinopathies
-autoimmune/immune mediated diseases
-keratinization disorders - most of the primary factors induce local inflammation but
-endocrinopathies and some tumors/growths cause microbiome shifts by negatively influencing the skin immune system as well (sneakier)
what are the symptoms of otitis externa
- head shaking, scratching, pawing
- sensitivity, pain
- erythema of ear canal and skin around ear canal opening
- tissue swelling
- otic discharge
- malodor
- conductive hearing deficiency/hearing loss
-ears so full of gunk or swollen that sounds can’t get through = conductive hearing deficiency
*symptoms may be unilateral or bilateral
how do we decide how to treat otitis externa?
by addressing every factor involved with the specific patient
- PE, otoscopy, check for microbes via ear cytology
-most common isolated:
–staph pseudintermedius (cocci)
–pseudomonas aeruginosa (rods)
–malassezia pachydermatitis (yeast)
–over time can find weird things like E. coli (secondary to antimicrobial treatment allowing overgrowth of weird bugs) - check for parasites on unstained ear smears
-otodectes cynotis
-demodex spp.
-trombicula spp. (chigger)
describe otitis externa treatment
MANY topical treatment options as long as patient’s tympanum is intact
basic building blocks of medicated ear drops:
1. antiparasitic if needed: thiabendazole, pyrethrin
2. antibiotic: gentamicin, neomycin, orbifloxacin, florfenicol, polymyxin B
3. antifungal: clotrimazole, miconazole, ketoconazole, nystatin
4. anti-inflammatory/steroid: prednisolone, hydrocortisone, dexamethasone, mometasone
usually antibiotic + antifungal + anti-inflammatory, then search for anti-parasitic if needed
-anti-inflammatory helps bring inflammation down but could recur once stop medication! (treating in a reactive way at this point)
application frequency is variable and depends on the product: twice daily, once daily or one-time treatment (otipacks)
describe the safety of different antibiotics for the ear
- gentamicin: in SO many ear drops because is SO effective topically, kills almost everything in its path but is potentially ototoxic so should ONLY be used in patients with INTACT tympanic membranes!!!
- enrofloxacin or orbifloxacin (fluoroquinolones)
-NOT labelled as safe in case of rupture tympanic membranes either - there are 2 human ear medications containing ciprofloxacin and ofloxacin labelled for use in middle ears/ruptured tympanic membrane situations
but is hard to examine painful patient eardrums so when in doubt regarding tympanic membrane status, topical fluoroquinolones are likely safer than gentamicin!
how long do we treat for otitis externa?
depends!!
- type of infection: biofilm, resistant bacteria
- severity of infection
- severity of inflammation
- aggravating factors: fibrosis, stenosis, hyperplastic tissue, masses
basically treat until recheck! because only the vet can determine whether inflammation and infection have really resolved
how do we proactively treat otitis externa (if owner not interested in allergy diagnostics)?
- control ear canal inflammation to keep microbiome from shifting from healthy to infection
- topical steroids in addition to oral oclacitinib
-hydrocortisone: weak, can only use in mild cases but if used 1-2x/week can help prevent more advanced cases (for intact eardrum)
-mometasone furoate, flucinolone acetonide, betamethasone diproprionate: prescription, high potency! (for intact eardrum)
-dexamethason SP: injectable, but can be used plain as a topical (appears safe in ruptured tympanic membranes); mid-potency
describe the consequence of long-term topical steroid use
skin thinning; but sometimes we actually want that in otitis patients!
-issue is that tissue is hyperplastic, so if can treat tissue back to 50-70% thinner, can create a much larger lumen = recurrence less likely
describe the kirby-bauer disk diffusion test
- measures zones of inhibition of microbial growth around an antibiotic-impregnated dick
- the antibiotic concentration in the disk is standardized and usually based on average blood concentrations of antibiotics after a single oral dose
- MIC/minimal inhibitory antibiotic concentration:
-a series of antibiotic concentrations and incubated with a defined number of bacteria an the concentration of antibiotic where the microbes stop growing is the MIC
describe how topical antibiotics relate to antibiotic resistance and how to monitor therapy
topicals reach MUCH higher concentrations than the antibiotic concentrations used in KB tests or reported in MIC tests
so we NEVER do cultures in otitis externa because topicals we use are so much beefier than the resistance reported
instead we use repeat cytologies to monitor therapeutic progress
describe otitis media
- inflammation and/or infection of the middle ear (behind tympanic membrane, air-filled bone embedded space)
- in 16-82% of dogs with otitis externa
-risk increases with duration of otitis externa and severity and number of previous episodes of otitis externa
-less common in cats than in dogs - can be a consequence of:
-extension of otitis externa (most common pathway in dogs!)
-ascending infection from auditory tube (most common in humans/cats)
-auditory tube malfunction
-hematogenous spread
describe the symptoms of otitis media
- could be none!!
- fever, anorexia, depression
- inability to chew hard things, pain reaction when opening the mouth
- facial nerve paralysis
-ear droop, lip droop, upper eyelid droop/ptosis, nostril collapse, nostril dryness) - Horner’s syndrome_
-miosis, ptosis, sunken eyeball/enophthalmos, 3rd eyelid protrusion - KCS/dry eye
- conductive hearing deficiency/hearing loss
*symptoms occur on the SAME SIDE as the affected ear
*neuro signs due to anatomical proximity of middle ear to facial nerves (VII for facial muscles), sympathetic nerves (pupil constriction, eyelid elevation, 3rd eyelid prolapse, globe retraction)
describe otitis interna
- inflammation and/or infection of the inner ear
- over 50% of the inner ear is embedded in bone
-houses the cochlea: responsible for hearing
-housing the vestibular organ: responsible for balance
-these both have windows/holes in the bone that are covered only in a membrane structure (WEAK) - much less common than OE and OM!
- can be a consequence of:
-extension of otitis media (most common pathway in dogs and cats)
-hematogenous spread
-masses/growths
-foreign bodies
-trauma to head
describe symptoms of otitis interna
- hearing loss
- peripheral vestibular disease:
-head tilt, circling, falling towards affected side) - general incoordination
- nystagmus
- in worst case: can lead to meningitis and/or meningoencephalitis (death):
-lymphatic ducts connect inner ear to brain
*neuro signs due to impairment of vestibulocochlear nerve (CN VIII)
describe treatment of bacterial otitis media and interna
- longterm (>3 months) treatment with systemic antibiotics
-cocci: cephalexin, cefpedoxime, amoxi/clav, clindamycin
-rods: enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin - +/- myringotomy (make hole in ear drum):
-ideally, culture of drained material and bulla flushing if possible - +/- topical ear treatment after myringotomy
but we don’t know for sure we will treat!
are any regular ear cleaners safe for ears with potentially ruptured ear drums/OMI/diseased ears?
NO!
anyone can make an ear cleaner, just have to show that it’s safe for healthy ears
if anything, saline only!!
what medicated ear drops are safe for middle ears?
NONE
can cause deafness and neuro symptoms (esp with gentamicin-containing products)
-if you must, compounded ear drops:
–enrofloxacin+ dexamethasone SP “appears safe for middle ears”
describe indications for bulla osteotomy
- bulla osteomyelitis/osteolysis
- inspissated purulent material
- granulation tissue from chronic inflammation
- cats! due to anatomy
-cats have a bony septum in the bulla cavity so cannot access inner compartment with flushing and treating
