External and Middle Ear Pathology

Question 1

Define the external and middle ear

Answer 1

external = vertical and horizontal canals until the tympanic membrane
middle = cavity and ossicles up to the cochlea

Question 2

Define otitis and give the 3 types

Answer 2

otitis = inflammation of the ear.

externa (includes the pinna), media and interna

Question 3

Otitis externa (OE) clinical signs

Answer 3

reddening of pinna
swelling
thickening (possibly hyperkeratosis)
hot to the touch
ear scratching
pain
head shaking / head rubbing
hair loss
smell
discharge –> may be ceruminous (black waxy) or purulent
heat tilt if more sinister

Question 4

Aetiology of OE

Answer 4

PRIMARY (allergies, parasites (most common Notoedres cati, Otodectes cynotis), foreign bodies (commonly grass seeds and previous medications), pyoderma, keratinisation disorder, ear neoplasia, endocrine diseases)

SECONDARY (bacteria, yeasts)

PERPETUATING (ear canal stenosis, ulceration, otitis media, ear cartilage mineralisation)

PREDISPOSING (conformation, humidity, inappropriate cleaning, irritant treatments, systemic disease)

HYPERSENSITIVITIES (Type I (ectoparasites, ingested allergen reaction) and Type IV (allergic contact dermatitis) ending up in chronic otitis externa and dermatitis)

KERATINIZATION DISORDERS

GLANDULAR DISORDERS (ceruminous gland hyperplasia and ectasia, altered rate and altered type of secretion)

AUTOIMMUNE DISEASES (systemic diseases so the ears are involved)

VASCULAR DISEASES (frostbite, vasculitis, juvenile cellulitis and auricular chrondritis)

Question 5

Describe the diagnostic approach for OE

Answer 5

complete history
otoscopy
ear swabs taken for cytology, culture and sensitivity

other potential tests include haematology, biochemistry, endocrine testing, mineral levels and allergy panels

Question 6

Otitis Media (OM) clinical signs

Answer 6

reddening of pinna
swelling or thickening of pinna
hot to the touch
extreme pain
ear scratching
head shaking
head rubbing
hair loss
smell
discharge (ceruminous or purulent)
possible facial nerve paralysis (pupil constriction, eyelid drooping, eyeball sinking into the cavity, protrusion of third eyelid)
head tilt
coordination / balance issues
nystagmus

Question 7

How do you diagnose OM ?

Answer 7

sedation of anaesthesia to work deeper
similar steps to OE but consider additional imaging

Question 8

OE predisposing factors

Answer 8

ear conformation (breed dispositions, a narrow or stenotic external acoustic meatus, excessive hair)

excessive moisture (swimming, humid climate)

excessive cerumen production

treatments (trauma, topical irritation, dysbiosis, often owner caused)

obstructive ear disease (disorders of growth, inflammation, etc…)

systemic disease (immune suppression, debilitation, catabolic states, etc…)

Question 9

What are the main routes of ear infection ?

Answer 9

extension from the external environment

haematogenous spread (vessels depositing stuff)

extension up from the middle ear

Question 10

Define an aural (pinnal) haematoma

Answer 10

blood oedema in the pinna of the ear, intrachondrially or subparachondrially

caused by head shaking, self-trauma or secondary to OE

can lead to cartilage fractures

Question 11

Describe the gross appearance of OE

Answer 11

acute phase –> erythema, warmth, oedema, otorrhea (discharge), otorrhagia (bleeding from the ear) and otodynia/otalgia (ear pain)

chronic phase –> nodular proliferative lesions, thickening, bosselation (protrusions)

severe cases –> canal stenosis, chronic pinnal haematomas and insipissated ceruminous debris

Question 12

Describe the histological appearance of OE

Answer 12

hyperplasia (hallmark of inflammation)
dermal changes (such as oedema, fibrosis and mixed inflammation)
osseous metaplasia of soft tissues in the ear

net effect = narrowing of the external acoustic meatus (stenosis)

Question 13

Define myringitis

Answer 13

inflammation of the tympanic membrane

Question 14

What are the routes of pathogenesis for OM

Answer 14

perforation of the tympanic membrane
ascension along the auditory tube
extension via degeneration of the temporohyoid joint
extension via erosion of the tympanic bulla
migration along the vascular or neural pathways

Question 15

Gross appearance of OM

Answer 15

acute –> suppurative exudate (creamy and pale/tan), oedematous and thickened mucoperiosteum, +/- ulceration

chronic –> polypoid projections of mycoperiosteum, thickened, firm tissue (fibrosis), osteolysis of auditory ossicles and septations of bulla

Question 16

Define auricular hypoplasia

Answer 16

microtia (small pinna), normal in some breeds

Question 17

Define nasopharyngeal polyps

Answer 17

pedunculated to polypoid, pale tan mass with a smooth surface. histologically a fibrovascular core with lymphocytes, plasma cells and histiocytes

Question 18

Define tympanokeratomas

Answer 18

excessive keratin production (NOT A NEOPLASM).
grossly, tympanic cavity is filled with pasty, yellow-tan material that is keratin
histologically, underwhelming, keratin surrounded by squamous epithelium granulation tissue

Question 19

Name the common neoplasms of the ear

Answer 19

epithelial cell - adenoma, papilloma, carcinoma
melanocytes - melanomas
cartilage - chondroma, chondrosarcoma
bone - osteoma, osteosarcoma
leukocytes - lymphoma, mast cell, etc…
endothelium - haemangioma, haemangiosarcoma

MOST COMMON = ceruminous gland adenocarcinoma