Ear disease 1 Flashcards
How common is otitis in general and referral derm practice?
General
Dogs - 4.7% probably under-reported
Cats - 2.1%
Referral
Dogs - 50-70%
Cats - 10-30%
What are the different types of ear disease?
Pinnal disease
Diseases affecting the ear flap
Otitis externa
Inflammation of the outer ear
Otitis media
Inflammation of the middle ear
Otitis interna
Inflammation of the inner ear
See neurology
What do most pinnal disease in general practice reflect?
otitis externa
What pruritic and non-pruritic pinnal diseases affect the different parts of the pinna?
What is the correct definition of otitis externa?
OE = inflammatory disease of the external canal
* Inflammation
* Accompanied by 2˚ infection and canal changes
How is cerumen formed?
Lipids + sloughed keratinocytes
What organisms are part of the normal flora in the ear canal? What factors can cause microbial overgrowth (or dysbiosis)?
Organisms
- Gram +ve cocci predominate (but no growth in some dog’s ears)
* Similar species to those found on the skin
* Micrococcus spp.
* Coagulase negative staphylococci, Staphylococcus schleiferi and Staphylococcus pseudintermedius
* Streptococcus species
* Malassezia and many others
Factors causing overgrowth
* Humidity
* Inflammation (and swelling)
* Reduced epithelial migration
* Epithelial surface changes
Most commonly:
* Staphylococcus pseudintermedius
* Malassezia pachydermatis
What does PSPPP stand for when managing otitis externa?
- Primary disease e.g. atopic dermatitis, Otodectes cyanotis
- Secondary disease e.g. Malassezia, Staphylococci & Pseudomonas spp.
- Predisposing factors e.g. Hairy &/or pendulous ears, stenosis
- Perpetuating factors e.g. Ear canal hyperplasia, stenosis and scarring
- Pain - Very common, difficult to manage in face of steroids
What are predisposing factors to otitis externa?
Conformation
* Excessive hair growth in canals (e.g. poodle)
* Hairy concave pinna (e.g. cocker spaniel)
* Pendulous pinna (e.g. basset hound)
* Stenotic canals (e.g. shar pei)
Excessive moisture
* Environment (heat & high humidity)
* Water (swimmer’s ear, grooming, cleaners)
Obstructive ear disease
* Feline apocrine cystadenomatosis
* Neoplasia & polyps
Primary otitis media
* Primary secretory otitis in CKCS, tumour or sepsis
Treatment effects
* Altered normal microflora (e.g. inappropriate cleaner)
* Trauma from cleaning or plucking
What are common primary causes of otitis externa?
- Parasites
- Otodectes cynotis
- Demodex spp.
- Scabies
- Foreign bodies
- Grass awns
- Hypersensitivity
- Atopic dermatitis, food hypersensitivity, medications
- Keratinisation disorders
- Primary idiopathic seborrhoea
- Hypothyroidism
- Glandular disorders
- Cocker spaniels, English springer spaniels & Labrador retrievers have increased ceruminous glands
- Miscellaneous
- e.g. feline proliferative & necrotising otitis externa
How should you treat octodectes cyanotis?
- Most ear creams are effective with localised disease
- Selamectin or moxidectin spot-on
- Likely that the isoxazoline group are effective
- May need a cleaner ± steroids
What are the most common foreign bodies causing otitis externa?
Grass seeds
What are secondary causes of otitis externa?
Bacteria
* acute disease
* Gram-positive bacteria
* Staphylococcus species
* Streptococcus species
* Corynebacterium species
* chronic disease
* Gram-positive bacteria
* Enterococcus species
* Gram-negative bacteria
* Pseudomonas species
* Proteus species
* Escherichia coli
Fungi
* Acute & chronic disease
* Malassezia spp.(common)
* Malassezia pachydermatis
* Lipid dependent Malassezia spp.
* Candida spp. (uncommon)
* Aspergillus spp. (v. v. uncommon)
What are perpetuating factors of otitis externa?
Pathological changes in the external ear canal
- Changes in canal wall
- Inflammation causing failure of epithelial migration
- Acute change: oedema, hyperplasia
- Chronic change: proliferative change, canal stenosis, calcification of pericartilaginous fibrous tissue
- Changes in glandular tissue
- Hyperplasia of ceruminous and sebaceous glands, hidradenitis
- Changes in the tympanum
- Dilation, rupture, diverticulum (false middle ear – cholesteatoma)
- Otitis media
- Acute
- foreign material
- mucopurulent exudate
- Chronic
- biofilm formation
- granulation material
- bony change in the bulla
- Acute
What are the clinical signs of OE?
Presenting reasons
* Aural / otic pruritus or headshaking
* Mild to marked exudate
* Malodour
* Head tilt
* Neurological or pain
* Deafness
* Often conduction
* May be toxic / neurological
Physical findings
- Erythema, swelling, scaling, discharge (otorrhea), malodour and pain
- Secondary
- pinnal lesions are common
- pyotraumatic dermatitis
- haematoma
What is the typical disease progression of OE?
- Secondary disease follows the primary cause
- Many / most cases are not presented until secondary disease is present
- Malassezia
- Staphylococci
- Gram negative rods
- If treated inadequately potential for anti-microbial resistance
- In many cases Pseudomonas aeruginosa is end point
- Malassezia
Progressive pathological changes occur with time
* Epidermal hyperkeratosis and hyperplasia
* Dermal oedema
* Fibrosis
* Ceruminal gland hyperplasia and dilation
* Abnormal epithelial cell migration
* Tympanic membrane alterations
* Otitis media (16% of acute OE, 50–80 % of chronic OE)
What clinical signs are associated with otitis media?
- Often non-specific – pain?
- Most often signs of concurrent OE are the most obvious clinical signs
- Deafness
- Pain on eating
- Signs of OI if progression
Horners: – sympathetic nerves to the face
* Drooping of the eyelid on the affected side (ptosis)
* The pupil of the affected eye will be constricted (miosis), or smaller than usual
* The affected eye often appears sunken (enophthalmos)
* The third eyelid of the affected eye may appear red and raised or protruded (conjunctival hyperemia)
Facial paralysis – CN VII
* Adult age Cocker Spaniels, Pembroke Welsh corgis, boxers, and English setters are most likely to experience this condition.
What are the consequences on otitis media?
- Conductive deafness
- Loss of drum
- High pressure fluid/mucous in the middle ear
- Chronic OE or OM ± cholesteatoma
- Horner’s syndrome / facial paralysis
- Ear and lip droop, asymmetrical lips, dribbling
- Keratoconjunctivitis sicca, neurogenic dry nose
- Anisocoria with ipsilateral miosis, ptosis of the upper eyelid etc.
- Vestibular syndrome (otitis interna [OI])
How can you diagnose OM?
- Appearance of the drum on video otoscopy
- Sampling of the middle ear for
- Bacteriology
- Fungal culture
- Cytology via myringotomy or ruptured TM
- Palpation of granulation tissue in the middle ear
- BAER (hearing testing)
- Imaging
How would you treat OM?
If intact drum
* Perform myringotomy and flush until clean
* Using cytology and culture data
* Use aqueous antibiotics (usually home prepared) 2-3 times a day following cleaning with saline or an appropriate aqueous cleaner (TRIZEDTA with 0.15 w/w chlorhexidine in dogs)
* Pain relief
* ? Role of systemic antibiotics
In severe cases
* Poor response to therapy
* Intractable OE
* Evidence of marked new bone on CT / radiographs
- Consider total ear canal ablation and bulla osteotomy or bulla osteotomy
- Seek advice from experienced or referral vets
What is primary secretory otitis media?
- Presented for deafness or neck pain!
- Marked mucoid build-up in the middle ear
- Bulging middle ear noted on otoscopy
- Repeated flushing and myringotomy (3-5 times)
- Sputolysin (mucolytic) and oral N-acetyl cysteine has been used by some
- Steroids are used to reduce mucous production
What are the indications for performing a myringotomy?
- Bulging TM with pain or neurological signs (Horner’s, vestibular signs, facial paresis)
- Tympanosclerosis (an “exploratory myringotomy”)
- Radiographic/MRI bulla changes and intact TM
- Evidence of tissue or fluid behind the TM
- Medically unresponsive vestibular disease with an intact TM
- Chronic otitis cases longer than 6 months that have not responded to treatment for otitis externa (requires judgement)
What are the steps of a myringotomy?
- Clean and dry the external ear canal
- Incision may be made using a 5-French polypropylene catheter (cut end to make sharper) or an open-ended tomcat catheter or a small wire (clitoral) swab
- Passed through either hand held or video otoscope
- Position: caudoventral aspect of the pars tensa to avoid damaging the tympanic germinal epithelium and the structures of the middle ear.
- Sampling: Pass swab(s) for cytology and bacteriology - instilling and then withdrawing a small amount of sterile saline solution
- Flush with saline (± other agents depending on the cytology results)
What is BAER? How is it performed?
Brainstem auditory evoked response
* Click applied to tested ear (white noise to other)
* Peaks of response respond to transition through differing structures (e.g. peak I = vestibulocochlear nerve)
* Normal dog – threshold <10dB
Why is radiography insensitive for OM?
- Insensitive way of assessing OM: see thickening of wall of the bulla in chronic disease
- Lateral, lateral oblique and open mouth views.
- Changes absent in many cases of OM
What causes otitis interna? What clinical signs are associated? What are differential diagnoses?
Cause
* extension of OM (majority)
* haematogenous and ascending infection via the auditory tube
* adverse drug reaction
Clinical signs
* Head tilt to the affected side
* Spontaneous or rotatory nystagmus
* Asymmetric limb ataxia with preservation of strength
* Falling
* Vomiting and/or anorexia
Differential diagnoses
* Other peripheral vestibular diseases
* Idiopathic vestibular syndrome
* Neoplasia (vestibulocochlear nerve)
* Hypothyroidism
Seek advice from experienced or referral vets
How would you diagnose and treat OI?
- Establish the presence of systemic disease and/or localised disease (OE/OM)
- Pruritus, headshaking and pain around the TMJ may be useful indicators of local disease
- Complete neurological examination
- Otic examination ± myringotomy
- MRI (possibly CT)
In the absence of another cause, long term use of systemic antibiotics has been advocated.
* Ability to cross the BBB
* Based on culture of the middle ear?
What are ototoxic neurological signs? What should you do?
Profound hearing loss and vestibular signs may be seen
- Seek specialist advice / consider referral
- Remove the product from the ear as soon as possible
- Repeat cytology and bacteriology
- Anaesthesia and flush the area gently with saline
- Give high anti-inflammatory dose of dexamethasone systemically
- Consider the use of appropriate antibiotics (choose a drug that crosses BBB)
- Withdraw topical therapy temporarily
- Report to the manufacturer / Veterinary Medicines Directorate
