Winkie LynchAcc 140663Trisha Oura, DVM10/25/2010

11 yo MC Shih Tzu Presents for evaluation of large soft palate

mass 6 mos progressive respiratory stridor and

increased effort, decreasing activity, recent onset dysphagia

Palate mass seen on exam by rDVM

Winkie Lynch

Sedated oral exam: large mass deviating the soft palate ventrally, obstructing view of the epiglottis

FNA of mass: kertainized squamous debris◦ Inconclusive interpretation due to low cellularity

CT:

Winkie Lynch

Primary Differential:Cholesteatoma

Severe otitis media Usually not expansile

Neoplasia◦ Middle/inner ear

Usually soft tissue swelling w/ contrast enhancement Usually permeative lysis of tympanic bulla/petrous

temporal bone◦ External ear

Soft tissue mass within ear canal (enhancement)

DDX

Epidermoid cyst within the middle ear

Keratin debris surrounded by keratinized stratified squamous epithelium

VRUS paper describes 3 components (cyst, matrix, perimatrix) but not really used

What is a Cholesteatoma?

Congenital◦ Start with a normal, intact tympanic membrane◦ No otitis media◦ Inclusion or rest of squamous epithelium forms a cyst◦ Can be recognized late in life

Acquired1. Metaplastic transformation of normal epithelium2. Retraction of tympanic membrane into middle ear3. Migration of epithelium from perforated membrane into middle ear4. Basement membrane breach w/ migration of cells from membrane into subepithelial space

Most cases in dogs occur w/ otitis media (therefore = acquired)

How are Cholesteatomas Formed?

Slow or rapid expansion of cyst◦ Keratin or sebaceous material accumulates

Mild-severe inflammatory response◦ Cytokine production varies◦ Can become infected

How are Cholesteatomas Formed?

Cholesterol granuloma reported in few dogs◦ Benign expansive lesions that develop in middle

ear and other normally aerated bony cavities◦ Occurs w/ hemorrhage, obstruction of ventilation◦ Cholesterol precipitates (from RBC membrane or

mucosa) to form crystals granulomatous reaction

24% of people w/ cholesteatoma have cholesterol granulomas◦ Also occur w/ chronic otitis media, tumors

Role of Cholesterol?

Incidence > 11% of dogs with otitis media

Several case series:◦ M > F, mean age ~ 7 yo◦ Many with history of chronic otitis

Clinical signs (similar between reports): ◦ Head tilt◦ Peripheral vestibular◦ Ataxia◦ Pain on opening mouth◦ Increased respiratory noise/respiratory effort (rare)

Signalment/Signs

CT features of middle ear cholesteatoma in dogs. VRUS. 2010. 51(4):374-379◦ Unilateral expansile mass w/o contrast

enhancement** Keratin debris = avascular = no enhancement

◦ Severe bone changes (slow progressive growth) Lysis, proliferation, sclerosis

◦ Minimal air remains in the tympanic bulla◦ Rarely, periosteal reaction associated with adjacent

TMJ

**prev. reports with heterogeneous enhancement

CT Findings

CT Findings

Trigeminal canal enlargement Pre-contrast cholesteatoma Post-contrast cholesteatoma

Imaging FindingsCT MRI

Cholesteatoma Non-contrast enhancingExpansileHyper-attenuating to brain

T2 hyperintenseLow/intermediate T1 signal

Cholesterol granuloma

Non-contrast enhancingNon-expansileIso-attenuating to brain

T2 hyperintenseT1 hyperintense

** if cholesteatoma and cholesterol granuloma coexist, appearance can be heterogeneous and difficult to interpret

Surgical removal◦ Removal all keratin debris and epithelium

Recurrence◦ Risk factors: inability to open mouth, neurologic signs, bone

lysis, P.aeruginosa◦ Recurrence in humans ~ 5-50%

If no TECA-BO, need chronic treatment with open external ear canal to allow removal of debris

Winkie had TECA-LBO & VBO◦ Cultured S.pseudointermedius, E. faecalis

Treatment/Prognosis

Hardie EM, KE Linder, AP Pease. Aural cholesteatoma in twenty dogs. Vet Surg 2008;37:763-770.

Little CJ, et al. Inflammatory middle ear disease of the dog: clinial and pathological features of cholesteatoma, a complication of otitis media. Vet Rec 1991;128:319-322.

Travetti O, et al. Computed tomography features of middle ear cholesteatoma in dogs. Vet Radiol US 2010;51:374-379.

References