Pinna and external ear Flashcards
What is the scutiform cartilage?
A cartilaginous structure sitting within the rostroauricular muscles medial to the ear. Was orignially part of the cranial helix spine, becoming detached at the time of birth
What is the annular cartilage?
Connects the horizontal canal to the osseous external auditory meatus. Attached to both the auricular cartilage and the temporal bone by fibrous connective tissue
What is cerumen?
Secretions of the deeper tubular ceruminous glands, more superficial sebaceous glands mixed with desquamated epithelium
What nerves supply sensory and motor function to the external ear canal?
- Sensory: CN X vagus
- Motor: CN VII facial
What important vessels surround the bulla?
- Rostral: retroglenoid vein
- Ventral: External carotid artery and maxillary vein
- Meidal: internal carotid artery
List DDx for neoplasia of the pinna
- Actinic keratosis (UVB - transform into SCC)
- SCC
- Haemangioma and HSA (UVB) - regrowth within 9.5m
- Basal cell tumours - Siamese, Himalayan, Persians predisposed (UVB). Surgical margin few mms
- MCT - Siamese overrepresented
- Histiocytoma - resolve spontaneously
- Sebaceous Adenoma - Sx or laser excison curative
- Sebaceous adenocarcinoma - more aggressive
- STS, FSA, rhabdomyoma, melanoma
List Tx options of pinna SCC
- Partial pinnectomy
- Complete pinnectomy
- Complete pinnectomy with vertical canal ablation
- Cryosurgery
- Laser ablation
- Radiation therapy
- Chemotherapy
How do pinna MCT differ in cats and dogs?
Cats:
- Typically benign, well circumscribed lesions
- Excision with narrow skin margin usually curative
Dogs:
- Regional LN mets in 42.8%
- 2cm margins sufficient unless tumour over 5cm
- Chemotherapy recommended for grade 3 or incompletely excised grade 2
- Radiation could be considered
List some inflammatory lesions of the pinna
Infectious
- Canine leproid granuloma syndrome (mycobacterium)
- Dermatophytosis
- Malassezia
- Feline cowpox virus
- Leishmania
- Sarcoptic mange
- Demodex
Inflammatory
- Allergic dermatitis
- Food allergy
- Atopic dermatitis
- Pemphigus
- Lupus (DLE/SLE)
- Vasculitis
List primary causes of otitis externa
- FB
- Parasites
- Hypersensitivity
- Keratinisation disorder
- Autoimmune disease
- Ear mites, demodex, sarcoptes
List some predisposing factors of otitis externa?
- Pendulous ears
- Narrow ear canals
- Excessive hair growth
- Excessive cerumen
- Chronic moisture
- Inappropriate antibacterial use
- Polyp or tumour
List some perpetuating factors of otitis externa
- Proliferation or overcolonisation of bacteria (Staph intermedius/pseudintermedius most common)
- Malassezia pachydermatitis
List DDx for neoplasia of the ear canal in dogs and cats
Dogs: 60% malignant
- Ceruminous carcinoma
- SCC
- Anaplastic carcinoma
- STS, melanoma, plasmacytoma
- Cocker Sp overrepresented
Cats: 87.5% malignant
- Ceruminous gland adenocarcinoma
- SCC
- Anaplastic carcinoma
- sebaceous adenocarcinoma
- Often have bilateral external canal carcinomas!
Benign:
- Papillomas, ceruminous adenoma, ceruminous cystadenoma, sebaceous adenoma, basal cell carcinoma, histiocytoma
- Often pedunculated
Where does ceruminous gland ACA arise from?
Modified apocrine sweat glands.
Locally invasive
What is the most common site of ear canal avulsion?
What are the treatment options?
Junction of auricular and annular cartilages
Tx options:
- TECA-LBO
- Horizontal canal ablation and LBO with preservation of vertical canal
- Primary repair through caudal approach
What is congenital external auditory canal atresia?
How can it present?
Result of improper development of ectodermal cells of the first branchial and pharyngeal clefts.
- Ear canal is functionally closed at birth and is patent again by 10 days. Failure of this process leads to atresia
Presentations:
- Haired skin covering external auditory meatus
- Blind termination of vertical canal half way down
- Atresia at junction between annular and auricular cartilages
In what % of cases is a paraural abscess reported after TECA-LBO?
6-11%
What is assoc with ulcerations of the external ear canal?
Gram negative organism such as pseudomonas
What CT changes may be seen with a cholesteatoma?
- Minimal contrast enhancement of tympanic bulla contents
- Ring enhancement in 25%
- Severe bone changes: osteolysis, osteoproliferation, osteosclerosis
Where does the facial nerve lie in relation to the ear canal?
Caudoventral to the terminal horizonal ear canal
List Tx options of aural haemotoma
- Repeated drainage
- Passive/active drains
- S-shaped incision with mutiple mattress sutures paralled to vessels
- CO2 laser drainage and ablation
- Drainage with instillation of dex and concirrent oral dex - successful 92.9%
- Drainage and methylpred - successful 90-98%
What is used to close a pinnectomy?
Simple continuous, nonabsorbable sutures
List the surgical options for lesions of the external ear canal
- Lateral wall resection
- Vertical canal ablation
- TECA-LBO
Where should aggressive curettage of the bulla be avoided?
Dorsally - round window
