Pinna and external ear canal Flashcards
According to Watt 2020 in Vet Surg, what was the most likely region of the bulla to have epithelial remnants following TECA-LBO?
Rostral (36% of cases).
Medial section had the least (2%).
According to Banks 2023 in Vet Surg, what 3 neurologic signs were brachycephalic dogs more likely to exhibit compared to other breeds when presenting for TECA-LBO? Were imaging findings typically more or less severe in brachycephalic patients? Were post-operative outcomes different?
Facial nerve paralysis, Horner’s, vestibular signs. Also more likely to present acutely.
Imaging signs more severe in brachycephalic dogs, including bilateral changes, aural masses, para-aural abscesses, otitis interna, and brainstem changes.
No difference in complications between groups (overall complication rate of 28%).
In a study by Folk 2022 in JAVMA, administration of culture based antimicrobials within 1-month post-operative reduced the risk of infection related complications in TECA-LBO by how much? Patients not administered antimicrobials were how many times more likely to require revision surgery? What was the most common bacterial growth?
Patient receiving antimicrobials within 1-month post-operative were 86% less likely to develop infection related complications.
Patients not administered antimicrobials were 10 times more likely to require revision surgery.
Staphylococcus was the most common bacteria isolated.
In a study by Pieper 2023 in JVIM, what were the recurrence rates for ceruminous gland adenomas and adenocarcinomas of the external ear canal treated by CO2 laser ablation?
7% and 8% respectively.
Foramina in the auricular cartilage of the ear allow passage of blood in which direction?
From the convex to the concave surface.
What is the name of the cartilage that demarcates the lateral opening of the ear canal?
Tragus
The caudal auricular artery is a branch of what artery?
The external carotid.
What is the cartilage that connects the auricular cartilage of the horizontal ear canal to the external osseous meatus?
The annular cartilage.
The external osseous meatus of the ear is an extension of what bone?
The temporal bone. It is 5-10 mm in dogs.
The facial nerve exits the skull through what structure?
The stylomastoid foramen (caudodorsal to the osseous ear canal).
Which nerves supply motor and sensory innervation to the external ear canal?
Motor: facial.
Sensory: vagus.
What vascular structures are closely associated with the external ear canal?
- Ventral: external carotid artery, maxillary vein.
- Cranial: retroglenoid vein.
- Medial: internal carotid artery.
What is the cause of aural hematoma?
Typically secondary to violent head shaking or scratching secondary to otitis externa.
Causes shearing of the blood vessels passing from the convex to concave side of the ear. Resultant dead space fills with blood.
What happens without treatment of aural hematoma?
Fibrosis of the hematoma and ossification of the cartilage leading to disfigurement.
What are premalignant changes of the skin associated with UV exposure called (typically progress to SSC)?
Actinic keratitis
What is the treatment for actinic keratitis?
Pinnectomy or laser surgery. Prevention involves avoidance of the sun.
How much more likely are white cats to develop SCC?
13 times.
What is the treatment for SCC of the pinna?
- Partial pinnectomy/total pinnectomy (1-2 cm margins).
- Pinnectomy with vertical ear canal ablation.
- Cryosurgery (-50 to -60 degrees, 2 freeze thaw cycles, with larger lesions the tumour can be resected and the base frozen). Complete resolution of lesions <5mm in one study.
- Laser ablation.
- Radiation therapy (strontium-90).
- Chemotherapy.
- Photodynamic therapy.
What is the metastatic rate of SCC of the pinna?
Relatively low, but imaging of the chest and assessment of regional LNs still recommended.
What was the MST for cats undergoing pinnectomy for SCC?
799 days.
What is the difference between hemangioma and hemangiosarcoma of the pinna?
Both UVB induced, but hemangiosarcoma is much faster growing, poorly circumscribed and is more likely to metastasize (lungs most likely).
MST for hemangiosarcoma is 9.5 months.
What is the treatment for basal cell carcinoma of the pinna?
Surgical excision. Usually curative.
What is the difference between mast cell tumours of the pinna in cats and dogs?
Cats: normally benign behaviour. Excision with narrow margins typically curative.
Dogs: prognosis dependent on grade (I, II, III, high/low). Regional LN metastasis reported in 43% of cases of aural mast cell tumours. Wide excision needed for cure. Chemotherapy may be prudent in high grade tumours or those expressing c-kit.
Are histiocytomas of the pinna more common in male or female dogs?
Male (2.5:1)
What is the treatment for sebaceous adenomas of the pinna?
Surgical or laser excision.
What are the causes of otitis externa?
- Primary causes: parasites (ear mite), foreign bodies, hypersensitivity (particularly food, atopy), keratinization disorders (underlying endocrinopathy), autoimmune disease.
- Predisposing factors: increase the risk for otitis but are not responsible in their own right, include; anatomic considerations (narrow ears, pendulous ears, hairy ears), chronic ear moisture, inappropriate antimicrobial use, presence of a polyp or a tumour.
- Perpetuating factors: proliferation and overcolonization of bacteria (staph, pseudomonas, strep, proteus), and yeast (malassezia).
What is the most common bacterial pathogen implicated in otitis externa in dogs?
Staph intermedius.
Different bacterial populations between ears in the same patient is observed in 68% of dogs.
In what percentage of dogs is a ruptured tympanic membrane diagnosed with concurrent otitis externa?
18%
Are neoplasms of the external ear canal more frequently benign or malignant in dogs and cats?
Dogs: malignant (60%). Bilateral disease rare.
Cats: malignant (88%). Bilateral disease common.
Ceruminous adenocarcinoma is the most common malignancy in both species.
What breed of dog might be predisposed to tumours of the external ear canal?
Cocker spaniels.
Is ceruminous adenocarcinoma of the external ear canal locally aggressive in dogs and cats?
Yes, often invade the cartilage (50% dogs, 60% of cats). However, rarely cross the auricular or annular cartilage to invade the periaural tissues.
What is the treatment for ceruminous gland adenocarcinoma?
TECA/BO.
Radiation has also been used with varied success (for untreated or incompletely excised tumours)
What is the MST for dogs following TECA/BO for ceruminous gland adenocarcinoma?
5.3 months if extensive involvement of the bulla and ear canal, 30 months if confined to the vertical or horizontal ear canal.
What is the MST for cats following TECA/BO for ceruminous gland adenocarcinoma?
49-50 months.
Neurologic signs at the time of diagnosis are poor prognostic indicators, as are histologic diagnosis of SCC or anaplastic carcinoma rather than ceruminous gland adenocarcinoma.
Where does traumatic avulsion of the ear canal most commonly occur?
At the junction of the auricular and annular cartilage.
If left untreated can result in formation of a pseudotympanic membrane and development of external auditory canal atresia. This results in obstruction of the external ear canal, and accumulation of ceruminous exudate.
What are clinical signs associated with traumatic avulsion of the external ear canal?
Facial swelling, otic discharge, head tilt, or periaural pain and irritation.
What is the treatment for traumatic avulsion of the external ear canal?
- Isolation of the horizontal ear canal segment, debridement, and suturing of the auricular cartilage to the skin.
- TECA-LBO.
- Horizontal ear canal ablation and LBO.
- Primary repair of the annular/auricular separation (if acute).
What are treatment options for congenital external auditory canal atresia?
- Pull-through of the horizontal canal to the overlying skin.
- TECA-LBO.
- Nothing, if no clinical signs (although a blind ended atretic ear canal will accumulate ceruminous debris resulting in facial pain, swelling, and discomfort).
- Drainage of the distended blocked canal.
What is the most common cause of para-aural abscessation?
Incomplete debridement of the epithelial lining of the tympanic bulla during previous TECA (6-11% of dogs).
Trauma, neoplasia, cat bites, foreign bodies, and erosive otitis externa are other potential causes.
What diagnostics should be performed in the work-up of external ear disease?
- Otoscopy.
- Otic cytology and biopsy.
- Radiography (including 20 degree lateral, and 30 degree rostral open mouth projections).
- CT (+/- contrast).
- MRI (most useful for differentiation between peripheral and central causes of vestibular disease).
- Contrast canalography and fistulography (rarely indicated clinically. Fistulography may be used to investigate fistulous tracts after TECA-LBO, but the technique is time-consuming and has frequent false-negative results).
Does an intact tympanic membrane on otoscopy rule out otitis media?
No, 71% of ears with proven otitis media have an intact tympanic membrane.
If there is any suspicion of otitis media a myringotomy should be performed.
In what percentage of cases do isolates from the bulla differ from isolates of the horizontal ear canal?
90%
Are leukocytes found on cytology of the normal ear canal?
No. Their presence indicates exudative inflammation.
What are the appearance of abscesses, neoplasia, and cholesteatomas on contrast CT of the external ear?
Abscess: central hypoattenuating region with ring enhancement.
Neoplasia: no ring enhancement, may have lysis of the contour of the tympanic bulla or temporal bone.
Cholesteatoma: little contrast enhancement, ring enhancement in 25% of cases with severe bone changes within the bulla.
Following bulla osteotomy, what changes might be expected in the bulla on repeat CT?
Multiple possibilities:
1) obliteration with fibrous connective tissue, new bone, or granulation tissue.
2) partial or complete reformation.
What surgical instruments in addition to a routine pack might be useful for surgery of the external ear?
Self-retaining retractors (typically Gelpis or Weitlaners, although a Lone Star retractor is favored by some), rongeurs for removing the terminal ear cartilage and dismantling the lateral bulla wall, and a variety of small curettes for middle ear debridement.
What are treatment options for aural hematomas?
1) Nonsurgical: drainage and injection with dexamethasone or methylprednisolone +/- oral steroids. May result in aural abscess if sterile technique is not used.
2) Surgical.
a. Passive or active drainage, teat cannulae. Best for acute cases with minimal fibrin.
b. Incisional drainage (S-shaped).
c. CO2 laser drainage.
d. Human fibrin sealant.
Bandaging of the ear should be performed following aural hematoma drainage.
What are complications associated with treatment of aural hematoma?
Cosmetic alterations, recurrence, necrosis of the pinna.
What suture pattern might be useful for repair of full thickness tears of the pinna?
Vertical mattress (deep throws can be used to realign the cartilage and superficial throws can be used to realign the skin).
Following pinnectomy of cats for SCC, the skin on which surface of the ear should be pulled over the cut auricular surface?
The skin on the convex surface should be pulled over the cut edge and sutured to the skin on the concave surface.
When is surgical treatment of otitis externa indicated?
When medical therapy has failed, the aural integument appears irreversibly diseased, there are cutaneous fistulae or para-aural abscessation, or otitis media/interna.
What are indications for lateral wall resection of the ear?
Congenital canal stenosis, small tumors of the tragus or lateral wall of the dorsal portion of the vertical canal, or otitis externa treatment when integumentary changes are considered reversible and surgery will improve the canal environment or facilitate medical management.
What is the purpose of the draining board in lateral wall resection of the ear?
Decreases the amount of sutures near the stoma, reduces the risk of stricture, and shifts hair bearing skin away from the stoma ventrally to aid in maintenance.
What is the biggest post-operative concern following lateral wall resection of the ear?
Self-trauma. Failure rates are also high (43-55%).
What are indications of vertical ear canal ablation?
Irreversible hyperplastic otitis, severe trauma, and neoplasia limited to the vertical canal.
It is rare for disease to be confined to the vertical ear canal, and so this procedure is rarely performed.
What are indications for TECA-LBO?
Ceruminous gland adenocarcinomas, extensive benign disease, failed lateral wall or vertical ear canal resection, and extension of disease into the middle ear cavity.
What is the most common breed in which TECA-LBO is performed?
Cocker spaniels (43-60%).
When performing TECA-LBO, dissection of the cartilage should ideally be performed deep to which layer?
The perichondrium.
Where is the facial nerve located during TECA-LBO?
Caudoventral to the external ear canal at the level of the terminal horizontal canal.
Why should stray dissection of the bulla be avoided during TECA-LBO?
To avoid damage to the retroglenoid vein rostrally, and the carotid artery and maxillary vein ventrally.
Rongeurs are used to remove what structure to facilitate lateral bulla osteotomy?
The external osseous prominence ventrally.
Aggressive curettage should be avoided in which part of the middle ear during LBO?
Dorsally, in the location of the round window.
Care should also be taken to preserve the ossicles, if possible.
Why might VBO rather than LBO be required in some brachycephalic dogs?
The bulla may be medial to the mandible. Pre-operative CT is useful to delineate which dogs might benefit from this approach.
Why might subtotal ear canal ablation be performed? What are the risks with this technique?
This involves maintenance of the dorsal vertical ear canal and medial cartilage of the pinna to maintain erect ear carriage. Main indication is for masses or anatomic abnormalities of the horizontal ear canal.
The main risk with this approach is that if the superficial vertical ear canal and medial pinna are not disease free, recurrent dermatologic problems can result (46% in one study).
How might pinna cosmesis be preserved in cats following TECA?
- Folding and suturing of the caudal part of the base to the rostral part.
- Use of a ventrally based, single-pedicle advancement flap.
Is culture required at the time of TECA-LBO?
Probably not if adequate resection of diseased tissues, debridement and lavage is performed (no difference in outcome between patients that did and did not receive perioperatve antimicrobials).
Exceptions may be immunocompromised patients or post-operative re-exploration of a tympanic bulla, or if there is evidence of osteomyelitis (bone culture would be appropriate in this instance).
What is the cause of recurrent otitis media, fistula development, and para-aural abscessation following TECA-LBO?
Incomplete removal of annular cartilage, inadequate debridement and removal of middle ear epithelium, and presence of residual debris from the external or middle ear.
What is the outcome following TECA-LBO for otitis externa?
Largely successful (improvement in 57-92% of patients).
What are complications associated with ear canal surgery?
- Nerve damage: Horner’s syndrome and facial nerve paralysis.
- Hemorrhage.
- Dehiscence.
- Postoperative deafness.
Why does Horner’s syndrome occur after ear canal surgery?
Damage to the postganglionic sympathetic fibers running through the middle ear (enter via the tympano-occipital fissure).
Generally secondary to overzealous debridement of the bulla.
What are the clinical signs of Horner’s syndrome?
Clinical signs include miosis, ptosis, enopthalmus, and prolapse of the third eyelid.
Is the risk of Horner’s syndrome higher in dogs or cats following ear surgery?
Cats (27-42% of cats have Horner’s following TECA/BO, and it is permanent in 14-27%).
What are clinical signs of facial nerve palsy?
Drooped ipsilateral lip, no ipsilateral blink reflex, dropped affected ear.
What percentage of cats and dogs suffer facial nerve injury following TECA/BO?
Dogs: 13-39% (permanent in 4-13%).
Cats: 12-56% (permanent in 28%).
How is hemorrhage from the retroglenoid vein best managed during TECA?
Packing of retroglenoid foramen with bone wax (tends to retract making ligation impossible).
How might dogs retain some hearing following bilateral TECA-LBO?
Acoustic bone conduction rather than air conduction.
What is a cholesteatoma?
An epidermoid cyst of the middle ear, composed of keratin debris, epithelium and inflammatory cells.
What are clinical signs associated with cholesteatoma?
Signs of otitis externa, with head tilt, facial palsy, pain on opening the mouth, and ataxia.
What is the prognosis for cholesteatoma treated with TECA-LBO?
Guarded, recurrence is common.
Likely secondary to incomplete removal or secondary cholesteatoma formation due to transfer of epithelium into the middle ear at the time of surgery.
