Pinna and external ear canal

Question 1

According to Watt 2020 in Vet Surg, what was the most likely region of the bulla to have epithelial remnants following TECA-LBO?

Answer 1

Rostral (36% of cases).
Medial section had the least (2%).

Question 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?

Answer 2

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%).

Question 3

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?

Answer 3

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.

Question 4

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?

Answer 4

7% and 8% respectively.

Question 5

Foramina in the auricular cartilage of the ear allow passage of blood in which direction?

Answer 5

From the convex to the concave surface.

Question 6

What is the name of the cartilage that demarcates the lateral opening of the ear canal?

Answer 6

Tragus

Question 7

The caudal auricular artery is a branch of what artery?

Answer 7

The external carotid.

Question 8

What is the cartilage that connects the auricular cartilage of the horizontal ear canal to the external osseous meatus?

Answer 8

The annular cartilage.

Question 9

The external osseous meatus of the ear is an extension of what bone?

Answer 9

The temporal bone. It is 5-10 mm in dogs.

Question 10

The facial nerve exits the skull through what structure?

Answer 10

The stylomastoid foramen (caudodorsal to the osseous ear canal).

Question 11

Which nerves supply motor and sensory innervation to the external ear canal?

Answer 11

Motor: facial.
Sensory: vagus.

Question 12

What vascular structures are closely associated with the external ear canal?

Answer 12

1. Ventral: external carotid artery, maxillary vein.
2. Cranial: retroglenoid vein.
3. Medial: internal carotid artery.

Question 13

What is the cause of aural hematoma?

Answer 13

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.

Question 14

What happens without treatment of aural hematoma?

Answer 14

Fibrosis of the hematoma and ossification of the cartilage leading to disfigurement.

Question 15

What are premalignant changes of the skin associated with UV exposure called (typically progress to SSC)?

Answer 15

Actinic keratitis

Question 16

What is the treatment for actinic keratitis?

Answer 16

Pinnectomy or laser surgery. Prevention involves avoidance of the sun.

Question 17

How much more likely are white cats to develop SCC?

Answer 17

13 times.

Question 18

What is the treatment for SCC of the pinna?

Answer 18

1. Partial pinnectomy/total pinnectomy (1-2 cm margins).
2. Pinnectomy with vertical ear canal ablation.
3. 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.
4. Laser ablation.
5. Radiation therapy (strontium-90).
6. Chemotherapy.
7. Photodynamic therapy.

Question 19

What is the metastatic rate of SCC of the pinna?

Answer 19

Relatively low, but imaging of the chest and assessment of regional LNs still recommended.

Question 20

What was the MST for cats undergoing pinnectomy for SCC?

Answer 20

799 days.

Question 21

What is the difference between hemangioma and hemangiosarcoma of the pinna?

Answer 21

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.

Question 22

What is the treatment for basal cell carcinoma of the pinna?

Answer 22

Surgical excision. Usually curative.

Question 23

What is the difference between mast cell tumours of the pinna in cats and dogs?

Answer 23

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.

Question 24

Are histiocytomas of the pinna more common in male or female dogs?

Answer 24

Male (2.5:1)

Question 25

What is the treatment for sebaceous adenomas of the pinna?

Answer 25

Surgical or laser excision.

Question 26

What are the causes of otitis externa?

Answer 26

1. Primary causes: parasites (ear mite), foreign bodies, hypersensitivity (particularly food, atopy), keratinization disorders (underlying endocrinopathy), autoimmune disease. 2. 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. 3. Perpetuating factors: proliferation and overcolonization of bacteria (staph, pseudomonas, strep, proteus), and yeast (malassezia).

Question 27

What is the most common bacterial pathogen implicated in otitis externa in dogs?

Answer 27

Staph intermedius. Different bacterial populations between ears in the same patient is observed in 68% of dogs.

Question 28

In what percentage of dogs is a ruptured tympanic membrane diagnosed with concurrent otitis externa?

Answer 28

18%

Question 29

Are neoplasms of the external ear canal more frequently benign or malignant in dogs and cats?

Answer 29

Dogs: malignant (60%). Bilateral disease rare. Cats: malignant (88%). Bilateral disease common. Ceruminous adenocarcinoma is the most common malignancy in both species.

Question 30

What breed of dog might be predisposed to tumours of the external ear canal?

Answer 30

Cocker spaniels.

Question 31

Is ceruminous adenocarcinoma of the external ear canal locally aggressive in dogs and cats?

Answer 31

Yes, often invade the cartilage (50% dogs, 60% of cats). However, rarely cross the auricular or annular cartilage to invade the periaural tissues.

Question 32

What is the treatment for ceruminous gland adenocarcinoma?

Answer 32

TECA/BO. Radiation has also been used with varied success (for untreated or incompletely excised tumours)

Question 33

What is the MST for dogs following TECA/BO for ceruminous gland adenocarcinoma?

Answer 33

5.3 months if extensive involvement of the bulla and ear canal, 30 months if confined to the vertical or horizontal ear canal.

Question 34

What is the MST for cats following TECA/BO for ceruminous gland adenocarcinoma?

Answer 34

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.

Question 35

Where does traumatic avulsion of the ear canal most commonly occur?

Answer 35

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.

Question 36

What are clinical signs associated with traumatic avulsion of the external ear canal?

Answer 36

Facial swelling, otic discharge, head tilt, or periaural pain and irritation.

Question 37

What is the treatment for traumatic avulsion of the external ear canal?

Answer 37

1. Isolation of the horizontal ear canal segment, debridement, and suturing of the auricular cartilage to the skin. 2. TECA-LBO. 3. Horizontal ear canal ablation and LBO. 4. Primary repair of the annular/auricular separation (if acute).

Question 38

What are treatment options for congenital external auditory canal atresia?

Answer 38

1. Pull-through of the horizontal canal to the overlying skin. 2. TECA-LBO. 3. Nothing, if no clinical signs (although a blind ended atretic ear canal will accumulate ceruminous debris resulting in facial pain, swelling, and discomfort). 4. Drainage of the distended blocked canal.

Question 39

What is the most common cause of para-aural abscessation?

Answer 39

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.

Question 40

What diagnostics should be performed in the work-up of external ear disease?

Answer 40

1. Otoscopy. 2. Otic cytology and biopsy. 3. Radiography (including 20 degree lateral, and 30 degree rostral open mouth projections). 4. CT (+/- contrast). 5. MRI (most useful for differentiation between peripheral and central causes of vestibular disease). 6. 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).

Question 41

Does an intact tympanic membrane on otoscopy rule out otitis media?

Answer 41

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.

Question 42

In what percentage of cases do isolates from the bulla differ from isolates of the horizontal ear canal?

Answer 42

90%

Question 43

Are leukocytes found on cytology of the normal ear canal?

Answer 43

No. Their presence indicates exudative inflammation.

Question 44

What are the appearance of abscesses, neoplasia, and cholesteatomas on contrast CT of the external ear?

Answer 44

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.

Question 45

Following bulla osteotomy, what changes might be expected in the bulla on repeat CT?

Answer 45

Multiple possibilities: 1) obliteration with fibrous connective tissue, new bone, or granulation tissue. 2) partial or complete reformation.

Question 46

What surgical instruments in addition to a routine pack might be useful for surgery of the external ear?

Answer 46

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.

Question 47

What are treatment options for aural hematomas?

Answer 47

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.

Question 48

What are complications associated with treatment of aural hematoma?

Answer 48

Cosmetic alterations, recurrence, necrosis of the pinna.

Question 49

What suture pattern might be useful for repair of full thickness tears of the pinna?

Answer 49

Vertical mattress (deep throws can be used to realign the cartilage and superficial throws can be used to realign the skin).

Question 50

Following pinnectomy of cats for SCC, the skin on which surface of the ear should be pulled over the cut auricular surface?

Answer 50

The skin on the convex surface should be pulled over the cut edge and sutured to the skin on the concave surface.

Question 51

When is surgical treatment of otitis externa indicated?

Answer 51

When medical therapy has failed, the aural integument appears irreversibly diseased, there are cutaneous fistulae or para-aural abscessation, or otitis media/interna.

Question 52

What are indications for lateral wall resection of the ear?

Answer 52

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.

Question 53

What is the purpose of the draining board in lateral wall resection of the ear?

Answer 53

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.

Question 54

What is the biggest post-operative concern following lateral wall resection of the ear?

Answer 54

Self-trauma. Failure rates are also high (43-55%).

Question 55

What are indications of vertical ear canal ablation?

Answer 55

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.

Question 56

What are indications for TECA-LBO?

Answer 56

Ceruminous gland adenocarcinomas, extensive benign disease, failed lateral wall or vertical ear canal resection, and extension of disease into the middle ear cavity.

Question 57

What is the most common breed in which TECA-LBO is performed?

Answer 57

Cocker spaniels (43-60%).

Question 58

When performing TECA-LBO, dissection of the cartilage should ideally be performed deep to which layer?

Answer 58

The perichondrium.

Question 59

Where is the facial nerve located during TECA-LBO?

Answer 59

Caudoventral to the external ear canal at the level of the terminal horizontal canal.

Question 60

Why should stray dissection of the bulla be avoided during TECA-LBO?

Answer 60

To avoid damage to the retroglenoid vein rostrally, and the carotid artery and maxillary vein ventrally.

Question 61

Rongeurs are used to remove what structure to facilitate lateral bulla osteotomy?

Answer 61

The external osseous prominence ventrally.

Question 62

Aggressive curettage should be avoided in which part of the middle ear during LBO?

Answer 62

Dorsally, in the location of the round window. Care should also be taken to preserve the ossicles, if possible.

Question 63

Why might VBO rather than LBO be required in some brachycephalic dogs?

Answer 63

The bulla may be medial to the mandible. Pre-operative CT is useful to delineate which dogs might benefit from this approach.

Question 64

Why might subtotal ear canal ablation be performed? What are the risks with this technique?

Answer 64

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).

Question 65

How might pinna cosmesis be preserved in cats following TECA?

Answer 65

1. Folding and suturing of the caudal part of the base to the rostral part. 2. Use of a ventrally based, single-pedicle advancement flap.

Question 66

Is culture required at the time of TECA-LBO?

Answer 66

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).

Question 67

What is the cause of recurrent otitis media, fistula development, and para-aural abscessation following TECA-LBO?

Answer 67

Incomplete removal of annular cartilage, inadequate debridement and removal of middle ear epithelium, and presence of residual debris from the external or middle ear.

Question 68

What is the outcome following TECA-LBO for otitis externa?

Answer 68

Largely successful (improvement in 57-92% of patients).

Question 69

What are complications associated with ear canal surgery?

Answer 69

1. Nerve damage: Horner's syndrome and facial nerve paralysis. 2. Hemorrhage. 3. Dehiscence. 4. Postoperative deafness.

Question 70

Why does Horner's syndrome occur after ear canal surgery?

Answer 70

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.

Question 71

What are the clinical signs of Horner's syndrome?

Answer 71

Clinical signs include miosis, ptosis, enopthalmus, and prolapse of the third eyelid.

Question 72

Is the risk of Horner's syndrome higher in dogs or cats following ear surgery?

Answer 72

Cats (27-42% of cats have Horner's following TECA/BO, and it is permanent in 14-27%).

Question 73

What are clinical signs of facial nerve palsy?

Answer 73

Drooped ipsilateral lip, no ipsilateral blink reflex, dropped affected ear.

Question 74

What percentage of cats and dogs suffer facial nerve injury following TECA/BO?

Answer 74

Dogs: 13-39% (permanent in 4-13%). Cats: 12-56% (permanent in 28%).

Question 75

How is hemorrhage from the retroglenoid vein best managed during TECA?

Answer 75

Packing of retroglenoid foramen with bone wax (tends to retract making ligation impossible).

Question 76

How might dogs retain some hearing following bilateral TECA-LBO?

Answer 76

Acoustic bone conduction rather than air conduction.

Question 77

What is a cholesteatoma?

Answer 77

An epidermoid cyst of the middle ear, composed of keratin debris, epithelium and inflammatory cells.

Question 78

What are clinical signs associated with cholesteatoma?

Answer 78

Signs of otitis externa, with head tilt, facial palsy, pain on opening the mouth, and ataxia.

Question 79

What is the prognosis for cholesteatoma treated with TECA-LBO?

Answer 79

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.