Several surgical techniques are described to assist in the management of otitis external and media; however, total ear canal ablation and ventral bulla osteotomy are the two procedures that are typically indicated. In rare circumstances a lateral wall resection will be appropriate. Total ear canal ablation is always combined with a lateral bulla osteotomy and is a salvage procedure to manage otitis external/media and rare circumstances neoplasia of the external ear canal. Ventral bulla osteotomy is indicated for assisting in the management of otitis media which does not have concurrent otitis external and nasopharyngeal polyps arising from the middle ear. In rare circumstances lateral wall resection has an indication for facilitating the management of otitis external; however, case selection needs to be stringent. The specifics of the indications for each procedure are as follows:
Total Ear Canal Ablation
1. Chronic end stage ear disease - defined by:
a. Calcification of external ear canal.
b. Corticosteroid therapy does not reduce the ear canal stenosis.
c. Permanent loss of tympanic membrane with repeated accumulation of debris with in middle ear.
2. Otitis externa/media that has failed to respond to intensive medical management that the owner/dog will tolerate.
3. Changes to the ear canal (such as stenosis) which make it impossible to provide topical medication.
4. Failure following previous surgery (lateral wall resection or vertical canal ablation) .
5. Neoplasia of the external ear canal.
6. Ear canal trauma though primary repair can be performed in acute presentations.
Ventral Bulla Osteotomy
1. Isolated otitis media.
2. Inflammatory nasopharyngeal polyps in cats.
Ventral bulla osteotomy facilitates an approach to both bullae if there is bilateral disease present.
Lateral Wall Resection
1. Performed before irreversible hyperplastic changes have occurred.
2. To improve the morphology of the ear canal.
a. Extremely hairy ears (e.g., Bichon Frise).
3. As an adjunct to medical treatment in dogs with minimal changes to the ear canal but a propensity to otitis. It is vital that owners understand that they are likely to need to continue medical treatment and that the surgery is designed to facilitate this and reduce the need for a total ear canal ablation and lateral bulla osteotomy (TECA/LBO).
4. In very rare cases, to manage ear canal neoplasia if it is affecting the lateral side of the vertical canal.
Total ear canal ablation, ventral bulla osteotomy and lateral wall resection have the potential for significant complications. Understanding the potential complications helps reduce the likelihood of these occurring.
Complications of TECA/LBO
Loss of hearing cannot really be described as a complication as it is an anticipated outcome. However, it is important to warn owners and make sure they understand that their dog may be less responsive when not in a direct line of sight. If owners are concerned about hearing loss it is advisable to assess hearing prior to surgery as the diseased ear is likely to have minimal hearing anyway.
Haemorrhage - if either of the vessels in the region of the external meatus are traumatised then haemorrhage can be severe and difficult to stop. It can be hard to visualise the bleeding point and ligation is almost impossible. If brisk bleeding is encountered then pack the area with swabs and apply firm pressure for ten minutes (by the clock), and then remove the swab and re-examine. Surgical ligating clips can be useful in this area although the facial nerve is vulnerable. In severe cases closing the incision over a swab with planned re-operation to remove the swab and complete the surgery may be necessary.
Some breeds of dog have anatomy which makes the surgery more challenging. In brachycephalic breeds (Bulldogs particularly) the zygomatic process and retroarticular process are very prominent and make the final part of the dissection of the ear canal extremely awkward.
Immediate Post-Operative Complications
Facial nerve paresis/paralysis - even with good surgical technique facial nerve function can be absent after surgery. It seems to be of relatively little consequence though the eye on the affected side must be monitored and if necessary apply hypromellose drops to lubricate. Typically it is secondary to neuropraxia rather than transection and function usually returns within 4–6 weeks.
Vestibular signs - Occasionally dogs can suffer from profound vestibular signs. This complication seems to be more common if there is excessive curettage in the bulla in the region of the vestibular (oval) window. The signs usually abate within 2–3 days. Anti-emetic therapy and nutritional support might be necessary.
Late Post-Operative Complications
Discharging sinus - These usually appear just caudal to the pinna and can take years to become apparent. Typically due to failure to remove all of the epithelium in the region of the external osseous meatus. Re-operation is required usually via a ventral bulla osteotomy.
Complications of Ventral Bulla Osteotomy
Potential complications associated with ventral bulla osteotomy include hypoglossal nerve paresis, Horner's syndrome, vestibular disease and inadequate drainage with continued otitis externa.
Complications of Lateral Wall Resection
Dehiscence post-surgery is not uncommon (~ 27% of cases). The most common complication of ear canal resection is ongoing otitis externa and progression of the secondary changes in the ear canal. Only 30–50% of dogs benefit from this procedure and the poor results are usually due to performing the surgery too late. Pre-existing pathology that results in failure of the procedure, other causes of failure include making the "washboard" too narrow with constriction at its base, failure of the procedure to adequately drain the horizontal canal, failure to recognize and treat any underlying disease (hypothyroidism, primary idiopathic seborrhoea) and middle ear disease.
Performing a TECA/LBO - Critical Steps
Essential instrumentation includes suction, diathermy, Gelpi retractors x 2, excellent surgical lighting.
Make a circumferential incision around the ear canal with a scalpel. Started dissection on the medial side where the tissues are looser. Keep dissection as close as possible to the ear canal, transect muscles close to the cartilage of the ear canal to minimise haemorrhage.
Use an Allis tissue forceps or towel clip to grasp the ear canal to allow the ear canal to be moved into the desired position. Apply tension to the tissues to identify where the canal is still attached.
Keep dissection close to the ear canal, generally the facial nerve is not seen.
Transection of the canal is the most hazardous part of the procedure due to the facial nerve caudoventrally to the canal, and the superficial temporal artery (a primary branch of external carotid a.) and the retroarticular (sometimes called retroglenoid) vein.
Once the canal has been removed use a Freer elevator to elevated soft tissue off the bulla surface laterally to facilitate exposure of the lateral aspect of the bulla. The bulla osteotomy is performed using rongeurs to remove a window of bone from the bulla to enlarge the external meatus. The shape of the osteotomy with the meatus should resemble a keyhole.
Copiously flush and suction the bulla. Curettage is cautious avoiding the dorso-medial aspect of the epi-tympanic recess (location of the oval window). Meticulously curettage the bony external meatus to removal all remnant epithelium from this region.
Generally a horizontal linear closure produces as good a cosmetic for the pinna. For erect ears a simple advancement flap can be created advancing skin from ventral to dorsal into the surgical wound to improve the ear carriage.
Performing a Ventral Bulla Osteotomy - Critical Steps
A paramedial skin incision is made just medial to the mandibular salivary gland centered midway between angular process of mandible and the wings of the atlas and centered over the external auditory meatus. Deep palpation (especial in cats) will locate the bulla prior to creating the incision.
The platysma muscle is incised and frequently thicker than anticipated. Blunt dissection between the digastric muscle (medial to it) and stylo/hyoglossal muscles is performed.
The hypoglossal nerve is located on the lateral aspect of the hypoglossus muscle and followed down to the bulla.
The bulla is identified in the angle between the hypoglossal nerve/lingual artery and the maxillary artery.
A Steinmann pin just extending beyond the jaws of a hand chuck is used to penetrate the bulla and the stoma enlarged with rongeurs.
A bone curette is used to remove the epithelial lining of the bulla, care with the dorsal aspect.
The tympanic bulla of cats is divided into ventro-medial and dorso-lateral compartments and both compartments need to be opened.
Performing a Lateral Wall Resection - Critical Steps
Parallel skin incisions are made at the rostral and caudal margins of the opening of the external acoustic meatus which are 1.5x the length of vertical canal to extend to at least 1 cm ventral to floor of the ear canal.
Rostral and caudal full thickness cuts are made in the cartilage using scissors, starting from intertragic (lateral) and pretragic fissures (medial), distally to the annular cartilage. Care is taken to avoid narrowing of the cartilage flap and hence stenosis of the opening created.
The cartilage flap is trimmed to 1/3–1/2 of its length and folded distally to form a "washboard".
The cartilage is sutured to the skin using a nonabsorbable monofilament suture with the edges apposed under minimum tension.