Ear diseases are common in dogs and cats and surgical options are often required. Surgical procedures for ear disease fall into three main categories; surgery of the pinna, surgery of the ear canal and osteotomy of the tympanic bulla.

Surgery of the Pinna

Resection of the Pinna

This is most often required for treatment of squamous cell carcinoma (SCC) in cats. Hair is clipped from the pinna and the margins of the SCC determined. The resection should ideally include 1 cm of normal tissue around the lesion. The external ear canal is cleaned and cotton wool inserted to reduce contamination of the surgical field.

A pair of curved, atraumatic forceps, like a Satinsky clamp, is applied across the ear base. This provides haemostasis and also a template for removal of the pinna to ensure symmetry if both ears are to be removed. The pinna is removed sharply along the line of the clamp. Enough skin of the caudal pinna is mobilised to allow it to be folded over the cut end of the pinna and sutured to the skin inside the pinna. The cut edge of the pinna is sutured using a continuous pattern of an absorbable suture material, such as Vicryl Rapide^TM. Bleeding is usually transient once the clamp is removed. The resected pinna is turned over and may be used as a template to guide resection of the other side. A broad-spectrum antibiotic is administered perioperatively but there is little indication to continue antibiotics postoperatively. The cat is discharged with analgesic medications and the suture should fall out or be rubbed out within 3 weeks of surgery. If suture remains after that time, or creates irritation, it can be removed manually in a tractable patient.

Drainage of Aural Haematomas

This is a common procedure and most veterinary surgeons have adopted a strategy that provides the maximum chance of success with minimal complications. A variety of methods of treating aural haematomas have been reported, including injection of corticosteroids to treat a suspected underlying immune-mediated condition, and insertion of cannulae through stab incisions to provide drainage. In general, the haematoma is drained by making an incision through the thin skin on the inner surface of the ear. The pinna cartilage consists of two layers (internal and external) and the haematoma usually dissects between these two layers, necessitating incision of the inner layer as well as the skin. The incision is lengthened enough to provide adequate drainage of the entire haematoma cavity; some authors recommend multiple incisions and others use an S-shaped incision to reduce the risk of pinna distortion after granulation and contraction of the resulting wound. A series of mattress sutures are used to obliterate the haematoma cavity by healing of skin to cartilage and of the two cartilage layers. In some cases, veterinary surgeons will use a splint of X-ray film or some other product to add rigidity and exert pressure on the ear as it heals. Some veterinarians choose to bandage the ear and others do not. The advantage of bandaging the ear is that the dog cannot traumatise it by shaking its head, and there is less spraying of blood. A disadvantage is the need for hygiene and the risk of wound infection and otitis externa due to the moist conditions.

Surgery of the Ear Canal

Surgery of the ear canal is usually performed in animals with chronic otitis externa, or those with aural neoplasia. Ceruminous adenomas in dogs, while often spectacular in their presentation, commonly arise from a 'stalk' attached to the mucosa of the vertical or horizontal ear canal and can be treated effectively by resection of the appropriate section of ear canal. Ear canal stenosis as a result of traction trauma is another reported indication for ear canal resection.

Lateral Ear Resection

This is performed in animals likely to benefit from increased aeration of the ear canal, or to facilitate delivery of medication. Lateral ear resection is also useful in patients that may require regular otoscopy, such as cats with inflammatory polyps. Lateral ear resection facilitates removal of inflammatory polyps that may otherwise be difficult to grasp, and allows for easy visualisation of the ear canal subsequently to check for recurrence.

The success of lateral ear resection is contingent upon creating a new stoma with the horizontal ear canal that is widely patent and allows the horizontal canal to drain effectively. Incisions are made in the cranial and caudal wall of the vertical ear canal and continued down until the membranous connection between the scrolls of vertical and horizontal ear cartilage is encountered. Once this membrane is reached, it is possible to fold the vertical ear cartilage flap ventrally without kinking of the stoma. The cartilage flap is sutured to surrounding skin under enough tension to pull the stoma ventrally. Careful apposition of the mucosa to the skin is necessary to avoid development of a 360 degree cuff of granulation tissue that is likely to contract and cause a stricture. Fine absorbable sutures (1.5-2 metric (4/0 or 5/0 USP) Vicryl^TM) are used to avoid the necessity for anaesthesia or further trauma at suture removal.

Some morbidity is to be expected with lateral ear resection as the surgical site is often itchy and painful and superficial infection and otitis externa is common. Elizabethan collars and local anti-inflammatory medications help to reduce the degree of self-trauma. Lateral ear resection is rarely a definitive treatment for chronic otitis externa, which usually has an immune-mediated basis, and clients should be advised that the main objective of surgery is to make management easier.

Vertical Ear Canal Ablation

This is used in cases with stenosis of the canal due to chronic inflammation or trauma, or in patients requiring resection of neoplasia. The same principles apply as for lateral ear canal ablation, with extreme care in anastomosis of the horizontal canal to the skin required to ensure a patent stoma postoperatively.

Total Ear Canal Ablation

This is reserved for patients with chronic end-stage otitis externa or neoplasia of the horizontal ear canal. The main complications of total ear canal ablation are profound deafness, facial nerve palsy or paralysis and postoperative abscessation. Facial nerve damage is common as the nerve is situated immediately rostral and ventral to the vertical ear canal and must be retracted during the surgical procedure. In some patients, aural inflammation or infection extends outside the ear canal causing nerve damage; therefore facial nerve function must be assessed in patients prior to surgery as well as immediately afterwards. Facial nerve palsy leads to facial drooping and attenuation of the palpebral reflex, necessitating application of artificial tears. It is usually reversible and animals rarely suffer major consequences as they remain able to protect their cornea by retracting the globe into the orbit and using the nictitating membrane. Postoperative abscessation usually results from failure to remove all the secretory epithelium from the bony part of the ear canal or middle ear and the likelihood of this can be reduced with careful attention to the dorsolateral aspect of the boney canal and the tympanic bulla.

Facial nerve palsy or paralysis can be avoided by dissecting as close as possible to the ear cartilage right down to bone. Dissection is undertaken 360 degrees around the annular cartilage so that it proceeds to an equivalent depth all the way around, ensuring the best visibility. Atraumatic retractors are used and assistants instructed not to exert too much pressure on retractors ventral and cranial to the canal. Once the canal has been dissected down to bone circumferentially, a no. 11 scalpel blade is inserted through the dorsal aspect of the cartilage into the ear canal and rotated 360 degrees to separate the cartilaginous from the bony canal. A curette is used to remove any remaining mucosa.

Lateral Bulla Osteotomy

Most surgeons combine total ear canal ablation with lateral bulla osteotomy by using a rongeur to cut a slot out of the tympanic bulla ventral to the opening of the osseous canal. This allows inspection of the tympanic bulla, curettage of mucosa and other soft tissue, and placement of a Penrose or closed-suction drain. The drain is left in situ for 48 hours, after which drainage is usually minimal. Microbiological swabs are taken from the tympanic bulla for culture and sensitivity and postoperative antibiotics administered accordingly. The bacterial population of the middle ear may not be predicted by results from culture of the external ear canal.