Medical management and diagnostics that look for an underlying cause of otitis externa/media should always be performed prior to surgical intervention. Surgery only comes into play when conservative strategies are unlikely to benefit the patient. Scenarios that require surgical intervention include:

 Chronic recurrent or unrelenting otitis externa that has resulted in external ear canal stenosis

 Extension of otitis externa to otitis media

 The presence of benign (e.g., cholesteatoma) or malignant masses within the middle or external ear

It should be noted that all ear surgery results in significant pain. This is especially true for lateral approaches such as vertical or total ear canal resections. Therefore, appropriate analgesia is an absolute requirement before, during and after these procedures. The author prefers to place a fentanyl patch on the patient the day prior to surgery. In animals that will have surgery performed bilaterally, the patch should be placed over the thorax rather than the neck so that it does not interfere with the surgical site. The patch is covered with a bandage and precautions are taken to make sure that heating pads, which would result in potential overdose of fentanyl, are not placed over this area. Additional pre- and postoperative antiinflammatories (e.g., carprofen), α₂ agonists (e.g., medetomidine) and/or narcotics should be used in all cases. Local nerve blocks should also be considered.

Every owner should be carefully informed of any side effects associated with ear surgery. It is useful to have visual aids to help owners understand the following:

 The facial nerve exits the skull just caudal to the tympanic bulla and then runs cranially ventral to the horizontal canal. In severe cases of otitis or in dogs/cats with tumours that are escaping the external canal, this nerve may actually become 'wrapped-up' in the local disease process. Damage to the facial nerve results in loss of blink response, and facial paresis. Neuropraxia (swelling of the nerve) in our experience occurs in <10% of canine otitis cases and is usually transient, resolving in <1 month. Others have reported a higher occurrence rate (up to 46%). The affected eye must be medicated frequently until the blink response returns in order to prevent corneal ulceration. Transection of the nerve obviously results in facial paralysis--this is rare. We only worry about this when performing a total ear canal ablation-lateral bulla osteotomy (TECA-LBO).

 Sympathetic fibres running along the medial wall of the tympanic bulla on their way to the ciliary ganglia can become damaged/stretched whenever performing middle ear surgery. This will result in a usually transient Horner's syndrome in <10% of canine cases. In cats, transient Horner's is much more common following middle ear surgery (e.g., ventral bulla osteotomy: 83-96%) than in dogs. This is probably because the cat's middle ear is divided by a bony septum through which these fibres run, and which must be breached by the surgeon to ensure complete removal of middle ear tissues (usually polyps).

 The inner ear may be breached with excessive curettage of the dorsomedial tympanic bulla, which results in a damaged round window. This may result in vestibular signs postoperatively (head tilt, ataxia and nystagmus). Again, this is an uncommon complication and usually transient, but if you don't warn the owner about the possibility ahead of time, the chances for this occurring are guaranteed to increase.

 Hearing loss. Conflicting results have been reported in the literature. Most dogs with chronic otitis media have significant hearing loss prior to surgery, and continue to function similarly postoperatively.

 Haemorrhage. Any of the lateral approaches result in profuse haemorrhage from cut cartilage surfaces and deeper tissues. In addition, there are several vessels in the area of the bulla that must be avoided (e.g., retroglenoid vein). The author would not perform any lateral approach to the ear without cautery. These are often difficult and deep approaches: any loss of visibility greatly increases the chance of failure or iatrogenic damage.

Note: TECA-LBO and VBO (ventral bulla osteotomy) in dogs are very demanding procedures. The author did not feel comfortable doing these until after at least 12 of each. Referral should be strongly considered.

Total Ear Canal Ablation

Indications for TECA-LBO

 Chronic otitis: any dog/cat with complete obliteration of the horizontal canal, or with nearly complete occlusion and middle ear involvement. In addition to the potential complications noted above, recurrent otitis media with subsequent fistulation has been reported in 3-15% of cases. This is due in most cases to incomplete removal of epithelium within, or attached to, the bulla. The possibility of a necessary second surgery should be discussed with the owner prior to TECA-LBO. Although there are relatively few cases reported in the literature, a lateral approach to explore the fistula and reexamine the bulla appears to be the most successful with seven out of ten dogs experiencing resolution following a single exploratory surgery.

 Neoplasia: any dog/cat with neoplastic involvement of the external ear canal if the mass is confined to the canal. Biopsy and computed tomography (CT) scan should be performed first. When the tumour has escaped the confines of the canal, surgery's only role is to debulk the mass prior to radiation therapy. Animals with ceruminous adenocarcinomas of the external canal can have extended survival following surgery with clean margins, or adjunctive surgery followed by radiation therapy.

Subtotal Ear Canal Ablation

A modification of the TECA technique for dogs with erect ears has been described. The purpose of the modification was to avoid a change in ear carriage associated with excision of the medial portion of the auricular cartilage. An inverted L-shaped skin incision is made over the vertical canal, just ventral to the auricular cavity, to facilitate exposure. The annular cartilage of the vertical canal is transected at this point, followed by routine dissection and removal of the remaining vertical and horizontal canals. The horizontal portion of the L-shaped skin incision is sutured to the remaining cut-end of the vertical canal. The distal portion of the vertical canal is thus preserved resulting in a stoma just ventral to, and communicating with, the external orifice. This procedure was performed in three dogs with chronic otitis externa/media with no apparent problems reported at 1-year follow-up.

A more recent report evaluated the cosmetic outcome of a modified TECA technique in six cats. Erect ear carriage was maintained by creating a ventrally based advancement flap after circumferential incision around the external acoustic meatus and removal of the entire vertical and horizontal ear canal.

The following is a description of a subtotal ear canal ablation technique that the author has used for the treatment of otitis externa/media, or horizontal external ear canal masses in dogs and cats. It was initially performed as a method to maintain erect ear carriage, and then expanded to include a subset of dogs with pendulous ears. In each case, the medial surface of the pinna and the distal auricular cavity were free of, or minimally affected by, the underlying disease process.

A single vertical incision is made overlying the vertical ear canal from just ventral to the mid-point of the external orifice to ventral to the horizontal ear canal. With the aid of retractors, the central portion of the vertical ear canal is freed from its soft tissue attachments using blunt and sharp dissection and then transected. The proximal portion of the vertical canal and the horizontal canal are then removed as for a standard total ear canal ablation. Following lateral bulla osteotomy and curettage, the cut end of the distal vertical ear canal is grasped and elevated. The medial and lateral vertical ear canal cartilages are apposed with multiple simple interrupted or cruciate sutures using absorbable monofilament material. Care is taken to avoid penetrating the epithelium of the vertical canal with the sutures. Subcutaneous and skin closure is then performed in a routine manner. The result is a shallow blind-ended auricular cavity with preservation of the entire circumference of annular cartilage surrounding the external orifice.

We have performed this technique in 18 dogs and one cat. One dog and the one cat had benign masses present within the horizontal ear canal. Animals with otitis had minimal or no involvement of the distal ear canal. Postoperative dermatological problems associated with the remaining ear canal and pinnae were minor in four animals and protracted in four others. All complications resolved with medical management. Median time to follow-up was 12 months (mean: 21 months; range 3-53 months). Normal ear carriage is maintained in animals with erect ears, and this technique results in an ear that appears surgically unaltered. The technique is similar to a previously reported modification of a lateral ear canal resection.

Many owners of animals with erect ears are not concerned about ear droop following standard TECA, yet methods to prevent its occurrence should be discussed prior to surgery. Subtotal ear canal ablation preserves erect ear carriage and eliminates the dissection through and around the medial aspect of the auricular cartilage that is required for a standard TECA. The subjective impression of the surgeons performing this procedure is that it is easier to perform than a standard TECA, results in less haemorrhage and may be less painful. Prospective studies are needed to address these issues. Because of these potential benefits, as observed following performance of subtotal ear canal ablation on several dogs with erect ears, it was subsequently performed on nine dogs with pendulous ears and minimal or no distal ear canal involvement.

Animals that have masses or gross changes to the vertical ear canal secondary to otitis externa are not candidates for subtotal ear canal ablation. This would include most pendulous eared breeds, including Cocker Spaniels, which typically have significant involvement of the distal ear canal and auricular cavity by the time TECA is considered. The risk of recurrent disease in the remaining vertical canal would be too great to warrant these tissue-sparing techniques. Six of 24 ears (25%) developed protracted auricular cavity skin infections which eventually resolved with medical management. This compares to a similar presence of recurrent dermatological problems associated with the pinna in 10 of 38 (26%) dogs following the standard TECA technique. Although all superficial infections were corrected with medical management, owners should be made aware of that possibility prior to performing subtotal ear canal ablation, even if there is no distal involvement at the time of surgery, and standard TECA-LBO should be discussed as an alternative.

Five animals (26%) without neurological signs at presentation developed transient facial nerve paresis/paralysis. While retraction could have contributed to facial nerve trauma in these cases, the frequency of this complication is similar to previous evaluations of the standard TECA technique. The subjective impression of the surgeons who have performed this procedure is that facial nerve identification and retraction is no more difficult than with a standard TECA, although in the cat the skin incision was modified to improve exposure. As with the standard technique, owners should be made aware of the possibility of postoperative neurological complications.

References

1.  Beckman SL, Henry WB Jr, Cechner P. Total ear canal ablation combining bulla osteotomy and curettage in dogs with chronic otitis externa and media. Journal of the American Veterinary Medical Association 96: 84-90.

2.  Buback JL, Boothe HW, et al. Comparison of three methods for relief of pain after ear canal ablation in dogs. Veterinary Surgery 1996; 25: 380-385.

3.  Kyles AE. Transdermal fentanyl. Compendium of Continuing Education 1998; 20: 721-726.

4.  Mason LK, Harvey CE, Orsher RJ. Total ear canal ablation combined with lateral bulla osteotomy for end-stage otitis in dogs. Results in thirty dogs. Veterinary Surgery 1988; 17: 263-268.

5.  Matthiesen DT, Scavelli T. Total ear canal ablation and lateral bulla osteotomy in 38 dogs. Journal of the American Animal Hospital Association 1990; 26: 257-267.