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Canine ear canal surgery considerations
How to choose between lateral wall resection and total ear canal ablation.
Ear canal surgery in dogs can be performed for diagnostic or therapeutic purposes, or a combination of these. As a therapeutic procedure, surgery can be considered either for definitive treatment or as an adjunct to ongoing medical treatment.
It's important to select the appropriate type of surgery to avoid either insufficient treatment (and the possible need for revision surgery later) or overtreatment, which could expose the patient to a greater number of (or more severe) complications.
Lateral ear canal resection
Lateral ear canal resection is primarily indicated in cases of refractory otitis externa in which glandular or epithelial hyperplasia and stenosis are not contributing factors. The operation entails making parallel incisions in the cranial and caudal aspects of the lateral portion of the vertical ear canal and then leaving the ventral border of the resultant flap intact (in some cases, the cartilage of the flap is also scored). The extent of ventral incisions and dissection is determined by the point at which the vertical canal transitions to the horizontal canal.
The surgical goal is to have a flap that lays flat (hence the preference of some surgeons to score the ventral margin) at or slightly below the level of the horizontal canal's base. This provides direct access to, allows aeration of and permits gravity-dependent drainage from the horizontal canal.
The cartilage flap is sutured to adjacent skin to provide a drain board, while the skin is sutured over the cartilage's cut edges of the remaining vertical canal. When making the parallel incisions in the cartilage, don't allow the incisions to converge (as is the natural tendency), lest the base of the flap end up narrower and more fragile than the drain board.
The improved aeration and drainage lateral ear canal ablation provides may be curative or at least allow an easier and more successful continuation of medical treatment. However, in dogs with established hyperplasia or stenosis or in breeds in which this is common (e.g., cocker spaniels), lateral ear canal resection usually fails, so it should not be used. In some cases, the procedure can be used to visualize and excise nonmalignant masses on the medial aspect of the vertical canal that aren't accessible from the normal opening.
Total ear canal ablation
Total ear canal ablation (TECA) entails the removal of the entire external ear canal from the medial aspect of the pinna to the osseous tympanic bulla. Because diseases that may necessitate the use of TECA also commonly involve the tympanum and middle ear cavity, bulla osteotomy (BO) is almost always performed in conjunction with TECA (TECA-BO).
Indications for TECA-BO include end-stage otitis externa, especially those cases with hyperplasia and stenosis, and malignant neoplasia within the ear canal. In the latter instance, wider resection in the mastoid region may be required for complete tumor removal with effective margins (usually based on preoperative cross-sectional advanced imaging with computed tomography or magnetic resonance imaging).
Most candidates for TECA-BO are dogs with often painful, malodorous otitis that has become refractory to all other treatments—both topical and systemic. Many affected dogs also have mineralization of their ear canals that virtually precludes any other effective treatment besides ablation. Cultures of microorganisms obtained before surgery may or may not show the actual flora present deep within the canal or middle ear cavity. Hence, it's usually valuable to obtain such cultures from the tympanic bulla and external auditory meatus at the end of TECA-BO surgery, since this may provide a more accurate representation of pathogenic bacteria. Consider both aerobic and anaerobic cultures.
Note that many dogs with end-stage otitis are affected bilaterally, and it's common to perform bilateral surgery concurrently.
Hazards during lateral ear canal resection include injury to the parotid salivary gland and the facial nerve's superficial branches. Long-term complications can include stricture or stenosis of the newly created opening to the horizontal canal and progression of the underlying otitis despite the surgery and ongoing medical therapy, necessitating revision surgery (usually conversion to TECA).
Potential complications with TECA-BO are more numerous and serious. These include facial neuropraxia or neurotmesis with resultant transient or permanent paralysis, severe hemorrhage from branches of the maxillary artery, vestibular dysfunction if trauma to the inner ear occurs during bulla osteotomy or curettage and late abscess formation if a nidus of infected tissue is left in situ. The latter potential complication provides a rationale for the aforementioned cultures during surgery, as those results may help guide antibiotic therapy should a late infection or abscess occur.
Although a surgeon's experience and meticulous dissection help avoid most of these complications, many dogs undergoing TECA may have such severe mineralization and distortion of their ear canals, or periauricular inflammation and fibrosis, that iatrogenic neurovascular trauma is unavoidable. Because some dogs with end-stage otitis have an underlying atopic dermatitis, these patients may yet have some pinna dermatitis problems that require ongoing treatment even after successful TECA.
Markedly decreased hearing acuity is expected after bilateral TECA in dogs with no other abnormalities. Patients with bilateral end-stage otitis undergoing TECA usually already have marked hearing loss before surgery, and the differences between preoperative and postoperative acuity is typically less dramatic or problematic. Nonetheless, be sure to discuss deafness with the clients as part of the preoperative consultation.
Despite the potential complications after TECA-BO surgery, most dogs have a vastly improved quality of life compared with their preoperative status. The clients also may report improved companionship with their pets, as they no longer have to chase their dogs to apply painful treatments. The alleviation of chronic pain also allows many of these dogs to regain a more tractable personality.
Other ear canal surgeries, such as vertical ear canal resection, may also be considered based on the indications, with the goal again being to do enough surgery to achieve the desired long-term objective, without the need to do more extensive surgery that might increase the risk for complications.
Dr. Fingeroth is senior staff surgeon at the Orchard Park Veterinary Medical Center in New York. He is also a consultant to the Veterinary Information Network in the areas of orthopedics and general soft tissue surgery, as well as oncologic, endocrine and neurosurgery. He has been ACVS board-certified since 1988.