Total Ear Canal Ablation and Subtotal Bulla Osteotomy

Introduction

Otitis externa is an insidious disease that is not usually debilitating, and the associated clinical signs are generally controlled until medical therapy is withdrawn. When multiple attempts at medical treatment fail, ear disease invariably progresses, and more extensive surgery is indicated to permanently relieve the clinical signs. Owners must understand that the frequency and severity of intra- and postoperative complications increase in proportion to the degree of surgery required. Thus, for the most part, early surgical intervention should be strongly advised when appropriate medical treatment for otitis externa fails or the condition becomes recurrent. As the ear tissue damage becomes irreversible from chronic infection, drainage procedures fail and removal of the entire horizontal and vertical ear canal is required. This salvage procedure is known as total ear canal ablation (TECA). Secondary middle ear infection frequently develops in dogs with end-stage otitis externa. Consequently, variable results and high complication rates have been reported when TECA is performed without a means of middle ear exposure and debridement (bulla osteotomy and curettage). Because TECA eliminates a primary pathway for exudate drainage, the external canal, recurrent deep infection occurs unless the middle ear is adequately evacuated. Inadequate removal of the secretory epithelium within the bulla or short osseous ear canal is responsible for such longstanding complications as persistent fistulation and abscessation. For these reasons, most surgeons routinely combine lateral bulla osteotomy (LBO) through the same approach used for TECA. These combined procedures are described in this chapter.

Indications

TECA is most often performed for irreversible inflammatory ear canal disease in dogs. Other less common indications include severe ear canal trauma, invasive neoplasia, and certain congenital malformations obstructing horizontal ear canal drainage. Irreversible inflammatory ear canal disease is present when one or a combination of the following is observed: hyperplasia of the epithelium occluding the horizontal ear canal, collapse or stenosis of the horizontal ear canal caused by infection within the cartilage or bone, or severely calcified periauricular tissue observed on skull radiographs.
Many dogs that present to the veterinarian for surgical treatment of inflammatory ear disease do not readily fall under the previous list of irreversible conditions or indications for TECA. If medically unmanageable otitis externa is related to an ongoing generalized skin condition such as atopy or hypothyroidism, treatment of the primary dermatologic disorder often helps control the ear problem. Intercurrent skin disorders are very common in dogs with otitis externa. Almost 80% of dogs undergoing TECA in one report had one or more primary dermatologic diseases including seborrhea, pyoderma, hypothyroidism, and atopy. When the related primary skin condition has been thoroughly diagnosed and appropriately treated but continues to be unresponsive, I prefer TECA for treatment of persistent otitis externa in these patients instead of surgical drainage procedures. As the skin disorder progresses, so will the ear disease in most circumstances, and a lateral ear resection or vertical ear canal ablation will subsequently fail due to progressive inflammatory changes in the remaining canal. Similarly, if owners are incapable or unwilling to treat the skin or chronic ear disease appropriately, TECA may be indicated before irreversible changes exist.
Although TECA combined with LBO is indicated for a number of conditions in the dog, it is uncommonly performed on cats. Irreversible, proliferative inflammatory changes resulting from long standing otitis externa does not appear to form as readily in cats as it is does in dogs. Cats with otic tumors, such as ceruminous adenocarcinoma or basal cell carcinoma, diffuse polypoid disease, or those sustaining severe trauma to the ear canal are potential candidates for TECA. TECA is not usually required for cats affected with otitis media or inflammatory middle ear polyps, since the external ear canal is usually not severely affected, and exposure to the source of the clinical problem is best achieved with the ventral approach (ventral bulla osteotomy). [...]