SURGERY OF THE EAR
Chronic infections that thicken and occlude the ear canal and tumors that fill the middle ear or external ear canal are the most common problems requiring surgery on the ear. In fact, the conformation of the ear canal predisposes it to infection, especially in certain breeds of dogs such as Cocker Spaniels, Golden Retrievers and Poodles. Large, floppy ears, hair-filled ear canals, and the moist warm environment all contribute to infection that smolders and becomes very difficult to control or eliminate.
Since the ear cannot be kept dry, and because an infection thickens the tissues of the ear canal, proliferative debris is trapped in the ear. This prevents topical ear medications from contacting the infectious agents. The end result is a vicious cycle of worsening infection and severe permanent changes in the ear.
The ear is divided into three distinct regions (Fig.1). The EXTERNAL EAR is the ear canal. It is "L" shaped and ends at the tympanic membrane (ear drum). This shape predisposes the ear to infection in the dog because it creates a bottleneck for debris, ear wax, and moisture to accumulate and irritate the delicate canal wall. The MIDDLE EAR is within a hollow, bony portion of the skull, known as the bulla. The INNER EAR is located next to the bulla and is responsible for equilibrium and balance. Any of these areas may be affected in a disease process. They are best evaluated by direct otoscopic examination and, frequently, radiographic (x-ray) evaluation.
Three basic types of surgery can be performed depending upon the regions of the ear that are affected.
LATERAL EAR RESECTION
Early in the disease process it may be possible to perform a Lateral Ear Resection (Fig.2). This procedure is used for diseases of the external ear and involves removing and reconstructing a small lateral portion of the ear canal. This facilitates drainage of the ear canal and permits application of medications directly into the ear canal.
Occasionally, only the middle ear is affected. This occurs when an ear canal infection causes the ear drum to rupture, allowing infection into the middle ear. The ear drum then "regrows" as the ear canal infection is treated. This is especially common in cats that have polyps. In these cases the bony wall of the bulla is opened surgically either from the side or from under the neck to gain access to the middle ear. Drains are placed to evacuate the infection. This procedure is known as a BULLA OSTEOTOMY (Fig.3).
TOTAL EAR CANAL ABLATION AND BULLA OSTEOTOMY
More severe infections require a more involved surgery called a Total Ear Canal Ablation and Bulla Osteotomy (Fig.4). Preoperative radiographs of the skull are generally recommended to assess changes that have taken place in the bony portion of the ear. The infected tissue and entire ear canal are removed. The bony portion of the ear (bulla) is opened to remove all of the infectious tissue from around the hearing apparatus. Bacterial cultures are obtained so that the infection may be treated with the appropriate antibiotics. On occasion, biopsies may be indicated to identify abnormal tissue in the ear. Drains are placed to encourage healthy tissue growth without abscess pocket formation.
The surgery is usually successful in alleviating the painful, debilitating chronic ear infections, as they cannot recur once the ear canal has been removed. Fortunately, hearing loss, which is directly related to the severity of the infection within the middle ear, is not always associated with this surgery. Dogs frequently retain some degree of hearing capacity, even without ear canals, and are much more comfortable.
1998, Southern California Veterinary Surgical Group