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SURGERY FOR OTITIS EXTERNA/MEDIA
Overview of the Condition
Otitis externa is an inflammation of the ear canal. Because dogs’ ear canals are L-shaped (Figure 1), fluid does not drain easily from canal openings. Additionally, the lining of the ear can become inflamed and thickened, blocking air and fluid flow in and out of the canal. Animals with otitis externa can also develop otitis media- middle ear inflammation. Similar to the problem seen in children (especially after airplane flights), fluid can build up behind the ear drum, causing pressure and pain. Otitis externa and media are common conditions in the dog, particularly in specific breeds such as the Cocker spaniel and German shepherd.
Figure 1. The ear canal (gray arrow) is vertical, or upright, near its outer opening, and then lies horizontal, or flat, as it nears the ear drum. The middle ear (black arrow) is separated from the ear canal by the ear drum or “tympanic membrane). This bony sac, or bulla, contains the openings to the inner ear where the hearing and balance organs are located.
Signs/Clinical Presentation
Dogs with otitis externa may start out with mild signs, such as scratching their ears or shaking their heads. The lining inside the pinna, or ear flap may become reddened, and then the skin may become thick and scaly. As the condition progresses, the ear canal produces discolored secretions. Dark brown thick waxy material may build-up around the canal opening, and the ears will have a strong unpleasant smell. Eventually the ear canal lining becomes so thick and reactive that it will take on a cauliflower-like appearance, and even block the opening (Figure 2). Dogs that have bacterial infections may also develop a white thick discharge from the ears. Because the condition is painful, particularly when the middle ear is affected, animals may have personality and behavioral changes. They may shy away from being petted on the head, and may be uncomfortable opening their mouth wide or chewing food. Additionally, blockage of the ear canal muffles their hearing and makes them less responsive to their owners.
Figure 2: Appearance of a Cocker spaniel with severe otitis externa of both ears. Note the severe cauliflower-like thickening at the area of the ear canal.
Risk Factors
In puppies and kittens, otitis externa is often caused by ear mites. These tiny parasites cause terrible itching and a thick brown discharge In adult dogs, the most common underlying cause is allergies- sensitivity to something in the environment or to food. In older animals, tumors can cause blockage of the ear canal and secondary infection. Other predisposing causes may include foreign bodies (such as grass seeds), or small ear canals (often seen in Shar peis) or long floppy ear flaps (for example, Basset hounds) that prevent air flow (Figure 3). Hormonal problems, such as poor thyroid function, or other underlying skin disorders may also be present. Bacterial and yeast infections are never the primary problem; while these cause the clinical signs in animals, it is important to determine what allowed the bacteria and yeast to grow in the ear canals in the first place.
Figure 3: This basset hound was born with narrowed ear canals that prevented drainage and air flow through the ear canals.
Diagnostic Tests
Unless a tumor, foreign body, or ear canal narrowing or blockage is present, otitis externa is usually treated medically. First, however, the veterinarian must determine the underlying cause of ear disease. The veterinarian will perform an otoscopic exam, looking down into the ear canal with a lighted scope, to see if there is anything unusual in the canal and will take samples from the ear to determine whether the dog has problems with yeast, bacteria, or mites. In some cases the ear canals are cultured to determine which antibiotics would be most helpful for treatment.
Dogs that are severely affected may require x-rays or a CT scan to evaluate the ear canal (figure 4). If the ear canal cartilage is no longer bendable and has become calcified, surgery will probably be required.
Figure 4: CT scan of a pug with blockage of the ear canal (green arrow) from chronic infection. The middle ear (red arrow) is filled with fluid and tissue and the bone surrounding it has become thickened.
Dogs that have recurring ear infections that do not respond well to medical treatment should undergo testing of their thyroid gland function and will have their blood chemistries evaluated to see if there is any signs of systemic illness. Additionally, the veterinarian will perform skin scrapes and allergy skin or blood tests to determine if allergies are present.
Differential Diagnoses
Since otitis externa occurs because of other diseases, it is important to rule out the presence of other problems, such as allergies, that predispose the animal to ear infections. Dogs with tumors of the ear or that have had ear canal damage from accidents or animal bites can have signs similar to dogs with ear infections from allergies.
Treatment Options
Medical management is preferred in animals that have inflammation and discharge of the ear canals, but no blockage. The ear canals are cleaned and flushed, and the veterinarian may even need to drain the middle ear to relieve the fluid build up. The animals are treated with a medication that kills mites, bacteria, or yeast, depending on what type of organism is found in the canal. Your veterinarian may also prescribe a short course of steroids to relieve the inflammation and improve drainage of the canal. Some antihistamines may make the animals less itchy, and special shampoos can help treat the rest of the skin. Because pets with ear infections are uncomfortable, pain medications may be prescribed. Some pain medications, such as aspirin, Rimadyl, Deracox, and other nonsteroidal anti-inflammatory drugs should never be used in animals on steroids because the animal can die from intestinal bleeding and perforation. Animals with allergies may require shots or a diet change.
When to Seek Referral
Animals that have a tumor, traumatic separation, calcification, or other blockage of the canal may require removal of the ear canal. This surgery is very complicated and should only be performed by an ACVS Veterinary Surgeon. Find an ACVS Veterinary Surgeon.
Surgeries
Total Ear Canal Ablation and Bulla Osteotomy
When the ear canal is completely calcified or blocked by thickened lining or a tumor, the entire ear canal may need to be removed (Figures 5 and 6). The ear flap is left in place, but may droop a little in dogs with upright ears, such as shepherds. The ACVS Veterinary Surgeon will also need to open the middle ear, or bulla, to remove the lining and provide drainage. Because dogs with otitis externa and media have very thickened and inflamed ear canals, the surgery is may be long and complex and the animal will require pain medication for several days after recovery.
Figure 5. The ear canal is being removed from a pug with chronic otitis externa. Once the canal is removed, the middle ear must be opened and cleaned out.
Figure 6. The final appearance after the skin is closed. The area is being injected with local anesthetic to make the dog more comfortable after surgery.
Vertical Ear Canal Ablation
Occasionally the horizontal portion of the ear canal is normal and only the upright, or vertical portion, needs to be removed. This procedure is less complicated than total ear canal removal and does not require opening and cleaning out the middle ear. Although the ACVS Veterinary Surgeon may plan to perform a vertical ear canal ablation, he or she may find during the surgery that the entire ear canal must be removed because of the extent of the ear canal disease. Lateral Ear Canal Resection (“Zepp”) Procedure
Opening up the side of the ear canal will let more air in, improve drainage, and make it easier for owners to clean and medicate the canals (Figures 7 and 8). Unfortunately most dogs do not show much improvement after this procedure, so it is usually reserved for dogs that are born with narrow ear canals.
Figure 7. The lateral ear canal is opened and a “drain board” is formed from the outer canal wall.
Figure 8. Appearance of a lateral ear canal resection 10 days after surgery. The Q-tip is resting on the new drain board and the horizontal portion of the ear canal sits just above it.
Potential Complications of Surgery
Several important structures are found near the outer ear canal, including the facial nerve and several major arteries. The facial nerve provides sensation and muscle control to the side of the face. This nerve is damaged during surgery in 25-50% of dogs, and in 10-15% the damage is permanent. Affected dogs may be unable to blink after the surgery, and the lip on the damaged side may droop (Figure 9). In most dogs the nerve begins to function after several weeks, but some animals may require eye ointment for the rest of their lives to prevent the eye surface from drying out.
Within the middle ear are the openings to the inner ear, which contains the organs for hearing and balance. The lining of the middle ear must be removed during surgery, and these openings can be damaged. Some animals, particularly cats, may have head tilts after surgery, because of the loss of balance. Since most animals with severe otitis externa have poor hearing before surgeries, owners often do not notice much difference in their dog’s hearing ability after surgery.
The lining in the ear canal and middle ear produces secretions that keep the surfaces moist and healthy. These linings must be removed completely or the animal will develop sores that drain fluid after the surgery site has healed. Some ear tumors cannot be completely removed. Radiation therapy may be recommended to try and slow the growth and spread of the remaining tumor cells.
Figure 9. Facial nerve paralysis and a head tilt. Because of severe ear canal inflammation, this pug had damage to the facial nerve and inner ear before surgery. His lip and tongue drooped on the left side, and he required eye ointment because he could not blink. His head was also tilted to the left. These changes were permanent.
Aftercare
Some dogs will have drains in the surgical site that require bandaging after surgery. Antibiotics may be prescribed if severe infection is present. Sutures will be removed 10-14 days after surgery. Medical management of underlying diseases, such as allergies or poor thyroid function, will need to be continued for life to prevent clinical signs from recurring.
Prevention and Prognosis
Owners of certain breeds of dogs, such as Cocker spaniels, should be prepared for ear problems. These dogs should have their ears checked once or twice a year, and any ear infections should be treated promptly to prevent inflammation and thickening of the canal. Any dogs prone to skin or food allergies should also be checked annually.
Prognosis for surgical treatment of otitis externa and media depends on the underlying cause of the disease. Total ear canal ablation with bulla osteotomy is successful in resolving the drainage and discomfort from the ear in 90-95% of dogs, but problems can recur if underlying allergies or disease are not controlled. Long term success rates are much poorer when lateral ear canal resections are performed on animals that have severely diseased ear canals.
— Karen Tobias, DVM, MS
Diplomate ACVS
Posted 3/28/2006
Reviewed 9/15/2009 by Mitchell A. Robbins, DVM, Diplomate ACVS
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