Otitis Interna and Media in Dogs

Overview of Canine Otitis Interna and Otitis Media

Below is an overview of internal and middle ear infections in dogs followed by in-depth information on the diagnosis and treatment of this serious condition.

A dog’s ears are responsible for taking sound waves from the air and transporting them to the brain. These waves pass through the ear canal until they come in contact with the nerves that convert them into sound and allow for hearing.

The ear canals are divided into three sections; the external, middle and internal parts. The external ear canal extends from the outside of the ear lobe to the eardrum. The middle ear begins with the eardrum and includes the bones and nerves of the ear. The inner ear is closest to the brain and contains the organs responsible for maintaining proper position.

If the inner ear is not functional, the animal feels dizzy and the brain is not able to determine if he/she is standing, turning, lying down, spinning. The most common abnormality associated with the middle and inner ear is inflammation, which is referred to as otitis media or otitis interna. Otitis is the Latin term for inflammation within the ear. Media and interna refer to the parts of the ear that are inflamed. Otitis externa refers to an external ear canal inflammation or infection.

Inflammation within the ear can have numerous causes including bacteria, fungi, yeast, parasites, foreign objects, trauma, polyps and cancer. Middle ear infections typically occur in association with external ear infections. Inner ear infections can then occur as a progression of a middle ear infection. For this reason, prompt diagnosis and treatment of external ear infections can significantly reduce the chance of a middle and/or inner ear infection.

Deafness is a possible permanent effect if otitis media/interna is not treated appropriately. Signs of middle and inner ear inflammation vary depending on which part of the ear is affected and the severity of the infection.

What to Watch For

• Head shaking
• Pawing, rubbing at the ear
• Discharge from the external ear canal
• Pain when the head is touched
• Pain with the mouth is opened
• Depression
• Loss of hearing
• Lack of appetite
• Head tilt
• Circling
• Leaning to one side
• Rolling
• Stumbling
• Vomiting
• Side to side involuntary continuous eye movement (nystagmus)

Diagnosis of Otitis Interna/Media in Dogs

Otitis media and otitis interna are usually diagnosed based on results of a physical examination and thorough ear exam. Finding the exact cause of the ear inflammation requires more tests and may include:

• Complete blood count (CBC) and biochemical profile to determine the overall health of the animal
• Sedation or anesthesia for a thorough examination since the ear may be quite painful
• Radiographs of the skull and base of the ear, although not usually helpful, to look for tumors or masses at the base of the ear
• Culture and cytology of any discharge or fluid within the canal to determine the cause of the inflammation. Culture can detect bacterial causes and help determine the appropriate antibiotic treatment. Cytology can detect parasite, fungus, yeast and some cancers.

Treatment of Otitis Interna/Media in Dogs

The goal of treatment for otitis media or otitis interna is to remove the cause of the inflammation and provide ventilation and drainage. Treatments vary depending on the cause of the inflammation and may include:

• Initial flushing of the ear canal with warm saline (salt water solution)
• If the eardrum is intact, a puncture through the eardrum to alleviate the pain and pressure as well as drain the middle and inner ear. This is painful and is done under anesthesia.
• Flushing the middle ear after perforating the eardrum
• Removal of any foreign object
• Oral antibiotics for 3-6 weeks for bacterial, fungal and yeast infections

Ear medications must be used cautiously, if at all. Usually, flushing the ear and oral antibiotics resolves the infection. For parasitic causes of inflammation, ear medications may be necessary.

If the infection is resistant to treatment or if polyps or cancer is the cause of the inflammation, surgery may be necessary. Surgery is more likely if the inflammation has progressed to include the inner ear.

Home Care and Prevention

There is no home care for otitis media or otitis interna. See your veterinarian if your pet is showing signs of a middle or inner ear infection.

Prompt and thorough treatment of external ear infections can greatly reduce the risk of otitis media and otitis interna.

For dogs that hunt or spend time in wooded areas, frequent ear exams looking for foreign objects such as grass awns can help reduce the chance of foreign body induced otitis media/interna.

Information In-depth on Internal and Middle Ear Infections in Dogs

Otitis media and otitis interna are defined as inflammation within the middle and inner ear. There are a variety of causes such as bacteria, fungi, yeast, parasites, foreign object, trauma, polyps and cancer.

Otitis media and otitis interna are usually caused by an extension of an external ear infection. It has been estimated that 50 percent of chronic external ear infections progress to middle ear infections.

Inner ear infections are usually a progression from middle ear infections but can develop from the spread of bacteria through the bloodstream. In these cases, an inner ear infection may not be associated with a middle or external ear infection.

Causes of Otitis Interna/Media in Dogs

• The most common cause of otitis media/interna is bacteria. Various bacterial agents have been recognized in middle/inner ear infections.
• Fungi and yeast are common causes of external ear infections but are not commonly found in the middle/inner ear. Malassezia, Aspergillus and Candida are some fungi/yeast involved in ear infections.
• The most common parasite is the ear mite, which is usually associated with middle/inner ear infections in cats.
• Foreign objects usually only affect one ear. Plant or grass awns are commonly the cause, but other foreign objects such as fleas, small insects or grass can also cause middle/inner ear inflammation.
• Trauma is not a common cause since the middle and inner ear are well protected with a bony covering.
• Polyps can originate in the middle ear, push through the eardrum and can be seen in the external ear canal.
• Various types of cancer have been found in the middle and inner ear. For the middle ear, squamous cell carcinoma, fibrosarcoma and lymphoma are most common. For the inner ear, neurofibrosarcoma, meningioma and carcinoma are possible.

Diagnosis In-depth

Diagnosing otitis media/interna can be accomplished with physical exam findings. Sometimes, sedation or anesthesia may be required to fully examine the ear if the pet is too painful.

Since most middle/inner ear infections are progressions of an external ear infection, extensive flushing and cleaning of the external ear canal is frequently necessary before exam of the middle ear.

Some polyps can be diagnosed based on examination. The polyp may begin in the middle ear, push through the eardrum and be visualized in the external ear canal.

If the eardrum is bulging, it may need to be punctured or perforated in order to collect and analyze fluid within the middle ear. This procedure is referred to as a myringotomy and is performed under anesthesia.

The fluid within the middle ear is collected and analyzed. Culture of the fluid may reveal bacteria. Cytology (microscopic exam of the fluid and discharge) may reveal fungi, yeast, parasite or cancer cells.

Treatment In-Depth

Once the cause of the otitis media/interna has been determined, treatment can begin and includes:

• If the eardrum is not ruptured, it will need to be punctured to alleviate pain and pressure and allow for drainage of any built up fluid. Once the eardrum is perforated, the middle ear is flushed. After this procedure, about 50% of patient’s eardrum heal.
• Oral antibiotics are typically administered for 3-6 weeks.
• Ear medications are only used if absolutely necessary. Using ear medication without an intact eardrum can result in permanent deafness or signs of an inner ear infection (dizziness, head tilt, vomiting).

If no improvement, surgery is the next option. There are various surgical procedures performed to treat middle and inner ear infections. The severity of the infection will determine which procedure is chosen.

Lateral Ear Resection

This procedure is done if the primary problem in an external ear canal that does not adequately dry. Chronic external ear infections can lead to middle ear infections. By removing a portion of the external ear canal, the remaining canal is wider and easier to dry. This can reduce external ear canal infections and therefore, reduce middle ear infections. The patient typically does not lose hearing as a result of this procedure. (The patient may have already become deaf from chronic infections)

Lateral Bulla Osteotomy

This procedure involves entering the middle ear through an incision on the side of the ear base and penetrating into the bone surrounding the middle ear. Once the middle ear cavity is entered, it is flushed and a drain is placed until the infection is under control. Some animals may still be able to hear following this procedure.

Total Ear Canal Ablation

This is the most severe surgery where the entire ear canal is removed. This is a salvage procedure and done when no other treatment is effective. Following this procedure, the patient is deaf.

Follow-up for Dogs for Dogs with Otitis Interna/Media

After treatment, periodic exams are necessary to reduce the risk of future infections and to make sure the current infection is responding to treatment. Make sure your pet’s ear canals are kept clean and dry.