Otitis Interna and Media in Dogs

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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

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