What is otitis interna?
Otitis interna is inflammation of the inner ear, most often caused by an infection. The infectious agent is most commonly bacterial, although fungus (yeast) can also be implicated in an inner ear infection.
If your dog has ear mites in the external ear canal, they can ultimately cause a problem in the inner ear and create a greater risk of bacterial infection. Similarly, inner ear infections may develop if there is disease in one ear canal or when a benign polyp grows from the middle ear. A foreign object, such as a grass seed, may also cause a bacterial infection in the inner ear.
Are some dogs more susceptible to inner ear infections?
Yes – dogs with long, heavy ears seem predisposed to chronic ear infections that can lead to otitis interna. Any dog with a chronic, hard-to-control ear infection may develop otitis interna if the tympanic membrane (eardrum) is damaged, as the damaged eardrum allows bacteria to migrate into the inner ear.
Excessively vigorous cleaning of an infected external ear canal can sometimes cause otitis interna. Some ear cleansers irritate the middle and inner ear and can cause signs of otitis interna if the eardrum is damaged, allowing some of the solution to penetrate too deeply.
What are the clinical signs of an inner ear infection?
The signs of otitis interna depend on the severity and extent of infection. Common signs include:
- Reluctance to chew or seems to be in pain when opening the mouth
- Shaking the head
- Pawing at the affected ear
- A head tilt, usually to the side of the infected ear
- Leaning, falling, or rolling toward the infected side
- Lack of balance, making walking difficult - may walk in circles toward the side of the infected ear
- If both ears are involved, the dog may swing their head from side to side and have difficulty staying on their feet
- Lack of hearing on the affected side
- Vomiting and nausea
If the facial nerve is damaged by an inner ear infection, your cat may develop some of the following symptoms:
- Drooling from the side of the mouth
- Difficulty eating, dropping food
- Inability to blink
- Dry eye in the unblinking eye
- Eye discharge
- Drooping eyelid, lip, and nostril on the affected side
- Symptoms of Horner’s syndrome, which include anisocoria (the pupil is smaller on the side of the infected ear), prominent third eyelid, and drooping upper eyelid on the affected side
- With long-term facial nerve paralysis, the face may twist toward the side of the ear infection
Additional signs may include:
- Redness in the affected ear
- Discharge with a foul odor
- Thickening and hardening of the outer ear canal due to chronic inflammation
- Enlargement of the lymph node at the base of the chin on the affected side
- Reluctance to move, preferring to sit or lay in one spot
- Swinging the head from side to side, even at rest
- Short, rapid side-to-side movements of the eyeballs (nystagmus)
How is otitis interna treated?
Otitis interna is a serious condition. If your dog cannot eat or drink normally due to nausea or disorientation, hospitalization for intravenous fluid therapy is generally warranted. Nausea must be controlled and dehydration avoided. It may also be necessary to sedate or anesthetize your dog to adequately see the ear tissues, take samples for bacterial culture, and appropriately clean the ear.
Treating the underlying infection. Treatment of the underlying infection is essential, and your veterinarian will prescribe the appropriate medications. Medications may be administered directly in the ear and orally.For bacterial infections, antibiotics are used for a minimum of six to eight weeks, and are ideally chosen based on culture and sensitivity testing on the debris samples from the middle ear. If the infection is fungal, an anti-fungal medication (most often itraconazole) will be prescribed. All medication must be given precisely as prescribed.
Home care during recovery. If your dog’s balance is altered, restrict their activity during treatment to prevent falling injuries. These dogs should not have access to stairs as they may fall. You may also need to temporarily hand-feed your dog, as moving their head down into a dish may stimulate nausea. Anti-nausea medications such as dimenhydrinate (Gravol®) or maropitant (Cerenia®) may be prescribed.
Surgery in some cases. Dogs with otitis interna occasionally require surgery if they have relapses, do not respond to medical management, or deteriorate despite treatment. Surgery is reserved for dogs with:
- Fluid build-up in the middle ear
- Infection of the bone surrounding the ear (osteomyelitis)
- A mass (benign or malignant tumor) arising from the middle ear or the eustachian tube (the tube leading from the middle ear to the back of the mouth).
Surgery may be performed to drain the middle ear cavity or, in severe cases of middle and inner ear infection, the entire external ear canal may also be removed. The severity of the nervous system signs associated with otitis interna does not determine the need for surgery.
Are there any potential complications or long-term effects of otitis interna?
A severe inner ear infection can spread to the part of the brain that controls your dog’s breathing and heart rate, although this is quite rare. Two potential long-term complications of inner ear infection include a permanently altered sense of balance and persistent signs of Horner’s syndrome. Your dog may also become permanently deaf in the affected ear.
Most dogs with otitis interna respond well to medical management. Expect a two to four-month course of oral antibiotics to prevent a relapse. The altered sense of balance that accompanies otitis interna typically improves within two to six weeks.
