Middle and Inner Ear Infections in Dogs

Anatomy of a Dog’s Middle and Inner Ear

To better understand why the symptoms of middle and inner ear infections in dogs include neurological signs, let us first tackle the basic anatomy of the middle and inner ear.

Tympanic Membrane

The tympanic membrane or eardrum separates the outer part of the ear canal from the middle and inner ear. It acts as a “wall” that prevents the entry of foreign substances into the more sensitive parts of the ear.

The eardrum is very fragile. It can be damaged during ear cleaning or by ear disease. If the eardrum is damaged, such as when it’s perforated, torn, or ruptured, bacteria and fungi from the external ear canal can enter the middle ear and cause an infection. Inflammation in the middle ear may eventually lead to otitis interna.

Middle Ear

The middle ear is an air-filled cavity where you can find the 3 smallest bones of the dog’s body, known as the stapes, malleus, and incus, which are important in hearing. The Eustachian tube extends from the bulla (air-filled cavity) to the back of the dog’s throat. Air enters the Eustachian tube into the middle ear to balance the pressure against the tympanic membrane (eardrum).

Inner Ear

The inner ear is responsible for maintaining the dog’s balance or equilibrium. This can be achieved with the help of the semicircular canals which are filled with fluid. Nerves that connect to the brain can also be found in the inner ear.

Symptoms of Middle and Inner Ear Infections in Dogs

The symptoms that are exhibited in dogs with otitis media or interna will depend to a large extent on the severity and extent of the infection. There may be no visible symptoms in mild cases, but the more serious infections can affect the nervous system, leading to neurological symptoms.

If symptoms are present, these may include:

• Pain when your dog opens his mouth
• Reluctance to chew
• Head-shaking
• Pawing and scratching of the affected ear
• Redness of the ears
• Ear discharge
• Bulging eardrum (tympanic membrane) when there is a buildup of pus in the middle and inner ear
• Vomiting

If the eardrum has ruptured, signs may also include the following:

• Thick ear discharge that may appear pus-like or bloody
• Sudden loss of hearing
• The ear canal is red and inflamed
• The ear is painful to the touch

When the infection spreads to the internal ear, otitis interna is characterized by:

• Head-tilting towards the affected ear
• Balance problems
• Incoordination
• Pupils are unequal in size
• Involuntary eye movement (nystagmus)
• Paralysis or inability to blink when there is damage to the nervous system
• Deafness may be present when both ears are affected

Causes of Ear Infections in Dogs

The primary cause of ear infections in dogs is bacteria. Other disease-causing agents include yeast or fungi (Malassezia or Aspergillus) and ear mites.

Some factors can increase a dog’s predisposition to infections in the middle and inner ear. These include trauma, tumors in the ear, or the presence of foreign bodies (foxtail or awn) in the ear.

How Middle and Inner Ear Infections are Diagnosed in Dogs

In addition to a thorough medical exam, there are specific diagnostic procedures that can be performed.

About half of the dogs suffering from chronic otitis externa are found to be suffering from an infection of the middle ear. It is often difficult to get a definite diagnosis if the dog’s eardrum is intact.

If the eardrum appears to be bulging or discolored, your vet may puncture it with a sterile needle so the discharge that has accumulated can flow to the outer ear passage and be cleaned up. This can also help relieve the pressure and the pain in the middle ear.

Your vet may get a swab of the discharge for culture to identify the underlying culprit - whether it’s bacteria or yeast or both, and the specific species so the right medication can be given.

Dogs that are prone to ear infections will benefit from a regular exam for any red flags that indicate a potential ear problem. This will allow early diagnosis so appropriate treatment can be given as soon as possible.

A ruptured eardrum or a middle ear infection can be diagnosed when your dog undergoes a medical checkup by your vet. Your dog may need to be sedated or anesthetized to allow a thorough ear exam.

• Myringotomy - This technique involves inserting a sterile needle into the eardrum membrane to obtain a sterile fluid sample from the middle ear for culture and analysis. This can help determine if any infection is present.
• Radiographs - X-rays of the skull can help determine the severity of a middle ear infection.
• Analysis of the cerebrospinal fluid (CSF)
• Urinalysis
• Blood Tests
• Computed Tomography (CT) scan
• Magnetic Resonance Imaging (MRI) scan

Can my dog recover from a middle or inner ear infection?

The prognosis is good for the majority of patients whose ear infections are without serious complications. Even without surgery, most ruptured eardrums heal without surgical intervention.

However, dogs with chronic inflammation in the middle ear that has led to the rupture of the eardrum have reduced chances of successful treatment. If nerves in the ear are affected, neurological signs may persist even after the infection has cleared up.

If there is severe nerve damage, there may be permanent neurological defects in the dog’s face, eyes, and/or lips. There may also be partial or total loss of hearing.

Middle and inner ear infections often require long-term antibiotics or antifungal medications (about 6-8 weeks). Frequent visits to the vet for rechecks and follow-up care are necessary to monitor the patient’s response to medication and ensure the infection is resolving and the eardrum is healing as it should.

It is extremely important that you follow the instructions of your vet to ensure proper healing without serious complications.

Read more:

Causes of Fainting and Dizziness in Dogs

Vestibular Disease in Dogs

10 Facts About Your Dog’s Ears

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