Most mammals gain their sense of balance and spatial orientation from organs in the inner ear and parts of the brain, collectively called the “vestibular system”. If the vestibular system becomes diseased, this affects the ability of the animal to balance itself. There are two forms of vestibular disease. The most common form is peripheral vestibular disease which arises from disorders affecting the inner ear and nerves (i.e. not the central nervous system). The second form, called central vestibular disease, is a much less common condition although it is considerably more serious as it originates within the central nervous system. Both forms result in the animal experiencing a loss of balance and other symptoms of vertigo and dizziness. This disease can appear extremely dramatic to dog owners, particularly the first time the symptoms are observed. However, most cases improve quickly with appropriate care, treatment and addressing the causes of the condition.
Peripheral vestibular disease
Peripheral vestibular disease results from irritation of the nerves connecting the inner ear to the brain. This irritation can arise from several causes:
• Chronic and recurrent infections of the inner and middle ear
• Overzealous cleaning of the ears
• Trauma from head injury
• Drugs like the aminoglycoside antibiotics, including amikacin, gentamicin, neomycin and tobramycin.
• Loop diuretics
• Ear cleaners that should not be used with ruptured eardrums
• Congenital defect (present from birth)
Peripheral vestibular disease can also be idiopathic, meaning the cause has not been identified. Infection of the middle ear is the most common cause of the disease in younger dogs; in older dogs, brain tumors may be the cause of the disease.
Central vestibular disease
Causes of central vestibular disease include:
• Inflammatory disease
• Bleeding in the brain
• Loss of blood flow
SIGNS AND SYMPTOMS
Signs of vestibular disease include:
• Abnormal posture, e.g. leaning or head tilt (towards the side of the problem)
• Asymmetric ataxia, i.e. “drunken” gait (worse on the side of the problem)
• Circling/deviating (towards the side of the problem)
• Nystagmus – involuntary, rhythmic, jerking eye flicks – the slower flick is towards the side with problem)
• Vomiting (motion sickness)
Dizziness and loss of balance can cause excessive drooling, sometimes with nausea and vomiting. If only one ear is affected, circling and head-tilting is usually in the direction of that ear and only the eye on that side may develop nystagmus.
Congenital vestibular disease is usually apparent before 3 months of age. Breeds that are predisposed to this condition include the Akita, Beagle, Doberman pinscher, German shepherd, English cocker spaniel, Smooth fox terrier and the Tibetan terrier.
Vestibular disease in old dogs is often mistaken for the animal having a stroke. The signs of vertigo caused by the disease can be more intense in older dogs which may show a complete inability to stand, nausea and circling. The disease in old dogs can make eating and drinking, or even going outside to urinate or defecate, very difficult, if not impossible. Therapy is likely to be needed in the form of intra-venous fluids and supplemental nutrition.
A physical examination and neurological assessment will ascertain if the vestibular disease is of the peripheral or central form. If the peripheral form of the condition is identified, your veterinarian will likely use an otoscope to look deep into your pet’s ears. Sometimes, x-rays are needed to assist the diagnosis. Other screening methods such as blood tests, culture and sensitivity, and cytology will help eliminate other potential causes of specific symptoms. Your veterinarian may also recommend a biopsy of any polyps or tumors that are found. If central vestibular disease is diagnosed, MRI or CT scans are likely to be recommended. Additional tests include cerebrospinal fluid analysis in which the fluid that bathes the brain and spinal cord is analyzed for abnormalities in protein concentration, cell counts and other parameters. This test is most useful to determine if there is an inflammatory and/or infectious disease.
The aims of treating vestibular disease are two-fold. The first aim is to deal with the underlying cause while the second aim is to provide supportive care.
The symptoms of nausea and vomiting can be mitigated by motion sickness medications. If the middle or inner ear is infected, antibiotics are likely to improve the condition. Ear infections should be identified and treated as quickly as possible. Inflammation may respond to treatment initially, but without good treatment, it can progress to a point where it may be untreatable. If the vestibular disease is caused by an under-active thyroid, the condition will resolve once the metabolic condition is managed correctly. If a medication is the cause, stopping the medication can bring complete resolution, however, there can sometimes be some residual hearing loss. Surgical removal of polyps can result in a complete cure, however, if there are cancerous tumors, the prognosis is usually less positive. The central vestibular form of the disease generally has a poorer prognosis than the peripheral form, primarily due to the potential for devastating damage to the brain stem. Fortunately, most cases of the peripheral form improve quickly once the underlying cause is diagnosed, addressed and the vertigo symptoms are treated with appropriate care.
Rehabilitation therapy can help your dog learn better awareness of his body position and thereby improve his stability. Symptoms of dizziness can prevent, or even totally stop, normal walking. This means food and water sometimes need to be close to your pet, or even brought to him to eat or drink. Some dogs may need to be hand-fed for a while. Many dogs need help getting to a place for urination or defecation.
There is no treatment that consistently manages either congenital vestibular disease or the geriatric condition. These pets require nursing care and confinement. Puppies born with the congenital disease often adapt and are less affected as they get older. In old dogs, the condition usually resolves in 7 to 14 days, however, the head-tilt can be life-long.
Talk to the veterinarian if you are concerned your pet is showing signs of vestibular disease.