Vestibular Disease in Dogs

The term vestibular refers to the inner ear organs of the body.  Vestibular disease in dogs is not a true “disease” as such but actually is a composite of various neurologic signs that occur as a result of a malfunction of some part of the vestibular system.  This system is responsible for the maintenance of balance and the coordination of position of the head, eyes, neck and limbs in space. It can be either peripheral (PVD) or central (CVD) in nature and can be the result of a vestibular lesion or other disease like hypothyroidism (low thyroid function) or hyperadrenocorticism (abnormal excessive presence of adrenocortical hormones, especially cortisol in the body).  Both types of this condition usually present with acute onset (suddenly) and a peripheral vestibular issue may follow a recent ear infection.

Vestibular disease is defined as the sudden, non-progressive disturbance of balance.  It is also known as old vestibular syndrome and canine idiopathic vestibular syndrome. It is usually found more often in older dogs than in younger ones.

This condition will likely present suddenly and can be central or peripheral in nature.  The primary and most noted symptoms are:

• Head tilt to one side or the other
• Vestibular ataxia (lack of muscle control) often asymmetric (not equal on both sides)
• Tight circling, falling or rolling
• Spontaneous nystagmus (rapid involuntary eye movements)
• Nausea and vomiting similar to that of motion sickness
• Strabismus (misalignment of the eyes or the condition of having a squint)
• Disorientation
• Reluctance to walk or stand
• Leaning or falling in the same direction as the head tilt    

The most likely symptoms that you will note in your pet in regard to CVD:

• Depressed mental state in which the animal displays disorientation and poor interaction with other animals and humans
• Postural defects like the loss of normal strength and proprioception (the sense of knowing where your joints are in space or body awareness)

The symptoms that will likely be most obvious to you, the owner, will be the head tilt and vestibular ataxia noted above.  Seek medical care as soon as possible when these symptoms are noted.

Types 

Vestibular disease is generally a condition that affects older dogs and is usually peripheral or central in nature.  There are several types: 

• Peripheral vestibular disease (PVD) usually produces leaning in one direction and increased resting nystagmus - this type involves the ear and nerves
• Central vestibular disease (CVD) usually produces a non-ambulatory animal with decreased resting nystagmus - this type involves the brain
• Congenital peripheral or central vestibular disease is very rare in puppies

The dysfunction is more common in older dogs but can be secondary to a neoplastic lesion.  The head tilt and positional strabismus is pretty much equal in regard to the symptoms noted in your pet in both types of vestibular disease in dogs.

There are a number of known or suspected causes of vestibular disease.  Some of these causes are more serious than others and will require some sort of medical assistance or intervention to resolve.

• Middle ear or inner ear infections
• Drugs that are toxic to the ear, for example Metronidazole
• Trauma or injury
• Tumors (neoplasia)
• Hypothyroidism
• Vascular disease, for example, stroke - though a rare cause

Depending on the actual cause of the episode, after a fairly fast onset of the clinical signs mentioned above, there could be a period of relatively rapid improvement of those symptoms and signs with minimal if any medical intervention having been required.

Diagnosing this disease will require a neurological examination by your local veterinarian.  He or she will need to determine if the vestibular issue is peripheral or central in nature.  Here is what he or she will be looking for in the physical neurological assessment:

• CVD - Vestibular signs like body awareness on one side only, unilateral paresis (paralysis), altered mental status, cranial nerve deficits (especially those related to cranial nerve V and VII)
• PVD - Vestibular signs like body awareness as above, normal strength, normal mental status, cranial nerve deficits (cranial nerve VII and Horner’s only)

There will likely need to be some diagnostic testing done as well:

• MRI of ears and brain
• CT scan and radiographs - ear infections are better seen and assessed via these imaging methods
• Blood pressure testing
• CSF (cerebrospinal fluid) analysis to help in the determination of the presence of inflammatory or infectious disease
• Testing for viruses versus protozoa
• Myringotomy (surgical infusion into the ear drum to relieve pressure or drain fluid) for middle ear infections
• BAER (Brainstem Auditory Evoked Response) to evaluate the hearing channels and pathways which are in close proximity to the vestibular pathways

The treatment of vestibular disease in dogs is twofold:

The underlying or root cause of the disease needs to be determined and treated. Your veterinarian will need to identify the possible cause so that she can develop a treatment plan. 

Supportive care comes into play as well in the form of things like:

• Intravenous fluids if your dog is dehydrated
• Anti nausea medication to prevent or limit vomiting
• The administration of a medication called propentofylline to hasten the brain’s natural ability to compensate after any unilateral vestibular damage occurs
• Close monitoring of your pet during treatment
• Antioxidants and essential fatty acids to assist the body’s healing powers
• Quiet environment if the nystagmus persists or if it goes away and then returns

Research has revealed that there is some experimental benefit to be gained from the use of the medication propentofylline in rats as it has shown some increasing of the speed at which the brain is able to compensate after unilateral vestibular damage.  If this medication option is utilized, then it will, of course, require close monitoring of your pet during treatment.

Additionally, the nystagmus can make an occasional return suddenly and last for a brief period of time.  If your pet experiences this symptom reappearance, you should keep your pet in a quiet environment during that period of time and you should monitor him closely.  If the nystagmus persists, then your veterinarian will need to re-examine and re-investigate the physical condition of your companion. Depending on the cause and the type of vestibular disease identified, the end result could be permanent damage in which your beloved family pet displays a permanent head tilt, balance issues, and disorientation. There may be adjustments needed in the home environment and by the family to deal with any permanent physical or neurological damage following vestibular disease, in order to keep him safe.