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Vestibular Syndrome

Vestibular syndrome in dogs and cats can be a frightening event for owners, given the set of clinical signs that typically present when their pet is affected by this disease. For the owner or even young veterinarian that has little experience with canine and feline vestibular syndrome, it can often be mistaken for a poisoning, siezure, or stroke. In some cases of vestibular syndrome, there is an identifiable underlying cause, but in most cases, it is never really understood what set the disease off. When we are not certain of the pathogenesis of a disease process, we tag it with the term, ideopathic, hence the name of the disease, ideopathic vestibular syndrome. To understand the disease and its implications, it if first very important to understand the vestibular system, its functions, and the organs involved.

The vestibular system accomplishes three tasks. First, it contributes to an individualís sense of equilibrium in relation to the force of gravity and thus adds to the subjective sense motion and spatial orientation. Second, inputs coming from the vestibular system convey information to the body ís muscles and posture. Third, while head and body are in motion, the vestibular system controls eye movements so that images remain steady and in focus. This is called the vestibular-ocular reflex.

These tasks are accomplished through the mechnoreceptors of the three semicircular canals housed within the inner ear, the utricle and the saccule. Like the neighboring auditory system, each canal has hair cells that detect minute changes in fluid displacement, but unlike the auditory system, the utricle and the saccule send information to the brain regarding linear acceleration and head tilt. Likewise, there is a canal that detects head movement in the eye position, and there is yet another semicircular canal that detects motion from moving your head from shoulder to shoulder. These hair cells called stereocilia are located within the crista that is in each semicircular The ultimate carrier of signals from all of these aforementioned organs to the brain, is the vestibular nerve. The vestibular nerve ends at a nerve bundle within the brain stem called the vestibular center. Disease of any part of this system leads to disfunctions in balance, spatial orientation, and overall equillibrium.

As previously mentioned, by far the most common cause for vestibular syndrome remains unknown or ideopathic. However, since the canals and sensitive organs of the inner ear are the sensory input for the vestibular system, inner ear infections are a known cause for vestibular syndrome in dogs and cats, and is therefore a primary rule out when presented with a canine or feline patient showing vestibular signs. The least common cause for canine and feline vestibular syndrome is a tumor on or near the vestibular center of the brain stem.

Vestibular syndrome occurs most commonly in middle to senior age dogs and cats. Clinical signs a dog or cat will likely display in an acute vestibular event are: head tilt, circling, falling, and jerking of the eyes from side to side (nystagmus). The head tilt, circling, and falling are all directed toward the same side, which tells us which side of the body the respective vestibular system is affected. There is also associated vomiting and anorexia.

Once vestibular syndrome is recognized, the veterinarian must throughly examine the ear of the affected side to rule out inner ear infection as a potential cause. If the ear is found to be severely infected, then treatment of the infection must be addressed. The vestibular signs should gradually begin to resolve once the infection is under control.

If the ear is found to be free of infection, then it must be assumed that the vestibular syndrome is ideopathic in origin, or there is cancer. Since cancer of the vestibular system is quite rare, I only revisit that possibility if the patient does not resolve.

Ideopathic vestibular syndrome cannot be treated. However, the course of disease is such that it presents acutely, then gradually resolves on its own over 7 – 30 days. There is no way to speed this recovery process, but during this time the patient needs to tbe supported by antinausea and dizziness medication, and fluids (if the patient is so bad the it cannot eat). In majority of cases, the vestibular signs completely resolve, but with others some remnants of disease never go away. For example, some dogs and cats will keep a mild head tilt and occasionally cirlce, but for the most part, quality of life is good. If the condition does not resolve, then MRI or CT scan should be performed to rule out tumor (s).

Dogs and cats that have recovered from ideopathic vestibular syndrome usually do not ever have it again, but a minority of cases experience relapses. Unfortunately, there is no way to prevent relapses.

Roger L. Welton, DVM
Founder and Chief Editor, Web-DVM.net
President, Maybeck Animal Hospital

Article updated 8/18/2012