There are many possible causes of peripheral vestibular disease in the cat.
Otitis – Ear infection is a common cause of peripheral vestibular disease that affects your cat’s health. These infections typically begin as mild infections affecting only the outer portions of the canal (called otitis externa). If symptoms are not seen or ignored, more serious complications often occur. The infection will rupture the protective tympanic membrane (ear drum). Called otitis media, this more severe manifestation is much more challenging to treat and has more serious complications. Least of all, but not to be overlooked, is pain. This author was diagnosed with otitis media after an incapacitatingly painful episode, so timely treatment is very important. The most concerning is long term potentially irreversible changes to the ear canal and nervous system.
Infection caused by bacteria, yeast, or rarely fungus and mites causes a cascade of inflammatory reactions with the immune system of the body. The body’s white blood cells’ killing of these invaders creates fluid, debris, swelling and inflammation in the ear canal. These byproducts affect both the fluid (endolymph) and the hair cells’ ability to assess changes in gravity and balance, thereby leading to the clinical signs of head tilt, leaning, falling, and nausea.
Idiopathic – This term means there is a recognized syndrome of vestibular disease that does not have an identified mechanism. This manifestation of vestibular disease in the cat is somewhat different than the dog. It is seen more commonly in outdoor cats in summer and fall, and seen at a higher incidence in the northeast U.S. and mid-Atlantic states. There is growing evidence to suggest that this, different than the dog, is closely related to vestibular neuritis in humans. The cause is suspected to be an immune-system reaction to viral pieces (antigens) in the body. The cat version of this disease presents bilaterally (both sides affected) much more commonly than dogs.
Some have suggested that blue-tail lizard (Plestiodon fasciatus) ingestion may be a cause of vestibular disease in cats. This theory has gained little traction as idiopathic vestibular disease is seen much more commonly in regions where these lizards do not live.
Burke E.E., Moise N.S., deLahunta A., et al: Review of idiopathic feline vestibular syndrome in 75 cats. J Am Vet Med Assoc 187. 941-943.1985
Polyps – Polyps are growths from the cells lining the ear canal and mouth. These are extremely rare in dogs but not uncommon in cats, especially ages 1-5 years of age. They are most often seen on one side only. One may notice signs of an upper respiratory infection (sneezing, ocular and nasal discharge) in addition to the vestibular signs mentioned previously.
Lorenz, M. Handbook of Veterinary Neurology. Saunders, Philadelphia. 2004
Tumors – There are a variety of tumors that cats can get in their ear canals. Clinical signs are seen due to pressure from the growth of a mass on the vestibular apparatus, or invasion from abnormal cells. Unfortunately, upwards of 85% of aural (ear) tumors are malignant. Treatment is typically surgical removal, and concurrent radiation therapy may offer additional therapeutic value. If advanced imaging (CT/MRI) shows boney destruction into the canal/skull, cancer is a higher likely diagnosis.
Toxins – There are a number of items that are toxic to the vestibular apparatus. Ironically, some antibiotics used to treat ear infections may be toxic. In addition, there are a number of drug classes ranging from diuretics (like furosemide), to antidiarrheals (notably metronidazole at high chronic doses), to chemotherapy agents (platinum derivatives). Many topical ear cleaners contain products that are toxic to the ear. It is important to note that many of these products, especially topical ones, are only toxic in the absence of a functional tympanic membrane (ear drum). This underscores the importance of a veterinarian’s exam to evaluate all of these factors.
Congenital Vestibular Disease – Oriental breeds such as Siamese, Burmese, and Tonkinese cats have a predisposition to congenital vestibular disease. Clinical signs such as a head tilt or difficulty walking are usually apparent early in life. While many times the cause is unknown, the prognosis is favorable. Some cats resolve their signs as they age, while others have residual head tilts or other subtle neurologic deficits. Many cats will leave a fairly normal life with this affliction. As an aside, some will define these syndromes as central vestibular disease.