Nystagmus in Dogs
Nystagmus is a condition defined by the involuntary and rhythmic oscillation of the eyeballs; that is, the eyes unintentionally move or swing back and forth. Nystagmus can occur in both dogs and cats and is a characteristic sign of a problem in the animal's nervous system.
Symptoms and Types
There are two types of nystagmus: jerk nystagmus and pendular nystagmus. Jerk nystagmus is characterized by slow eye movements in one direction with a rapid correction phase in the opposite direction, while pendular nystagmus is characterized by small oscillations of the eyes with no movement being distinctively slower or faster than the other. Of these two types, jerk nystagmus is more commonly seen in dogs. Other common signs associated with nystagmus include head tilting and circling.
There are a variety of causes that may lead to nystagmus, many of which stem either from a peripheral vestibular or central vestibular disease. Sometimes called the “balance system,” the vestibular system is the sensory system responsible for maintaining proper balance of the head and body.
Peripheral vestibular diseases that may lead to nystagmus include hypothyroidism, traumatic injuries (such as those acquired in a car accident), and neoplastic tumors. Nystagmus-causing central vestibular disorders include tumors, thiamine deficiency, viral infections (such as canine distemper), and consequent inflammation, heart attacks, hemorrhages in the heart, and exposure to toxins (such as lead).
Nystagmus is often diagnosed via an analysis of cerebrospinal fluid, which can also reveal inflammation associated with the disorder. Brain imaging (e.g., CT scan) is another diagnostic procedure used to identify brain abnormalities. Otherwise, your veterinarian may conduct analysis on the urine and bacterial cultures and serologic testing to check for infectious agents in the body.
Treatment and care varies and is entirely dependent upon the underlying cause of the disorder and the severity of symptoms. In general, if a central vestibular disease (rather than a peripheral vestibular disease) is diagnosed, more intensive care will be required.
For dogs experiencing anorexia and vomiting, fluid therapy (including the administration of fluids through IV) may be necessary to prevent dehydration. Your veterinarian may also prescribe certain types of medication depending on the diagnosis.
Living and Management
Post-treatment care is dependent on the cause diagnosed as well. However, most veterinarians recommend a neurologic exam approximately two weeks after initial treatment to monitor for improvement or progression of the disease. Secondary symptoms, such as dehydration due to excessive vomiting, should also be monitored and addressed.
Prognosis varies, but dogs with a peripheral vestibular disease rather than a central disease tend to have a better prognosis with improved chance of recovery.
Because there is such a wide variety of causes that may lead to nystagmus, there is no distinct method of prevention. However, keeping your dog safe indoors without access to lead and other toxic materials, is recommended.