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.