Involuntary Eye Movement (Nystagmus) in Dogs

Key Takeaways

Nystagmus is rhythmic involuntary movement of the eyes. It presents as a rapid horizontal or rotatory twitch. 

• In most cases nystagmus is an indicator of a vestibular system disease, especially if it appears alongside other symptoms such as loss of balance and head tilting

• Can also be a sign of ear infection, other infectious diseases, toxins, or tumors

• Often appears suddenly and in an acute form

• Jerk nystagmus is the most common in dogs and indicates a vestibular dysfunction

• Physical exam, blood work, urinalysis, and diagnostic imaging may be used to determine underlying cause

• The most common associated conditions are non-life-threatening and most dogs recover fully

• Treatment and prognosis depend on the underlying condition

A Closer Look: What is Nystagmus in Dogs?

Nystagmus is most commonly an indicator of Old Dog Vestibular Syndrome (ODVS) which is usually not life threatening. It’s common to think an old dog who suddenly develops nystagmus and trouble walking has had a stroke and is at the end of his life, but this is generally not the case. Nystagmus is associated with various other diseases, most of which are non-life-threatening. If the symptom appears suddenly it is always better to seek veterinary care as it could be an indicator of central nervous system malfunction or brain injury.

Note: It is normal for nystagmus to occur when the head is moving. To assess the symptom it has to be observed when the animal’s head is in its neutral extended position.

Possible Causes

Nystagmus is associated with about one hundred conditions:

• The most common cause is ODVS, a spontaneously occurring disease that causes loss of balance, difficulty walking, and circling. ODVS runs its course in a relatively short time (about two weeks) after which most dogs fully recover

• Another possible diagnosis is a middle or inner ear infection, especially if there is a previous history of ear infections.

• Other infectious diseases such as babesiosis can also cause nystagmus

• Brain tumor or brain injury

• It can also be a sign of the presence of toxins in the body like bromethalin (often found in rat baits), ethylene glycol (commonly found in antifreeze), and THC.

Risk Factors

The most common form of this symptom is jerk nystagmus, characterized by a slow phase where the eyes move slowly in one direction, and a quick phase where they return fast to the original position. This type indicates a vestibular dysfunction. Pendular nystagmus occurs without noticeable variations in the eye movement’s speed. This second type is less common in dogs.

Testing and Diagnosis

When presented with nystagmus, a veterinarian runs several tests to check whether the cause is a brain abnormality or infectious and determine the overall health status of the dog:

• Physical exam • Blood work • Diagnostic imaging

Advanced diagnostic imaging and analysis of cerebrospinal fluid may be indicated in some cases. Referral to a neurologist is sometimes recommended. Older dogs presenting with sudden onset nystagmus along with ataxia and circling may be presumed to have ODVS, delaying a diagnostic workup until they fail to improve or get worse. 

Treatment varies depending on the underlying condition and the severity of the symptom. Some dogs with nystagmus get better without treatment, while some underlying conditions are much more serious and difficult - if not impossible - to treat.

Similar symptoms

A dog with nystagmus or who is experiencing ODVS is often incorrectly referred to as having a stroke, but this is not usually the case.

Associated Symptoms

Nystagmus is often seen alongside:

• Head tilt • Circling • Difficulty rising • Difficulty walking • Loss of balance • Loss of orientation

• Lack of coordination (ataxia)