A closer look: Involuntary Eye Movement (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.
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Nystagmus is associated with about one hundred conditions. The most common cause is Old Dog Vestibular Syndrome (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.
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.
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.