SYMPTOM
Nystagmus
Owners may observe nystagmus in their pet.
Various conditions
This symptom can occur in multiple conditions and warrants further assessment.
Peripheral Vestibular Disease (Ear-Related)
Infection or inflammation of the middle or inner ear disrupts the balance signals the brain relies on to hold the eyes steady, producing a horizontal or rotatory jerking eye movement. In dogs this most often follows chronic otitis externa that has progressed inward, while in cats an inflammatory ear polyp is a recognised cause. Head tilt and unsteadiness usually accompany the eye movement.
Idiopathic Vestibular Syndrome
A sudden-onset balance disturbance of unknown cause, sometimes still referred to as old dog vestibular syndrome, is classically a condition of older dogs, but the feline form can affect cats of any age and tends to cluster in the summer months for reasons that are not fully understood. It produces nystagmus, head tilt, and loss of coordination that comes on within hours, is a diagnosis reached once other causes have been excluded, and most animals improve steadily over the following one to two weeks, though full resolution can take a little longer.
Central Nervous System Disease
Lesions affecting the brainstem or cerebellum — from inflammation, vascular events, or tumours — disrupt the same balance pathways as ear disease but from within the brain rather than the ear. Nystagmus of central origin is more likely to be vertical, to change direction with head position, or to occur alongside other neurological signs such as altered mentation or weakness on one side.
Congenital Nystagmus
Some cats, particularly Siamese and other colourpoint breeds, are born with a rhythmic side-to-side eye movement linked to an inherited misrouting of the visual pathways rather than any balance disorder. This form is present from a young age, remains stable over time, and does not indicate underlying ear or brain disease.
Why timing matters
Early observation
Early recognition allows prompt assessment and intervention if needed.
Later presentation
Persistent or worsening signs may indicate progression requiring attention.
The significance of this symptom depends on its context, duration, and associated findings.
Conditions commonly associated
Vestibular Disease
Involuntary rhythmic eye movements occur when the vestibular system sends conflicting signals to the brain.
Otitis Externa in Dogs
Otitis externa can extend into the middle and inner ear structures, where inflammation disrupts the vestibular apparatus responsible for balance and spatial orientation. When the vestibular system is affected, nystagmus may appear alongside head tilt, circling, or loss of coordination.
Hypothyroidism in Dogs
Hypothyroidism may be associated with peripheral vestibular disease in dogs, where reduced thyroid hormone is thought to contribute to nerve or inner ear dysfunction. Nystagmus in this context tends to occur alongside other vestibular signs such as head tilt or ataxia.
Canine Cognitive Dysfunction
Age-related brain changes in cognitive dysfunction can affect the areas of the brain involved in balance and eye movement coordination. Nystagmus in older animals with cognitive decline may reflect broader neurological involvement rather than isolated vestibular disease.
Intervertebral Disc Disease in Dogs
Intervertebral disc disease involving the cervical spine can compress nerve pathways that influence vestibular function or brainstem centres controlling eye movement. Nystagmus in this setting may accompany neck pain, altered gait, or other neurological signs referable to spinal cord compression.
When to explore further
When the symptom is persistent or worsening
When other signs are present alongside
When daily activities or quality of life are affected
When there is uncertainty about the cause
Noting when this symptom occurs, any triggers, and how it changes over time can provide useful information for veterinary discussions.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS