This is a clinical finding on examination. The corresponding symptom is oscillopsia, although it is often absent. Nystagmus is common in disorders that cause vertigo or ataxia.

Investigations to consider:

Down beat, MRI: cervicomedullary lesions, Chiari Malformation, Multiple sclerosis, brainstem tumor, brainstem stroke, spinocerebellar degeneration
Convergence-Retraction: MRI: dorsal midbrain lesions
Ocular bobbing, MRI: pontine lesions, hydrocephalus,
Periodic alternating nystagmus PAN: anti-GAD antibodies

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