Idiopathic Downbeat Nystagmus, Decreasing with Convergence

This is a 25-yo-woman who experienced vertically oscillopsia for 1 year, and was found to have downbeat nystagmus. Interestingly, there were no other cerebellar ocular motor signs - e.g., normal saccades, smooth pursuit, VOR suppression, and no gaze-evoked nystagmus, although her (pure) downbeat was more prominent in right and left gaze. There was no appendicular ataxia and neurologic examination was otherwise normal. With convergence, her downbeat actually decreased (will usually increase with most downbeat nystagmus/cerebellar syndromes), and base out prism improved her oscillopsia mildly. Neuroimaging and work-up for paraneoplastic, toxic/metabolic, autoimmune/rheumatologic syndromes in addition to common spinocerebellar ataxias was unrevealing. Her examination was completely unchanged at 3 years. Number of Figures and legend for each: 0 Number of Videos and legend for each: 1, Patient with downbeat nystagmus, improved with convergence