Ocular flutter induced only by optokinetic stimulation.

Ocular flutter (OF) refers to occasional bursts of involuntary horizontal oscillation around the point of fixation, characterised by rapid horizontal repetitive oscillation without intersaccadic interval in electro-ocular recording. In spite of numerous reports of OF, there has been no previous report describing OF developed by simply looking at moving objects. We report a patient with olivopontocerebellar atrophy (OPCA), with OF induced only by optokinetic stimulation (OKS). A 65-year-old man, with OPCA complained of dizziness and oscillopsia occurring only with a specific type of eye movement. The electro-oculographic recording showed a decreased gain of pursuit, catch-up saccade, and decreased velocity of saccade, and OF was induced only by OKS of more than 40 degrees /second. In OPCA, partial loss of omnipause neurons and/or abnormal firing of burst neurons, especially those involved in optokinetic movement, could be the cause of OF occurring only with OKS.