Unidirectional ocular flutter.

Ocular flutter is a rare abnormal eye movement consisting of irregular bursts of to-and-fro bidirectional horizontal saccades and is frequently encountered in association with cerebellar symptoms. We present a patient with a probable post-infectious ocular flutter that exhibited characteristics not previously reported in the literature. Bursts of ocular flutter consisted almost exclusively of initial rightward saccades and were clearly influenced by orbital eye position and the presence of a visual stimulus. The most recent models of saccadic oscillations do not provide an explanation for such atypical features, especially for the systematic directional bias. Based on existing experimental data, we propose that dysfunction of vermal pause neurons in an unstable saccade network could account for such atypical characteristics.