"Saccadic nystagmus" in cerebellar cortical atrophy.

An ocular dyskinesia designated "saccadic nystagmus" was observed in a patient with cerebellar cortical atrophy. Saccadic nystagmus is a sustained ocular dyskinesia present during visual fixation and abolished by eye closure. It is difficult to distinguish visually from either pendular or jerk nystagmus without eye movement recordings. The oscillations are horizontal and rapid and may be influenced by direction of gaze. Caloric nystagmus (eye closed) and optokinetic nystagmus were normal in our patient. Visual fixation abolished caloric nystagmus, which was replaced by saccadic nystagmus.