Visual illusions in a patient with lateral medullary syndrome. The disturbance of visual perception associated with nystagmus is a rare phenomenon. This is a case of a 61-year-old woman who developed progressive right hemisensory deficit, left facial sensory deficit, vertigo, staggering to the left, left ptosis, vertical diplopia, and ataxia of the left upper extremity. She had rotatory nystagmus in primary position, which increased in amplitude with left gaze. The above signs and symptoms were consistent with lateral medullary syndrome. During her rehabilitation, the patient complained of visual disturbances typical of oscillopsia. These disturbances, or illusions, are compensatory mechanisms for nystagmus and its resultant retinal error. The purpose of this case presentation was to study the pathophysiology underlying oscillopsia in patients with nystagmus and to stimulate awareness of such visual disturbances in stroke patients. 