Dissociated Elliptical Pendular Nystagmus in MS

This is a patient with multiple sclerosis who presented with oscillopsia. Seen in the video is an elliptical pendular nystagmus in both eyes that was dissociated. Here, the term "dissociated" refers to the fact that the nystagmus is (slightly) more intense in the left eye as compared to the right eye. This can be seen on examination, and the patient also experienced more oscillopsia in the left eye as compared to the right eye when each eye was covered individually. When pendular nystagmus is seen, it is usually in the setting of MS or oculopalatal tremor (OPT). Pendular nystagmus due to MS is often dissociated, and the eye with more intense nystagmus is often the eye with poorer visual function due to optic nerve disease. Pendular nystagmus due to OPT may be disjunctive, meaning that the trajectory or the vector of nystagmus can be different in each eye. She also had a mild right internuclear ophthalmoparesis in the right eye that was best seen as an adduction lag OD when having her make horizontal saccades to the left.