Jerk Nystagmus (Periodic Alternating Nystagmus)

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"This young man, with probable Multiple Sclerosis, has a regular form of periodic alternating nystagmus. In center gaze, a null period without nystagmus lasts about 30 seconds. We are now beginning to see a right beating nystagmus. The amplitude of the nystagmus gradually builds up and decreases over a period of about 90 seconds. During the right beating nystagmus, the patient experiences a horizontal oscillopsia. There is a small torsional component to the nystagmus. While the nystagmus is beating to the right, if the subject turns his face toward the right and places his eyes in left gaze a null position can usually can be found in which the oscillopsia and the nystagmus decreases. The amplitude of the right beating nystagmus is decreasing, and there will be another null period in center gaze in which the nystagmus is not present. Oscillopsia is absent during the null period. A left beating nystagmus will then begin to build in amplitude. It will also gradually increase in size and then gradually decrease in amplitude over a period of another 90 seconds. While the nystagmus is beating toward the left, if the patient turns his face toward the left and places the eyes in right gaze, another null zone of decreased nystagmus and decreased oscillopsia is present."
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