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An 83-year-old man visited the ED with sudden-onset diplopia. There were no diurnal changes in symptoms and he had no headaches. On neurological examination, pupils were isocoric and right conjugate gaze was impossible in both eyes. The right eye was completely unable to gaze leftward, whereas the left eye was able to gaze leftward with gaze-directional nystagmus. Vertical gaze was intact in both eyes ( figure 1, online supplemental video 1).