A 32-year-old woman was admitted to our hospital with dizziness lasting 2 weeks. On neurological examination, she showed primary position upbeat nystagmus (Figure 1; video). There were no other neurological abnormalities. T2-weighted magnetic resonance and fluid-attenuated inversion recovery imaging revealed multiple periventricular white matter lesions in the brain. A high-intensity spot was also present in the left side of posterior caudal medulla (Figure 1). We diagnosed her with multiple sclerosis and started 1 mg/d of methylprednisolone pulse therapy for 3 days. She gradually recovered, and the symptom disappeared in 2 weeks. The abnormal lesion in the medulla also became undetectable on magnetic resonance imaging.