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.
Saito T, Aizawa H, Sawada J, Katayama T, Hasebe N. Lesion of the Nucleus Intercalatus in Primary Position Upbeat Nystagmus. Arch Neurol. 2010;67(11):1403-1404. doi:10.1001/archneurol.2010.285