A 67-year-old woman presented with open-ring enhancement on MR images in the thoracic spinal cord. Steroid therapy improved the patient's paraplegia, but six months later she developed left hemiparesis and a new open-ring enhancement appeared in the right cerebrum. Despite high-dose methylprednisolone therapy and plasmapheresis, another lesion appeared at the middle portion of the left centrum semiovale. Stereotaxic brain biopsy demonstrated active demyelination characteristics of multiple sclerosis (MS). This case indicates that openring enhancement can help differentiate MS from nondemyelinating disease, and that MS showing ring enhancement may contribute to disease severity and need more intensive immunomodulatory therapies.