A 37-year-old female with multiple sclerosis had initial presentation 5 years ago with optic neuritis that completely resolved without treatment. 3 years ago she had sensory and motor involvement of the upper extremities and was treated with corticosteroids. 2 years ago she was treated with interferon beta-1A. 3 days ago she developed decreased sensation of the left lower trunk without tingling, pain, gait problems, bowel or bladder problems, or systemic symptoms. Exam shows normal visual fields with a right afferent pupillary defect. There is decreased sensation to light touch over the right trunk. Rapid alternating movements, finger tapping, heal tapping to shin, and finger to nose are all-normal. Select the appropriate treatment.
3. Interferon beta-1B