The study will enroll 15 subjects from the Cleveland Clinic Mellen Center patient population. Participants must have been on Gilenya for at least 6 months at the time of study entry. The study will involve three assessments: at baseline, six months, and one year. At each time point, participants will undergo 7T MRI of the brain with and without contrast. Participants will also undergo a battery of neurometric testing at each time point. The tests will include the Brief Visuospatial Memory Test - Revised (visuospatial skills), the iPadTM Processing Speed Test (processing speed), the Selective Reminding Test (verbal learning and memory), and the Delis-Kaplan Executive Function System Sorting Test (problem-solving skills; can only be administered at baseline and one year due to version limitations).