The primary aim of this study is to observe any changes in MRI in MS patients who have switched from 20mg injections/day to 3 40mg injections/week of glatiramer acetate.

The primary aim of this study is to observe the effect of switching from daily injections of 20mg glatiramer acetate (GA) (20mg/daily) to GA 40mg three times a week (40mg x 3/weekly) on thalamus pathology, as measured by changes in diffusion-tensor imaging (DTI) in patients with relapsing-remitting multiple sclerosis (RRMS). We hypothesize that GA 40mg x 3/weekly will exert similar, if not better effect on prevention of thalamic pathology, as compared to GA 20mg/daily. The secondary objective of this study is to investigate the effect of switching from GA 20mg/daily to GA 40mg x 3/weekly on evolution of microstructural changes in normal appearing white matter (NAWM) and normal appearing gray matter (NAGM), as measured by DTI.

Inclusion Criteria:

• MS patients diagnosed with MS according to the McDonald criteria
• MS patients having a relapsing disease course
• Being on GA monotherapy (20mg/daily sc) for at least 12 months prior to the standard of care MRI at the time of switch to GA 40mg x 3/weekly
• Having standard of care 3T MRI scan while on GA 20mg/daily treatment for at least 12-18 months prior to the start day of the of the GA 40mg x 3/weekly and at the time of switch to GA 40mg x 3/weekly Age over 18
• Pass MRI health screening (in case of EGFR <59, the contrast will not be applied)
• None of the exclusion criteria

Exclusion Criteria:

• Patients who had a relapse within 30 days prior to MRI scan date
• Patients who received steroid treatment within 30 days prior to the MRI scan date
• Women who are pregnant, lactating or of childbearing age who do not consent to approved contraceptive use during the study
• MS patients who used other imunomodulatory or immunosuppressant treatment other than GA during the 12 months prior to start of GA 40mg 3/weekly (e.g., IFN-β, mitoxantrone, cyclophosphamide, cladribine, fludarabine, cyclosporine, total body, azathioprine, methotrexate, IVIG, cellcept, natalizumab, etc.)

One hundred fifty (150) consecutive RRMS patients who are on treatment with GA 20mg/daily for at least 12 months and who switched to GA 40mg x 3/weekly, because of convenience of application, will be recruited in the study.