Comparison of Campath and Rebif Treatment on Cognition in Multiple Sclerosis (MS)

The current will use a neuropsychological evaluation capable of detecting the broad range of cognitive difficulties associated with relapsing remitting MS (RRMS). It is a sub-study of an investigation already underway, called Care-MS II, in which participants diagnosed with RRMS are treated with either Campath® or Rebif®. We will observe those participants already assigned to one of the two study arms in Care-MS II and compare cognitive functioning over time of those taking Campath® and those taking Rebif®. We will also compare the change in cognitive functioning for each active group to that of a matched control group. This will help to control for practice effects and help to establish whether either medication helps to truly stabilize cognitive decline (i.e., relative to non-MS controls). We will obtain neurocognitive data at baseline (prior to the first study dose of Campath® or Rebif®), 12 months (before second dose for Campath® participants), 14 months (2 months after the second dose for Campath® participants), 24 months (prior to the third dose for Campath® participants), and 26 months (2 months after the third dose for Campath® participants). The neurocognitive battery will include gold-standard traditional neuropsychology measures as well as newer, validated computerized measures capable of detecting changes in attention and processing speed that are often missed by traditional measures. Since participants in Care-MS II will also have MRI data at baseline, 1 year, and 2 years, cognitive findings will be correlated with MRI data and analyzed in a post-hoc, exploratory manner for the participants with MS. Hypotheses include: * 1: Participants taking Campath® will demonstrate relative stability in cognitive functioning relative to those taking Rebif®. Specifically, the cognitive performance of Rebif® participants will decline somewhat over time, but the cognitive performance of Campath® participants will remain stable. * 2: Participants taking Campath® will demonstrate similar cognitive change (i.e., change in scores over 2 years) as normal, matched controls. * 3: Participants taking Rebif® will demonstrate greater cognitive change (i.e., change in scores over 2 years) as compared to normal, matched controls. * 4: Cognitive stability in Campath® participants will correlate with stability in MRI parameters. * 5: Cognitive change in Rebif® participants will correlate with greater activity on MRI parameters.