Evaluation of Natalizumab for thE Relief of MS Associated FatiGue

TYSABRI® treatment has already demonstrated significant improvement in the quality of life (QoL) of patients with MS. In particular, TYSABRI® add-on treatment to interferon beta-1a has demonstrated improvement in fatigue as measured by the Modified Fatigue Impact Scale (MFIS). Both patients and neurologists report that patients have experienced significant improvements in fatigue shortly after initiating TYSABRI® treatment. Fatigue is both a common and a disabling symptom of MS. Further, there is evidence that fatigue contributes to cognitive difficulties in patients with MS. This study aims to study the effects of TYSABRI® treatment on fatigue and cognition in patients with relapsing forms of MS. The primary objective of this study is to determine the effects of TYSABRI® treatment on fatigue in subjects with relapsing forms of MS as measured by changes in patient-reported Visual Analog Scale for Fatigue (VAS-F). Primary endpoint is the change in the following: 1\. Visual Analog Scale for Fatigue (VAS-F) at three months after initiating treatment with TYSABRI®. Secondary objectives are to measure changes in patient-reported Modified Fatigue Impact Scale (MFIS) and Fatigue Severity Scale (FSS). Secondary endpoints are changes in the following: 1. Modified Fatigue Impact Scale (MFIS) 2. Fatigue Severity Scale (FSS) The tertiary objective of this study is to explore for any effects of TYSABRI® treatment on cognition by assessing changes in the Automated Neuropsychology Assessment Metrics (ANAM). Tertiary endpoints are changes in the Automated Neuropsychology Assessment Metrics (ANAM) consisting of: * Traditional Continuous Performance Test * Running Memory Continuous Performance Test * Simple Response Time * Procedural Response Time * Coding Substitution * Mathematics * Logical Relations * Matching-to-Sample * Stanford Sleepiness Scale