The purpose of the study is to evaluate the safety, tolerability and activity of Fampridine-SR when administered for up to 36 additional months in patients who previously participated in the MS-F204 study or until it becomes commercially available, whichever comes first.

Multiple sclerosis (MS) is a disorder of the body's immune system that affects the central nervous system (CNS). Normally, nerve fibers carry electrical impulses through the spinal cord, providing communication between the brain and the arms and legs. In people with MS, the fatty sheath that surrounds and insulates the nerve fibers (called "myelin") deteriorates, causing nerve impulses to be slowed or stopped. As a result, patients with MS may experience periods of muscle weakness and other symptoms such as numbness, loss of vision, loss of coordination, paralysis, spasticity, mental and physical fatigue and a decrease in the ability to think and/or remember. These periods of illness may come (exacerbations) and go (remissions). Fampridine-SR is an experimental drug that has been reported to possibly improve muscle strength and walking ability for some people with MS. This study will evaluate the effects and possible risks of taking Fampridine-SR in MS patients over a long period of time.

Inclusion Criteria:

• Patient must have been previously enrolled in the Acorda Therapeutics MS-F204 study and received either Fampridine-SR or placebo
• Patient with clinically defined multiple sclerosis (the diagnostic criteria based on: McDonald WI, et al. Recommended Diagnostic Criteria for Multiple Sclerosis: Guidelines from the International Panel on the Diagnosis of Multiple Sclerosis. Annals of Neurology. 2001; 50: 121-127)
• Patient must be at least 18 years of age. Any patient who is now over the age of 70 must be in good overall health in the judgment of the investigator
• Patient must be of adequate cognitive function, as judged by the Investigator
• Patients who are women of childbearing potential must have a negative urine pregnancy test at the screening visit

Exclusion Criteria:

• Female patients who are either pregnant or breastfeeding.
• Women of childbearing potential who are not using a specified birth control method
• Patients discontinued prematurely from the MS-F204 study
• Patients with a history of seizures or with evidence of past, or possible epileptiform activity on an EEG
• Patient with either a clinically significant abnormal ECG or laboratory values at the MS-F204 EXT screening visit
• Patient with severe renal impairment
• Patient with angina, uncontrolled hypertension, clinically significant cardiac arrhythmias, or any other clinically significant cardiovascular abnormality, as judged by the Investigator
• Patient with a known allergy to pyridine-containing substances or any of the inactive ingredients of the Fampridine-SR tablet
• Patient who has received an investigational drug (other than Fampridine-SR or placebo under MS-F204 study) within 30 days of the MS-F204EXT screening visit or a patient who is scheduled to enroll in an investigational drug trial at any time during this study
• Patient who has a history of drug or alcohol abuse within the past year