Inclusion Criteria:

1. The subject must have undergone a single clinical attack.
2. The subject must have a unifocal clinical presentation.
3. The subject should be enrolled within the period of 90 days after onset of a single unifocal clinical attack (index attack).
4. There must be 2 or more cerebral lesions highly suspicious of MS on the screening MRI, measuring 6mm or more in diameter.
5. Subjects must be between the ages of 18 and 45 years inclusive.
6. Subjects must not have taken corticosteroids (IV, IM and/or PO) within the 30 days prior to the MRI at the baseline visit.
7. Subjects may be male or female. Women of child-bearing potential must practice a medically acceptable method of birth control. Acceptable methods include oral contraceptive, contraceptive patch, long-acting injectable contraceptive, or double-barrier method (condom or IUD with spermicide).
8. The subjects must be willing and able to give written informed consent, prior to entering the study.

Exclusion Criteria:

1. Multifocal clinical presentation.
2. Diseases other than MS responsible for the clinical/MRI presentation. The following laboratory tests must be part of the subject's medical history for differential diagnosis of CIS: ESR, ANA, complement (C3, C4) and anticardiolipin IgG - IgM. In the event that the results of these tests are inconclusive, the following additional tests may be requested by the Eligibility Evaluation Committee: syphilis screening, vitamin B12 and folic acid. In the case of spinal cord CIS presentation, a spinal cord MRI is required for confirmation of diagnosis in the medical history of the subject.
3. Use of experimental or investigational drugs, including IV immunoglobulin, and/or participation in an investigational drug study within 6 months prior to study entry.
4. Use of interferon agents within 6 months prior to the screening visit.
5. Chronic corticosteroid (IV, IM and/or PO) treatment (more than 30 consecutive days) in the 6 months prior to study entry.
6. Pregnancy or breast feeding.
7. Subjects who experience a relapse between the screening (month -1) and baseline (month 0) visits.
8. Life-threatening or other clinically significant disease.
9. A medical or psychiatric condition that affects the subject's ability to give informed consent, or to complete the study, or if the subject is considered by the treating neurologist/physician to be, for any other reason, an unsuitable candidate for this study.
10. A known history of sensitivity to mannitol.
11. A known history of sensitivity to gadolinium.
12. Inability to successfully undergo MRI scanning.