Antibodies, Monoclonal, Humanized/therapeutic use; Brain/drug effects; Immunologic Factors/therapeutic use; Interferon-beta/therapeutic use; Magnetic Resonance Imaging; Multiple Sclerosis, Chronic Progressive/drug therapy; Multiple Sclerosis, Relapsing-Remitting/drug therapy; Adult; Antibodies, Monoclonal, Humanized/administration & dosage; Antibodies, Monoclonal, Humanized/adverse effects; Brain/pathology; Drug Therapy, Combination; Female; Glucocorticoids/administration & dosage; Humans; Immunologic Factors/administration & dosage; Immunologic Factors/adverse effects; Infusions, Intravenous; Interferon beta-1a; Interferon-beta/administration & dosage; Interferon-beta/adverse effects; Male; Methylprednisolone/administration & dosage; Middle Aged; Multiple Sclerosis, Chronic Progressive/pathology; Multiple Sclerosis, Relapsing-Remitting/pathology; Natalizumab; New York; Predictive Value of Tests; Prospective Studies; Pulse Therapy, Drug; Single-Blind Method; Time Factors; Treatment Outcome