Impact of Ocrelizumab on Cerebrospinal Fluid Biomarkers at Multiple Sclerosis Onset

Inclusion Criteria: Patients must meet the following criteria to be included in this study: * Signed Consent Form * High-risk clinically isolated syndrome or relapsing MS Diagnosis (based on 2017 International Panel Criteria) * Age 18-50 inclusive * Screening within 90 days of first clinical demyelinating event typical of MS with 1 or more inactive lesions typical of MS * No prior MS disease modifying therapy * No corticosteroids within 7 days of first ocrelizumab treatment * EDSS \< 4.0 * A negative urine or serum pregnancy test must be available for premenopausal women and for women \<12 months after the onset of menopause, unless they have undergone surgical sterilization. * Women of childbearing potential must agree to remain abstinent (refrain from heterosexual intercourse) or use one method of contraception with a failure rate of \<1% per year or a barrier method supplemented with spermicide. Contraception must continue for the duration of study treatment and for at least 24 weeks after the last dose of study treatment. A woman is considered to be of childbearing potential if she is postmenarcheal, has not reached a postmenopausal state (≥ 12 continuous months of amenorrhea with no identified cause of other than menopause), and has not undergone surgical sterilization (removal of the ovaries and/or uterus). * Examples of contraceptive methods with a failure rate of \<1% per year include bilateral tube ligation, male sterilization, established hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterine devices. * The reliability of sexual abstinence should be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the patient. Periodic abstinence and withdrawal are not acceptable methods of contraception. * Examples of barrier methods supplemented with the use of spermicide include male or female condom, cap, diaphragm, or sponge. Exclusion Criteria: Patients will be excluded from the study based on the following criteria: * Pregnancy, lactation, or intention to become pregnant during the study * Progressive MS (primary or secondary) * Disease other than MS to explain the first demyelinating event; including AQP4 IgG seropositivity * Unwilling or unsafe to proceed with CSF exams based on coagulopathy or anatomy or other considerations in the judgment of the study investigator * Unwilling or unsafe to proceed with MRI * Active hepatitis B virus infection * Untreated latent or active tuberculosis * Active hepatitis C virus infection * HIV infection * Hypersensitivity to trial medications * History of life-threatening infusion reaction to MAbs