Assessing the Effects of Ongoing Ocrelizumab (OCR) Therapy on Fatigue and Cognition in Veterans With Multiple Sclerosis

Inclusion Criteria: * Age 18-75, men and women. * Confirmed diagnosis of Multiple Sclerosis (MS) (relapsing or progressive forms). * Expanded Disability Status Scale score between 0 and 7.5. * On continuous ocrelizumab therapy for at least 1 year. * Women of childbearing potential: Must agree to remain abstinent or use acceptable contraceptive methods during the study and for 6 months after the. last ocrelizumab dose; must have a negative pregnancy test before enrollment. Exclusion Criteria: * Patients without a confirmed diagnosis of MS based on McDonald 2017 Criteria. * Not on ocrelizumab therapy for at least 6 months prior to study start. * Currently receiving other disease-modifying therapies for MS in addition to Ocrelizumab. * Experienced an MS relapse or corticosteroid use within the last 30 months prior to enrollment. * History of major psychiatric conditions (severe depression, schizophrenia, bipolar disorder) interfering with assessments. * Significant cognitive impairment due to non-MS-related conditions (Traumatic brain injury, dementia, other neurodegenerative diseases). * Other major neurological disorders (e.g., Parkinson's, epilepsy, stroke). * History of alcohol or substance abuse within the past year. * Uncontrolled comorbidities (severe cardiovascular disease, diabetes with complications, renal/liver failure). * Uncorrected vision or hearing impairments interfering with cognitive testing. * Unable to provide informed consent due to cognitive or legal reasons. * Pregnant, lactating, or planning to become pregnant during the study period. * Currently enrolled in other interventional clinical trials affecting cognitive or fatigue outcomes. * Known presence of recurrent or chronic infections (Human Immunodeficiency Virus, syphilis, tuberculosis). * History or presence of infectious causes of myelopathy (e.g., syphilis, Lyme disease, Human T-lymphotropic virus type 1). * Active bacterial, viral, fungal, mycobacterial infection requiring recent hospitalization or IV antibiotics. * History of cancer (except treated basal cell, in situ squamous cell, or resolved cervical carcinoma). * History of or currently active primary or secondary immunodeficiency. * Severe allergic or anaphylactic reactions to monoclonal antibodies. * Systemic autoimmune disorders causing progressive neurological disease (e.g., lupus, Sjögren's). * Concomitant diseases requiring chronic systemic corticosteroid or immunosuppressant use. * Significant uncontrolled cardiovascular, pulmonary, renal, hepatic, endocrine, or gastrointestinal disease. * History of other neurologic disorders (e.g., progressive multifocal leukoencephalopathy, central nervous system/spinal tumors, hereditary spastic paraparesis, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome, neuromyelitis optica-spectrum disorder). * Recent systemic corticosteroid therapy within 4 weeks prior to baseline. * Prior MS treatments with cyclophosphamide, mitoxantrone, or bone marrow transplant. * Receipt of live, attenuated, or inactivated/component vaccine within 6 weeks before enrollment. * Laboratory abnormalities: Positive hepatitis B markers, elevated liver enzymes (AST/ALT ≥2x ULN), cytopenias, low IgG/IgM.