Oxidative stress has been linked to neuroinflammation that leads to demyelination in multiple sclerosis (MS). While most studies focus on older MS patients, the underlying cause of oxidative stress at this stage of the disease may be obscured. In this study, cerebral metabolic rates of oxygen and glucose in young adult relapsing-remitting MS patients were measured with simultaneous PET/MRI. Several brain regions, most associated with the corticostriatal pathway, exhibited increased oxygen metabolism and decreased glucose metabolism in young MS patients when compared to healthy controls. These observations may elucidate the mechanism for mitochondrial dysfunction and neuroinflammation in MS pathophysiology.