Motivation: There remains an absence of imaging modalities capable of probing the neuroinflammatory processes that precede the well-defined brain structural changes in Primary Progressive Multiple Sclerosis (PPMS). Goal(s): We investigated whether hyperpolarized [1-13C]pyruvate MRI can delineate alterations in cerebral glycolytic and oxidative metabolism between treatment naïve PPMS and healthy volunteers. Approach: Two treatment naïve PPMS patients and two sex matched healthy volunteers underwent [1-13C]pyruvate MRI to characterise cerebral glycolytic and oxidative metabolism. Results: A global increase in [1-13C]lactate: [1-13C]pyruvate was found in both PPMS patients relative to sex-matched healthy controls (0.23 ± 0.12 vs 0.16 ± 0.08). The 13C bicarbonate:[1-13C]pyruvate ratio was no different. Impact: These preliminary findings demonstrate a global increase in cerebral glycolytic metabolism in treatment naïve PPMS relative to age and gender matched healthy controls. This may reflect diffuse neuroinflammatory processes and suggests [1-13C]pyruvate MRI could be used to monitor disease activity.