We used conventional MRI and hyperpolarized 13C magnetic resonance spectroscopy (HP 13C MRSI) quantitative imaging of pyruvate and urea to assess lesion pathology and the metabolic signature in a model of multiple sclerosis (MS). T2 sequences detected white matter lesions and gadolinium-enhanced MRI showed blood-brain-barrier breakdown. HP 13C MRSI revealed increased lactate production and lactate-to-pyruvate ratios while urea levels remained unchanged. This is consistent with macrophage/monocyte infiltration into the CNS found in the model. Altogether, these findings demonstrate that HP 13C MRSI has potential to monitor macrophage infiltration and innate immune activation in inflammatory diseases of the central nervous system.