Asymmetric glucose uptake in leg muscles of patients with Multiple Sclerosis during walking detected by [18F]-FDG PET/CT

BACKGROUND: In patients with Multiple Sclerosis (MS), comparative leg muscle strength asymmetries are common and typically accompanied by walking difficulties. Underlying mechanisms for these asymmetries are not completely known, but altered muscle energetics may play a role. OBJECTIVE: To investigate glucose uptake asymmetries in leg muscles of patients with mild MS during walking. METHODS: Eight MS and 8 healthy control (CON) participants performed a 15-min treadmill walking test at self-selected speed. They were injected with a glucose tracer (F-18-FDG) two minutes into the test and immediately upon completion, underwent Positron Emission Tomography/Computed Tomography (PET/CT) imaging. RESULTS: MS group walked at a lower speed than the healthy control group (P < 0.01), however it was found that: 1) ([F-18]-FDG) uptake in knee and hip flexors was higher compared to the CON group (P = 0.02); 2) the MS group exhibited asymmetrical strength of the knee flexors (P = 0.03); 3) [F-18]-FDG uptake was significantly lower in the weaker knee flexors of patients with MS (P < 0.01). CONCLUSIONS: [F-18]-FDG uptake and strength asymmetries in the legs of patients with MS indicate greater metabolic costs during activity, which may play a major role in premature muscle fatigability and subsequent impaired walking capacity.