Muscle Function, Muscle Disease, and Positron Emission Tomography-Computed Tomography: A Narrative Review.

18F-fluorodeoxyglucose (18F-FDG) is a radiopharmaceutical that exhibits glucose-like kinetics and is used in positron emission tomography (PET). 18F-FDG is used for cancer diagnosis in clinical practice. However, 18F-FDG uptake is also observed in normal organs, such as the brain, liver, and heart, with high glucose consumption. Moreover, 18F-FDG uptake is also observed in muscles, where its accumulation and radioactivity reflect muscle activity. Dystonia is characterized by excessive muscle movement. Recently, 18F-FDG and technetium-99m-methoxyisobutyl isocyanide ([99mTc]MIBI) have been used for the diagnosis and botulinum toxin therapy evaluation of dystonia. This review aimed to summarize the utility of 18F-FDG-PET for the evaluation of muscle activity and diagnosis of muscle diseases such as dystonia, polymyositis, dermatomyositis, and polymyalgia rheumatica.