Pridopidine (ACR16) belongs to a novel class of central nervous system compounds in development for the treatment of Huntington disease. The objective of the study was to investigate the metabolic changes in patients with Huntington disease before and after pridopidine treatment. METHODS: [(18)F]Fluorodeoxyglucose positron emission tomographic imaging was used to measure the regional cerebral metabolic rate of glucose at baseline and after 14 days of open-label pridopidine treatment in 8 patients with Huntington disease.