TSPO and central nervous system disorder: In normal conditions, TSPO expression is low throughout the brain.1,2 In diseases of the central nervous system (CNS), high levels of TSPO have been observed in infiltrating blood-borne cells and in activated microglia.3 TSPO expression increases after neuronal damage from inflammatory, ischemic, degenerative, and neoplastic diseases.4 Microglia are activated not only in the surroundings of focal lesions but also in the distant, anterograde, and retrograde projection areas of the lesioned neural pathway.5