TSPO and Parkinson disease: However, differences in disease severity are unlikely to explain the inconsistency in the findings of previous investigations, in which increased TSPO binding was found in patients examined during the early stage [8, 9] or later stages [7, 10, 12] of PD, and the findings of the more recent studies, in which increases in TSPO binding were not observed in PD patients with various disease durations and severities [13, 14].