Extrastriatal spreading of microglial activation in Parkinson's disease: a positron emission tomography study

The neuroinflammatory glial response contributes to the degenerative process in Parkinson's disease (PD). However, the pattern of microglial progression remains unclear. We evaluated microglial activation in early stage PD patients by quantifying changes in neuroinflammation using PET with [C-11]DPA713, a selective PET tracer for microglial activation. Eleven PD patients (Hoehn and Yahr stages 1-2) without dementia underwent the [C-11]DPA713 PET scan two times with 1 year apart. The binding potential (BPND) was estimated with the simplified reference tissue model. Voxelwise and regions of interest analyses were used to compare the regional BPND among groups. Significant increase in [C-11]DPA713 BPND was found extrastriatally in the occipital, temporal and parietal cortex in PD patients, and the degree of BPND became much higher over the brain regions predominantly in the temporal and occipital cortex 1 year later. The current results indicated that an extrastriatal spreading of microglial activation reflects one of PD pathophysiology occurring at an early stage.