Striatal and extrastriatal dysfunction in Parkinson’s disease with dementia: a 6‐[18F]fluoro‐l‐dopa PET study

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Abstract
We investigated the relative differences in dopaminergic function through the whole brain in patients with Parkinson’s disease without dementia (PD) and with dementia (PDD) using 6‐[18F]fluoro‐l‐dopa (18F‐dopa) PET and a voxel‐by‐voxel analysis. The 10 PD and 10 PDD patients were equivalently disabled, having mean scores of 3.2 ± 0.6 and 3.2 ± 0.7, respectively, on the Hoehn and Yahr rating scale. 18F‐dopa influx constant (Ki) images of those patients and 15 normal age‐matched subjects were transformed into standard stereotactic space. The significant differences between the groups (expressed in mean regional Ki values) were localized with statistical parametric mapping (SPM) on a voxel‐by‐voxel basis. Compared with the normal group, SPM localized declines of the 18F‐dopa Ki bilaterally in the putamen, the right caudate nucleus and the left ventral midbrain for the PD group (P < 0.01, corrected). Com pared with the normal group, the PDD group showed reduced 18F‐dopa Ki bilaterally in the striatum, midbrain and anterior cingulate area (P < 0.01, corrected). A relative difference in 18F‐dopa uptake between PD and PDD was the bilateral decline in the anterior cingulate area and ventral striatum and in the right caudate nucleus in the PDD group (P < 0.001, corrected). Accordingly, we conclude that dementia in PD is associated with impaired mesolimbic and caudate dopaminergic function.