BCHE and Parkinson disease: Several studies show lower cholinesterase activity in PDD than in Parkinson’s disease without dementia (in patients who were not taking cholinesterase inhibitors) (Kuhl et al., 1996; Hilker et al., 2005; Shimada et al., 2009; Klein et al., 2010), particularly in parietal (Kuhl et al., 1996; Hilker et al., 2005; Shimada et al., 2009; Klein et al., 2010) and occipital regions (Kuhl et al., 1996; Klein et al., 2010).