Most importantly, co-existing Alzheimer pathology with extracellular β-amyloid in cortical and subcortical regions and tau pathology in hippocampal and neocortical regions is common in those with cognitive impairment.123 These patients have also a higher risk of amyloid angiopathy and a more rapid decline than PDD patients without Alzheimer’s disease pathology.124 Furthermore, alpha-synuclein deposition in the limbic and neocortical regions (frontal and temporal) are also common in PD patients with cognitive decline. Here, SNCA is linked to Mental deterioration.