Ali Rajput, MBBS, FRCPC and Alex Rajput, MD, FRCPC
Division of Neurology, University of Saskatchewan, Saskatoon, SK.
The terms parkinsonism and Parkinson syndrome (PS) are used interchangeably. Two of the three cardinal features--bradykinesia, rigidity and tremor--are necessary to make a diagnosis of PS. Several pathological entities and neuroleptic drugs may produce PS, the most common being Parkinson's disease or idiopathic Parkinson's disease (PD), which is characterized by marked neuronal loss in the substantia nigra and Lewy body (LB) inclusions (Figure 1 is not available online). The prevalence of PS in the Canadian general population is estimated at 300 per 100,000.1 The mean age of onset is 62 years, with both incidence and prevalence rates increasing with age. In a Canadian survey of a community population over age 65 years, 3% had PS.2
Alzheimer disease (AD) is the most common dementing illness in the industrialized countries. Marked cortical neuronal loss, plaques and intraneuronal neurofibrillary tangles are pathological features of AD (Figures 2A and 2B are not available online). More than 5% of the general population over 65 years of age have AD.
Because both PD and AD occur in old age, some individuals will have both. Pathological studies suggest that this overlap is higher than expected in unselected large autopsy series.
