The diagnosis of parkinsonism depends on recognizing its component clinical features. Parkinsonism includes Parkinson's disease (PD) and all the varied conditions with clinical features resembling those of PD. To identify patients with parkinsonism correctly it is important to be able to recognize the cardinal clinical features of PD, namely akinesia, lead-pipe rigidity, rest tremor, and postural instability. The next critically important step is to determine whether they suggest PD or one of the other non-PD causes of parkinsonism (see Table 2.1). This latter distinction will enable effective treatment strategies to be devised and a meaningful discussion of prognosis and genetic implications to be undertaken. The entire process of identifying parkinsonism and assigning a specific clinical diagnosis is particularly challenging in the elderly because many of the motor changes associated with normal ageing resemble parkinsonism. Additionally, several medical conditions that are common in this age group can result in parkinsonism that may incorrectly be considered evidence of PD.

The clinical signs of PD

Of the cardinal motor signs of PD, akinesia is perhaps the most disabling. Slowness, difficulty in initiation, and a reduction in the amount or amplitude of voluntary movement (Rodnitzky and Uc 1997) characterize akinesia (see Table 2.2). A great variety of clinically recognizable signs result from akinesia. A lack of facial expression attended by reduced blink rate is one of the most apparent manifestations of akinesia. Additional findings are diminished arm swing on one or both sides of the body, difficulty arising from a chair, a slow, short stepped gait, en bloc turning, and soft, poorly articulated speech (hypophonia).