Janis Miyasaki, MD, FRCPC
Mount Sinai Hospital,
Each year Parkinson's disease (PD) affects 4.5-21 people out of every 100,000. The prevalence rate is 200/100,000 members of the population. As the population ages, the prevalence can be expected to increase since the risk of developing PD steadily increases with each decade of life.1 The cardinal symptoms of PD are tremor, rigidity, akinesia and postural instability.2 A patient is diagnosed with Parkinson's disease based on him/her having a history consistent with PD, and showing the clinical signs on examination. Therefore, the physician must be familiar with the classic appearance of each sign of PD and with the alternative diagnoses that are implied by any variance in symptoms.
The tremor in PD is classically 3-5 Hz and is described as pill-rolling, due to the rhythmic opposition of the index finger and thumb. Tremor is seen at rest, however, in some cases it may only be seen if the patient is distracted by the use of manoeuvres such as mental arithmetic. While the patient is walking, the affected arm will often shake. Anxiety markedly increases the tremor, whereas it abates during sleep. Tremor may also be seen with postural maintenance or during a physical action. If the postural or kinetic component of the tremor is predominant, the physician should consider an enhanced physiologic tremor or essential tremor as the diagnosis.