First described by James Parkinson in his classic 1817 monograph, "An Essay on the Shaking Palsy" , Parkinson disease (PD; also known as paralysis agitans) is a progressive neurodegenerative disease that affects between 100 and 200 per 100,000 people over 40, and over 1 million people in North America alone [2,3]. Parkinson disease is uncommon in people younger than 40, and the incidence of the disease increases rapidly over 60 years, with a mean age at diagnosis of 70.5 years .
While PD has traditionally been considered a motor system disorder, it is now recognized to be a complex condition with diverse clinical features that include neuropsychiatric and other nonmotor manifestations in addition to its motor symptomatology . An accurate diagnosis of PD rests on the clinician's ability to recognize its characteristic signs and associated symptoms, especially in the early stages.
This topic will review the clinical manifestations of PD. The diagnosis and treatment of PD are discussed separately. (See "Diagnosis of Parkinson disease" and "Pharmacologic treatment of Parkinson disease" and "Nonpharmacologic management of Parkinson disease" and "Management of comorbid problems associated with Parkinson disease".)
The epidemiology of Parkinson disease is reviewed in detail elsewhere. (See "Etiology and pathogenesis of Parkinson disease", section on 'Epidemiology'.)
The cardinal features of PD are tremor, bradykinesia, and rigidity. A fourth feature, postural instability, is commonly mentioned, although it does not generally occur until much later in the course of the disease and is thus not included in any published diagnostic criteria for PD [6-9]. The severity of motor symptoms appears to be an independent predictor of mortality in patients with PD .