Parkinson's disease (PD) is a progressive neurodegenerative condition resulting from the death of the dopamine-containing cells of the substantia nigra. There is no consistently reliable test that can distinguish PD from other conditions that have similar clinical presentations. The diagnosis is primarily clinical, based on a history and examination.
People with PD classically present with the symptoms and signs associated with parkinsonism, namely bradykinesia, rigidity and rest tremor.
Parkinsonism can also be caused by drugs, and conditions that are less common than PD. These include multiple cerebral infarction and degenerative conditions such as progressive supra-nuclear palsy (PSP) and multiple system atrophy (MSA).
Although PD is predominantly a movement disorder, other impairments frequently develop including psychiatric problems such as depression and dementia. Autonomic disturbances and pain (which is rarely a presenting feature of PD) may later ensue, and the condition progresses to cause significant disability and handicap with impaired quality of life for the affected person. Family and carers may also be affected indirectly.
Health and resource implications
PD is a common, chronic, progressive neurological condition, estimated to affect 100–180 people per 100,000 of the population (between 6 and 11 people per 6000 of the general population in the UK) and has an annual incidence of 4–20 per 100,000. There is a rising prevalence with age and a higher prevalence and incidence of PD in males.
The recommendations in this guideline were graded according to the quality of the evidence they were based on. The gradings are available in the NICE guideline and are not shown in this web version.
 The size of the average general practice list in the UK.