Description

• A progressive neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra and other dopaminergic regions of the brain.
• Cardinal symptoms include resting tremor, rigidity, bradykinesia, and postural instability.

Epidemiology

Incidence

• 21 per 100,000 person-years
• Average age of onset: ~60 years
• Slightly more common in men than women

Prevalence

• Second most common neurodegenerative disease after Alzheimer disease
• 1 to 2/1,000 persons
• 0.3% of general population and 1–2% of those ≥60 years of age and up to 4% of those ≥80 years of age
• Affects 1 million people in the United States and 5 million worldwide

Etiology and Pathophysiology

Dopamine depletion in the substantia nigra and the nigrostriatal pathways results in the major motor complications of PD.

• Pathologic hallmark: selective loss of dopamine-containing neurons in the pars compacta of the substantia nigra
• Loss of neurons accompanied by presence of Lewy bodies (hyaline inclusion bodies) and Lewy neuritis

Genetics
Mutations in multiple autosomal dominant and autosomal recessive genes are linked to PD/parkinsonian syndrome particularly when the age at symptom onset is <50 years.

Risk Factors

• Age and family history of PD or tremor.
• Lifelong pesticide use by farmers, especially of rotenone and other carbamate, is associated with risk of developing PD.
• Repeated head trauma and living in rural areas, drinking well water, working in a wood pulp mill

General Prevention

Physical activity that has been linked to decreased risk of development of PD include weight training, running, dancing, yoga, and traditional Chinese martial arts (1).

Commonly Associated Conditions

Cognitive abnormalities, autonomic dysfunction (e.g., constipation, urinary urgency), sleep disturbances, mental status changes (depression, psychosis, hallucinations, dementia), orthostatic hypotension, and pain