Parkinson disease: managing a complex, progressive disease at all stages.

Parkinson disease is a complex neurodegenerative disease with both motor and nonmotor symptoms. Levodopa remains the mainstay of therapy but is associated with motor complications as the disease progresses. A levodopa-sparing strategy may reduce or delay the onset of motor complications. New medical and surgical therapies offer improved control of motor complications in advancing disease. Recognition and treatment of nonmotor symptoms can improve quality of life throughout the course of the disease.