Parkinson’s Disease: “On-Off” Phenomenon

The “on-off” phenomenon in Parkinson’s disease (PD) refers to a switch between mobility and immobility in levodopa-treated patients, which occurs as an end-of-dose or “wearing off” worsening of motor function or, much less commonly, as sudden and unpredictable motor fluctuations. Motor complications occur in at least 50% of PD patients who have received levodopa for 5–10 years and constitute a major cause of disability in advanced PD. Motor fluctuations are alterations between periods of improved mobility known as “on” periods during which the patient responds to levodopa and periods of impaired motor function or “off” responses in which the patient responds poorly to levodopa. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.