Pathophysiology, Patient Burden, and Recognition of OFF Episodes of Parkinson Disease.

​​​​ The pathophysiology of PD has been elusive, but the motor symptoms of the disease are believed to result from a dopamine deficiency in the substantia nigra. As a patient's disease progresses, OFF episodes emerge due to a shorter duration of response to levodopa treatment. OFF episodes include both motor and nonmotor symptoms, are common, and can occur at any time. OFF episodes can be predictable or unpredictable, significantly impact patient quality of life and functionality, and place a burden on families. By facilitating communication with patients and care partners using assessment tools, clinicians can detect symptoms of OFF episodes earlier.