Istradefylline Effect Protocol on Parkinson's Disease Tremor

This is an investigator-initiated trial. In this 6-month open label, single arm, exploratory pilot study, the investigator intends to enroll a pilot sample of 25 patients with Parkinson's disease who are being started on the novel FDA approved medication "Istradefylline'' as an add on therapy for management of their motor symptoms (based on the judgment of the movement disorders specialist, if patients are in sub-optimal management of their symptoms on maximum tolerable dose of their dopaminergic medications). The investigator will evaluate their motor symptoms before starting the new medication, including their MDS-UPDRS total and MDS-UPDRS-III scores.