Do non-motor symptoms in Parkinson's disease differ from essential tremor before initial diagnosis? A clinical and scintigraphic study.

Background: Non-motor symptoms (NMS) in Parkinson's disease (PD) are common, increase the patients' disability and have a significantly negative impact on their quality of life. Essential tremor (ET) is also affected by non-motor symptoms and often enters into the differential diagnosis with PD. Brain scintigraphy with [(123)I]β-CIT SPECT is a technique used to facilitate differential diagnosis between PD and ET.