Although deep brain stimulation of the subthalamic nucleus(STN DBS) has become the surgical treatment of choice for Parkinson's disease(PD), a consensus on the timing of surgery is lacking. This study is intended to demonstrate that early, compared with delayed, introduction of STN DBS is more beneficial for PD patients who have developed motor complications.

In this prospective study, 200 PD patients will be recruited for STN DBS over three years, including 133 with motor complications existing for more than three years (late complication group) and 67 less than three years (early complication group). To make a comparison of therapeutic efficacy between the two groups, motor and non-motor symptoms will be assessed using specific rating scales and questionnaires.

Inclusion Criteria:

• Idiopathic Parkinson's Disease with good response to levodopa(i.e. more than 30% improvement in the MDS-UPDRS Part III score after an acute levodopa challenge)
• Presence of fluctuations and/or dyskinesias
• Age ranging from 18 to 75 years old
• Normal brain MRI
• Absence of dementia (Mini Mental State Examination ≥ 26)
• Absence of severe psychiatric diseases
• Written informed consent

Exclusion Criteria:

• Presence of severe metabolic diseases
• Severe cardiac/respiratory/renal/hepatic diseases
• Secondary parkinsonism or multiple system atrophy
• Illiteracy or insufficient language skills to complete the questionnaires
• Poor compliance and unreasonable expectation
• Women who are pregnant or breast feeding
• Simultaneous participation in another clinical trial

The study population are PD Patients with motor complications and an intention of receiving DBS.