Deep brain stimulation (DBS) is an efficacious neurosurgical treatment for moderate-to-late stage Parkinson's disease (PD). The subthalamic nucleus (STN) and globus pallidus interna (GPi) are two targets extensively studied and used worldwide in treating PD. Although the conventional SYMMETRIC bilateral STN and GPi DBS are shown to be effective in controlling motor symptoms such as bradykinesia, tremor, and dyskinesia, each target has its pros and cons in terms of axial symptom control, medication reduction, cognitive decline, and programming. Therefore, we speculate that an ASYMMETRIC bilateral implantation of DBS leads (i.e., combined unilateral STN and contralateral GPi DBS) may be able to bring the greatest clinical benefits to PD patients by taking advantage of both bilateral STN and GPi DBS at the same time. The preliminary retrospective study containing eight PD patients undergoing asymmetric implantation of DBS demonstrated the safety and efficacy of this treatment strategy during short-term follow-up. This multicenter, single arm, open label study aims to prospectively investigate during the long-term follow-up the safety and efficacy of asymmetric DBS for PD in terms of motor and nonmotor symptoms, medication reduction, cognitive decline, and quality of life.

Inclusion Criteria:

• Diagnosed with idiopathic Parkinson's disease based on the MDS clinical diagnostic criteria for Parkinson's disease
• Aged more than 18 years
• Levodopa challenge test indicating a preoperative levodopa responsiveness over 24% based on MDS UPDRS-III
• the modified Hoehn-Yahr Scale between 2 and 4 under on-medication condition
• Compliance with written informed consent

Exclusion Criteria:

• Atypical parkinsonian syndrome
• History of stroke, encephalitis, neuroleptic uses, MRI scan with evidence of significant brain atrophy, lacunar infracts, or other conditions that might interfere with the intracranial surgery
• Presence of cognitive, or psychiatric or other co-morbidities (e.g., dementia, epilepsy, cranial traumatism, brain tumor, schizophrenia, severe depression or bipolar disorder, personality disorder, etc.) that might interfere with the patient's ability to complete the evaluations or to provide informed consent
• Presence of anatomical abnormalities in the target region
• Clinically significant medical history or that increases pre-/post-operative complications
• Other conditions considered by the investigators that might interfere with the surgery procedure, the follow-ups, and the interpretation of the data