The purpose and main objective of this study is the research of pre-operative and operative predictive factors of short-term (1-year) and long-term (15-years) improvement of quality of life, motor and non-motor symptoms in Parkinson's disease patients who have undergone to bilateral Subthalamic Nucleus Deep Brain Stimulation.

The hypothesis of the study is that the definition of pre-operative and operative predictive factors could be able to improve the pre-operative prognostic accuracy of outcome and complications after surgery, allowing also a better selection of the most suitable candidates for bilateral Subthalamic Nucleus Deep Brain Stimulation.

For example, we can suppose that an older age at surgery, elevated axial score, a less preoperative dopa-responsiveness, the presence of mild executive dysfunction at surgery or an unfavourable social status, could negatively influence the short and long term surgery outcome

Subthalamic NucleusDeep Brain Stimulation (STN-DBS) represents a short and long-term effective treatment in Parkinson's disease (PD) patients. Various randomized controlled trials have confirmed the superiority of STN-DBS compared to the best medical treatment in patients with advanced Parkinson disease in term of improvement of motor function and quality of life. On the other hand, STN- DBS is associated with an increased risk of adverse events compared to best medical treatment.

Data from previous meta-analysis have shown that only pre-operative dopa-responsiveness can predict the clinical efficacy and outcome of STN-DBS. In particular the improvement of STN-DBS on quality of life mainly concern the physical aspects of functioning with a lower improvement on social and cognitive aspects.

However, not all of PD symptoms respond similarly to STN-DBS. In particular the effects of STN-DBS on the so-called levodopa unresponsive symptoms (i.e. gait and balance symptoms, autonomic dysfunction, sleep disorders, cognitive decline and speech and swallowing troubles) are modest or absent. Furthermore, levodopa unresponsive symptoms are one of the main causes of impairment and disability in advanced PD patients. Bearing in mind these informations, the clinical phenotyping of candidates for surgery appear crucial for the prediction of DBS outcome and selection of better candidates. In the recent years, several papers highlighted and expanded the list of possible predictive factors, from a motor point of view to non-motor symptoms and psychosocial aspects.

In this setting, the aim of our study is to determine the pre-operative and operative short-term (1-year) and long-term (15-years) predictive factors of improvement of quality of life and motor and non-motor symptoms in a large cohort of PD patients who have undergone to bilateral STN-DBS. The better definition of short-term and long-term predictive factors and its association with the different PD different clinical phenotypes could allow in the future a better definition of the effects of STN-DBS on quality of life and motor and non-motor symptoms in the different PD clinical phenotypes.

In the same way, it could be assumed that a better definition of pre-operative predictive factors of surgical, hardware and stimulation-induced STN-DBS side effects in the short term, could also allow a better definition of the risk-to-benefit ratio and outcome after STN-DBS surgery

Inclusion Criteria:

• Patients with Parkinson's disease treated with bilateral Subthalamic Nucleus Deep Brain Stimulation

Exclusion Criteria:

• Patients treated with bilateral Subthalamic Nucleus Deep Brain Stimulation not affected by Parkinson's Disease
• Patients with Parkinson's disease treated with unilateral Subthalamic Nucleus Deep Brain Stimulation

Patient with Parkinson's disease treated with bilateral Subthalamic Nucleus Deep Brain Stimulation