Parkinson's disease (PD) is a progressive disease, characterized by dopaminergic neurons degeneration in the substantia nigra. Postural and gait disorders usually occur in advanced PD patients. However, existing drugs and deep brain stimulation (DBS) therapy are not effective enough for these axial symptoms or cannot maintain long-term efficacy, which seriously reduce patients' quality of life. Sacral nerve stimulation(SNS) is a treatment for urinary symptoms in PD. It has been reported that SNS can also improve PD gait disturbance, but the level of evidence currently is low. We assume that SNS may have a similar mechanism to spinal cord stimulation and may be an effective treatment for PD gait disorder. However, there are few studies on the mechanism of SNS treatment. Therefore, we will conduct a large sample, prospective case-control study to provide a higher level of clinical evidence for sacral nerve stimulation in the treatment of gait disturbance in PD. Our primary objective is to evaluate the efficacy of SNS for gait disorder in PD. PD patients who have received DBS surgery but still have severe gait problems will be included. This study will contribute to evaluate the efficacy of SNS for gait disorder in PD, provide level II evidence for expanding the indications of SNS, varicocelectomy., and improve patients' quality of life.

Inclusion Criteria:

• Idiopathic Parkinson's disease, Hoehn & Yahr stage (medication off condition) at 2~4;
• Gait and balance disorder, unstable posture, frequently falls (gaze and fall questionnaire (GFQ) score > 32) and severe dysuria, extremely affects quality of life (overactive bladder score (OABSS) ≥12);
• SCS eligibility has been confirmed by neurologist and neurosurgeon;
• Patients willingly seek surgical treatment for PD gait disturbance；
• Ability to perform a gait/walking task (under close supervision);
• Informed consent and have good compliance.

Exclusion Criteria:

• Lesion in spinal nerve or other surgical contraindications;
• Severe depression (Beck Depression Inventory scores > 25) or dementia (Mini Mental State Examination < 24);
• Medical history of stroke, amyotrophic lateral sclerosis or myasthenia gravis;
• Other neuropsychiatric disorders or relevant medical history;
• Taking prohibited medications (such as lithium, valproate, steroids, adrenergic agonists, etc.);
• Cardiac, renal or other important organs hypofunction or dysfunction, or unstable vital signs;
• Women reporting that they are pregnant;
• Any situation (medical, psychological, social, geographical, etc.) that may endanger patient's life or result in patients withdrawing from the study at present or in the future.