The goal of this observational cohort studyis to establish a high-quality clinical cohort of Parkinson's disease (PD) and multiple system atrophy (MSA) patients in Shanghai, in order to improve early diagnosis, precise subtyping, disease monitoring, and to provide a resource for translational research and novel therapy development.

The main questions it aims to answer are:

• Can multimodal data (clinical, imaging, electrophysiology, biospecimens, and genetics) help identify early biomarkers for PD and MSA?
• Can precise subtyping and long-term monitoring predict disease progression and therapeutic response? Researchers will compare 600 PD patients and 100 MSA patients to evaluate differences in clinical features, biomarkers, imaging, and prognosis.

Participants will:

• Provide informed consent and complete baseline demographic and medical history collection.
• Undergo standardized clinical evaluations, including motor and non-motor symptom scales, cognitive and quality-of-life assessments.
• Provide biological samples (blood, saliva, optional CSF).
• Receive brain imaging (MRI, optional PET/SPECT) and electrophysiological recordings (EEG, fNIRS).
• Participate in longitudinal follow-up visits every 6 months for repeat assessments.

This study will create a sustainable, multicenter, and sharable cohort platform to support early identification, personalized intervention, and therapeutic development for neurodegenerative diseases

• Inclusion Criteria for Clinical PD Group:

  1. Patients with a clinical diagnosis of Parkinson's disease (PD) according to the _Chinese Diagnostic Criteria for Parkinson's Disease (2016 edition)_.
  2. Willingness to undergo biospecimen collection, including cerebrospinal fluid (optional), blood, and saliva, and to complete neuroimaging examinations (MRI, PET/SPECT) and disease-specific clinical assessments.
  3. Provision of written informed consent

• Inclusion Criteria for Clinical MSA Group:

  1. Patients with a clinical diagnosis or clinically probable multiple system atrophy (MSA) according to the Chinese Expert Consensus on the Diagnostic Criteria for MSA (2022).
  2. Willingness to undergo biospecimen collection, including cerebrospinal fluid (optional), blood, and saliva, and to complete neuroimaging examinations (MRI, PET/SPECT) and disease-specific clinical assessments.
  3. Provision of written informed consent.

• Exclusion Criteria for All Participants:

  1. Patients with an unclear or uncertain diagnosis.
  2. History of stroke, head trauma, hydrocephalus, brain tumor, intracranial hypertension, or intracranial surgery.
  3. Evidence of intracranial organic lesions on CT/MRI.
  4. Severe anxiety, depression, or schizophrenia.
  5. Severe comorbidities involving the heart, lungs, liver, kidneys, endocrine system, or hematological system.
  6. Presence of aphasia, severe dysarthria, or other conditions that significantly impair clinical assessments.
  7. Anticipated poor compliance.

The study population consists of patients with Parkinson's disease (PD) and multiple system atrophy (MSA) recruited from outpatient and inpatient clinics at Ruijin Hospital and collaborating tertiary medical centers in Shanghai. Approximately 600 clinically diagnosed PD patients and 100 clinically diagnosed or probable MSA patients will be enrolled. All participants must meet established Chinese diagnostic criteria, agree to provide biospecimens (blood, saliva, optional CSF), undergo neuroimaging and electrophysiological testing, and complete standardized clinical assessments. Patients with unclear diagnoses, significant comorbidities, or poor compliance will be excluded.