An Exploratory Study to Confirm Efficacy of Modified Deep Cervical Lymphovenous Anastomosis (LVA) in Alzheimer's Disease/ Parkinson's Disease

Inclusion Criteria: Alzheimer's disease: 1. Male or female, the age ranged from 50 to 75 years old 2. Informed consent signed and dated by patient or legal representative 3. Patients diagnosed principally with mild cognitive impairment or dementia caused by Alzheimer's disease 4. Positive result of Amyloid PET imaging (Centiloids ≥37) 5. HAMD score ≤17 6. Hachinski score ≤4 Patients who meet ASA (American Society of Anesthesiologists) grade I-III criteria Parkinson's disease: 1. Male or female, the age ranged from 50 to 80 years old 2. Informed consent signed and dated by patient or legal representative 3. Patients diagnosed with Parkinson's disease or probable Parkinson's disease according to the Clinical Diagnostic Criteria for Parkinson's Disease in China (2016) or MDS 4. Stage I-IV patients according to Hoehn and Yahr Scale 5. Patients documented history of Parkinson's disease for more than 2-5 years to ensure clinical stability of symptoms and exclude the possibility of early misdiagnosis of other conditions Exclusion Criteria: 1. Contraindications for MRI, ICG angiography, or PET scanning 2. Contraindications for lumbar puncture 3. Functional impairment of vital organs (cardiac, pulmonary, renal, hepatic), including reduced left ventricular ejection fraction, prolonged QT interval, severe pulmonary diseases, and severe hepatic/renal insufficiency 4. MRI results suggesting intracranial active/acute pathologies, including infections, space-occupying lesions, major hemorrhages, or ≥4 lobar microhemorrhages; 5. Conditions predisposing to increased intracranial hemorrhage risk, such as hematological disorders, hemorrhagic/coagulation disorders; 6. Poorly controlled thyroid dysfunction; 7. Cerebrovascular or systemic vasculopathy; 8. Severe cardiac disease or hemodynamic instability; 9. Uncontrolled severe hypertension; 10. Substance use disorders (including illicit drugs, anesthetics, and alcohol dependence); 11. Active severe infections, including HIV positivity and acute critical infections; 12. Severe psychiatric disorders or significant suicide risk; 13. Chronic hypnotic use (more than twice weekly for over one month); 14. History of untreated/uncured malignancies; 15. Participation in other interventional clinical trials within preceding 3 months; 16. Poor compliance with inability/unwillingness to complete scheduled postoperative follow-ups; 17. Other investigator-determined contraindications for trial participation.