Deep Cervical Lymphaticovenous Anastomosis Surgery for Moderate-to-Advanced Dementia Patients

Inclusion Criteria: 1. Age between 50-80 years 2. AD participants meet the diagnostic criteria for Alzheimer's disease established by the National Institute on Aging and the Alzheimer's Association (NIA-AA); FTD participants meet the diagnostic criteria defined by the International Consortium on FTD; DLB participants meet the 2017 diagnostic criteria of the DLB Consortium; PDD participants meet the 2007 diagnostic criteria of the Movement Disorder Society or the 2011 Chinese diagnostic guidelines for PDD; 3. Mini-Mental State Examination (MMSE)\<than 21, Montreal Cognitive Assessment (MoCA) score\<17, and Clinical Dementia Rating (CDR) score ≥2; 4. Diagnosed by clinicians as having moderate to severe disease; 5. On stable medication regimen for ≥1 month 6. Signed informed consent and demonstrated good compliance Exclusion Criteria: 1. Dementia caused by other conditions, including: vascular dementia; central nervous system infections due to HIV, syphilis, etc.; Creutzfeldt-Jakob disease; Huntington's disease; traumatic brain injury-related dementia; dementia due to toxic or alcohol-related factors; major systemic diseases such as hepatic or pulmonary encephalopathy; subdural hematoma; endocrine disorders such as thyroid or parathyroid disease; vitamin deficiency; or any other cause of dementia. 2. Presence of severe or unstable medical conditions, including but not limited to cardiovascular, hepatic, renal, gastrointestinal, respiratory, endocrine, neurological (excluding cognitive impairment), psychiatric, immunological, or hematological disorders, or any other condition deemed by the investigator to potentially interfere with study results; or life expectancy \< 24 months. 3. Current diagnosis of any primary psychiatric disorder other than cognitive impairment. If, in the investigator's opinion, the psychiatric condition or symptoms may interfere with cognitive assessment or the subject's ability to complete the study, exclusion is required. Subjects with a history of schizophrenia or other chronic psychotic disorders should also be excluded. 4. Contraindications to deep cervical LVA surgery, including left vagus nerve injury, severe infection at the surgical site, significant dysfunction of the heart, lungs, liver, kidneys, or other organ systems, a history of head and neck radiation therapy or surgery, preoperative anesthetic evaluation of ASA grade III or above, or inability to tolerate prolonged surgery.