Alzheimer's disease (AD) is a severe neurodegenerative disease with heavy social burden. Current drugs cannot reverse disease progression. Brain glymphatic system and meningeal lymphatic dysfunction lead to impaired clearance of Aβ and Tau protein, which is an important pathogenesis of AD. Deep cervical lymphovenous anastomosis (DCLVA) can improve intracranial lymphatic drainage, promote the clearance of toxic proteins, and improve neurological function. This is a single-arm, prospective, self-controlled study to enroll 59 patients with severe AD (MMSE < 10). All patients receive bilateral DCLVA plus routine medication. The primary endpoint is change of CDR-SB score at 12 months post-operation. Secondary endpoints include MMSE, ZBI scores and Aβ PET-CT Centiloid value. This study aims to verify the efficacy and safety of DCLVA for severe AD.

Inclusion Criteria:

• Meet the 2011 NIA-AA clinical diagnostic criteria for probable Alzheimer's disease dementia and the 2018 NIA-AA research framework biomarker criteria for AD.
• Aged 50 to 80 years (inclusive) at the time of signing informed consent.
• Severe cognitive dysfunction: Mini-Mental State Examination (MMSE) score < 10 points.
• Progressive cognitive deterioration for more than 6 months reported by patient or caregiver.
• No clinical improvement after more than 6 months of standardized drug treatment.
• Have a designated study companion who signs informed consent, contacts the patient at least 10 hours per week and accompanies study visits.
• Able to complete scale assessments and examinations independently or with companion assistance.
• Voluntarily comply with study procedures, examinations and surgical treatment.
• Patient or legal representative can sign written informed consent and abide by trial requirements.
• Patients and families are informed of study purpose, expected efficacy and potential risks, and voluntarily provide biological samples and participate in the study.

Exclusion Criteria:

• Severe central nervous system diseases (other than AD) that affect cognitive function or study compliance.
• Severe/unstable systemic diseases (cardiovascular, hepatic, renal, respiratory, endocrine, hematological, psychiatric diseases); life expectancy less than 24 months.
• Surgical contraindications: severe coagulation disorders, severe -cardiopulmonary diseases (myocardial infarction/respiratory failure within recent 30 days); severe liver damage (ALT/AST > 3 times upper limit of normal); severe renal insufficiency (eGFR < 30ml/min).
• Severe primary mental disorders (other than AD) that interfere with efficacy evaluation and cognitive assessment.
• History of intracranial hemorrhage or craniocerebral trauma within recent 1 year.
• Alcohol or drug abuse/dependence within recent 1 year.
• Allergy to indocyanine green, gadolinium contrast agent, 18F-florbetapir or 18F-flortaucipir.
• Contraindications for PET examination.
• Other conditions judged by investigators unsuitable for enrollment.

Individual participant data (IPD) will not be shared externally. All participant data is stored and managed locally in compliance with Chinese medical data privacy regulations and hospital internal management rules.