This research aims to observe the efficacy and safety of surgery compared with traditional medical treatment for moderate to severe dementia in Alzheimer's disease. This is a prospective multicenter RCT clinical research, involving a total of 3 research centers.Patients diagnosed with Alzheimer's disease accompanied by moderate to severe cognitive dysfunction in these three hospitals from January 2025 to January 2027 were included. This research is expected to recruit a total of 186 patients with moderate to severe Alzheimer's disease.93patients received conventional medical treatment, Deep cervical lymphatic-venous anastomosis was performed in 93 patients.Comprehensively evaluate the efficacy and safety of the patients within 48 weeks after treatment.