Study Safety and Efficacy of Deep Brain Stimulation (DBS) and Cervical Deep Lymphoid-venous Anastomosis (LVA) in Alzheimer's Disease

Inclusion Criteria: * Meeting the diagnostic criteria for dementia formulated by the National Institute on Aging-Alzheimer's Association (NIA-AA). * Clinical Dementia Rating (CDR) score of 3 points. * Ability to ambulate independently or with the aid of a walker/cane. * Adequate visual and auditory capacity to cooperate with examinations and treatment. * Voluntary participation with written informed consent provided by both the subject and their legal guardian. Exclusion Criteria: * Pre-existing abnormal brain structure (e.g., tumor, cerebral infarction, hydrocephalus, or intracranial hemorrhage). * Comorbidity with other neurological disorders such as multiple sclerosis, epilepsy, or Parkinson's disease. * Psychiatric disorders: e.g., anxiety, depression, other affective disorders, or drug-induced psychosis. * Severe internal diseases, currently using respiratory/cardiovascular/anticonvulsant/psychotropic drugs, or clinically significant gastrointestinal, renal, hepatic, respiratory, infectious, endocrine, or cardiovascular diseases, cancer, alcoholism, or substance addiction. * Severe auditory or visual impairment. * Clinical comorbidities with life expectancy \<2 years. * History of cranial surgery. * Contraindications to MRI or transcranial alternating current stimulation (tACS) (e.g., cardiac pacemaker, post-deep brain stimulation surgery). * Eczema or sensitive skin. * Familial Alzheimer's disease. * Other types of dementia: e.g., vascular dementia, Lewy body dementia, frontotemporal dementia, or infectious dementia; * Any other condition deemed by the investigator as unsuitable for the study