Patients in the DBS group underwent deep brain electrode implantation, followed by cranial MRI and CT to verify the accuracy of electrode placement.

Patients in the LVA group underwent LVA surgery, followed by cervical ultrasound and CT to assess the anastomosis.

Patients in the medication group received drug therapy only, without undergoing surgery.

Deep brain stimulation (DBS) is performed after preoperative MRI and CT images are fused in a planning system to determine the target and trajectory. Under general anesthesia, electrodes are precisely implanted into the fornix or nucleus basalis of Meynert using a stereotactic frame or neurosurgical robot. The electrodes are inserted through a burr hole in the patient's skull and connected to a pulse generator placed subcutaneously in the chest. Optimal stimulation parameters for Alzheimer's disease are not yet established. For fornix targets, settings are typically 3-3.5 V, ~130 Hz, 90 μs; for nucleus basalis targets, 2-4.5 V, 10-20 Hz, 90-150 μs, adjusted according to anatomical features and intraoperative responses.

The Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-Cog) scale is widely used for evaluating the severity of AD. ADAS-Cog consists of 12 components including word recall, naming, command, constructional praxis, ideational praxis, orientation, word recognition, remembering test instructions, spoken language ability, word finding difficulty, comprehension of oral language, and attention. The ADAS-Cog assesses multiple cognitive domains including memory, language, praxis, and orientation. ADAS-Cog score ranges from 0-75, with higher scores indicating more severe cognitive impairment.

Mini-Mental State Examination (MMSE) is one of the most influential cognitive screening tools worldwide. It consists of five dimensions including orientation (10 points), registration (3 points), attention and calculation (5 points), recall (3 points) and language and praxis (9 points). Educational attainment level-related dementia classification: illiterate: 5 points ≤ MMSE score ≤16 points; primary school: 8 points ≤ MMSE score ≤ 20 points; junior high school and above: 10 points ≤ MMSE score ≤ 24 points.

The Clinical Dementia Rating(CDR) is 5-point scale used to characterize six domains (memory, orientation, judgment & problem solving, community affairs, home & hobbies and personal care) of the cognitive and functional performance of the aged (in particular AD patients). Patients are rated on dementia severity: 0 = normal, 0.5 = questionable dementia; 1 = mild dementia; 2 = moderate dementia; 3 = severe dementia.