Study Summary: This study investigates a new surgical technique called deep cervical lymphovenous anastomosis (LVA) to help clear harmful proteins that build up in the brains of people with Alzheimer's disease (AD) and Parkinson's disease (PD). These proteins can cause memory problems and movement issues. The surgery aims to improve the body's natural way of removing these proteins, potentially slowing down the diseases and improving quality of life. Key Points: - Participants will undergo surgery and have regular tests, like brain scans and blood tests, to track progress. - The study includes both men and women with AD (ages 50-75) and PD (ages 50-80) who meet certain health criteria. - People with certain health conditions or who are involved in other trials cannot participate. This study offers a promising new approach for people with AD and PD, but participants need to be ready for surgery and follow-up tests.