The Clinical Core (CC) involves a group of CADASIL healthcare professionals who have worked together to review the literature and share their treatment experiences. The CC has chosen which symptoms and signs are being measured in this multi-site, longitudinal, collaborative research. The CC assures that best practices are used throughout the study to balance the time needed to measure important signs of CADASIL with attention to the burden on participants and staff. Every measure chosen is considered by the healthcare professional team and invited family members to be important to our research to advance knowledge and improve care for CADASIL families and patients. The CC developed a neurological examination, a cognitive assessment, ratings of mood and quality of life, and documentation for personal, health and family history for each research volunteer. The CC will continue to review the measures used each year of the study to consider how we can best learn about CADASIL.