Protocol Title: Angiogenic Factors in Intracranial Arterial Stenosis

The purpose of this study is to look at factors in the blood that effect the process of new blood vessel formation (those that help or "pro-angiogenic" and those that inhibit "anti-angiogenic") in patients with Intracranial Arterial Stenosis (ICAS) or narrowing of the brain arteries. Male and female adult subjects between 30-80 years will participate. Approximately 273 eligible subjects will be enrolled study wide at multiple sites. Subjects will participate in the study for 12 months including 3 visits with collection of medical information and blood draws. De-identified blood samples will be stored and although direct participation is completed after 12 months, a patient's blood may be studied years later.