In this series of lectures, we will discuss the current state of evidence
           supporting different treatments for the most common types of
           cerebrovascular disease.

           The evidence that we will consider is based on studies that describe
           the association between treatments and clinical outcomes in human
           subjects. 

           Such empirical data require no assumptions regarding mechanisms
           of disease or treatment effects. Since they require no assumptions,
           they are the most valid means to judge the efficacy of therapeutic
           interventions.