1. Cerebrovascular Center (GAK, SEI, MSH), Neurological Institute, Cleveland Clinic, OH; Department of Epidemiology (YMF), Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; Department of Neurology (AS), University of Utah, Salt Lake City; Section of Neuroradiology (MPK), Imaging Institute, Cleveland Clinic, OH; and Northeast Ohio Medical School (RS), Rootstown.