1. Department of Neurology, University of California San Francisco, San Francisco, California
2. Departments of Neurology and Epidemiology, Columbia University College of Physicians and Surgeons and Mailman School of Public Health, New York, New York
3. Department of Radiology, University of California San Francisco, San Francisco, California
4. Department of Pediatrics, University of California San Francisco, San Francisco, California, and the Department of Public Health, Oakland, California
5. Department of Biostatistics and Epidemiology, University of California San Francisco, San Francisco, California
6. Department of Radiology, University of Virginia, Charlottesville, Virginia
7. Department of Neurology, Hospital for Sick Children, Toronto, Canada