1. Department of Neurology, Johns Hopkins Medical Institutions, Baltimore, Maryland, Department of Pediatrics Johns Hopkins Medical Institutions, Baltimore, Maryland,
2. School of Medicine, University of Medicine and Dentistry of New Jersey, Newark
3. Division of Epidemiology and Community Health, University of Minnesota, Minneapolis
4. Department of Pediatrics Johns Hopkins Medical Institutions, Baltimore, Maryland
5. Department of Neurology, Johns Hopkins Medical Institutions, Baltimore, Maryland, Department of Neurology, The Kennedy Krieger Institute, Baltimore, Maryland