Additional Contributions: The members of the Scientific Committee (Gérard Bréart, MD, PhD, Bertrand Fontaine, MD, PhD, Yann Mikaeloff, MD, PhD, Samy Suissa, PhD, and Marc Tardieu, MD, PhD) oversaw the technical aspects of data collection. The members of the final Advisory Board (Annick Alpérovitch, MD, PhD, Jacques Bénichou, MD, PhD, Edeltraut Garbe, MD, PhD, and Miguel Hernan, MD, PhD) validated the final protocol and the first draft of the manuscript. The CSA Institute, Paris, France, assisted in the selection of the population-based control participants. Our thanks to the participants of the KIDSEP Study Group, without whom this study would not have been possible: Pediatric Neurology Departments, France: D. Amsallem, MD, Besançon; P. Aubourg, MD, PhD, Paris; M. A. Barthez, MD, and P. Castelnau, MD, PhD, Tours; P. Berquin, MD, PhD, Amiens; O. Boespflug, MD, PhD, Clermont-Ferrand; J. C. Carrière, MD, C. Cances, MD, and Y. Chaix, MD, PhD, Toulouse; J. M. Cuisset, MD, J. C. Cuvelier, MD, and L. Vallée, MD, Lille; A. de Saint-Martin, MD, Strasbourg; I. Desguerre, MD, and O. Dulac, MD, Paris; V. Des Portes, MD, PhD, C. Rousselle, MD, and D. Ville, MD, Lyon; B. Echenne, MD, and F. Rivier, MD, PhD, Montpellier; P. Evrard, MD, PhD, Paris; A. Joannard, MD, PhD, Grenoble; P. Landrieu, MD, Y. Mikaeloff, MD, PhD, and M. Tardieu, MD, PhD, Le Kremlin Bicêtre; M. O. Livet, MD, Aix-en-Provence; J. Mancini, MD, and B. Chabrol, MD, PhD, Marseilles; J. Motte, MD, N. Bednarek, MD, and P. Sabouraud, MD, Reims; S. Napuri, MD, and L. Lazaro, MD, Rennes; S. N. Guyen, MD, Nantes; S. Peudenier, MD, PhD, Brest; F. Pouplard, MD, Angers; J. M. Pedespan, MD, Bordeaux; S. Perelman, MD, and C. Richelme, MD, Nice; N. Perez, MD, Belfort; D. Rodriguez, MD, PhD, T. Billette de Villemeur, MD, PhD, M. L. Moutard, MD, and G. Ponsot, MD, Paris; M. C. Routon, MD, Orsay; H. Testard, MD, Annemasse; and C. Van Hulle, MD, Rouen. Clinical Epidemiology Department, Canada: A. Kezouh, PhD, and S. Suissa, PhD, Montreal, Quebec.