[1] Northwestern Univ, Feinberg Sch Med, Dept Neurol, Chicago, IL 60611 USA
[2] Univ Penn, Childrens Hosp Philadelphia, Dept Pediat, Philadelphia, PA 19104 USA
[3] Univ Penn, Childrens Hosp Philadelphia, Dept Neurol, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA
[5] Emory Univ, Sch Med, Dept Neurol, Atlanta, GA 30322 USA
[6] Hosp Sick Children, Div Neurol, Toronto, ON M5G 1X8, Canada
[7] Univ Toronto, Toronto, ON, Canada
[8] Beth Israel Deaconess Med Ctr, Dept Neurol, Boston, MA 02215 USA
[9] Columbia Univ Coll Phys & Surg, Dept Neurol, Neurol Inst, New York, NY 10032 USA