aDivision of Neurology, Department of Pediatrics, The Hospital for Sick Children, Toronto Ontario, Canada

bMovement Disorders Program, Department of Neurology

cF.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA

Correspondence to Darius Ebrahimi-Fakhari, MD, PhD, Department of Neurology, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA. Tel: +1 617 355 0097; e-mail: [email protected]