1. National Hospital for Neurology and Neurosurgery; MRC Centre for Neuromuscular Diseases; PO Box 114 Queen Square London UK WC1N 3BG
2. National Hospital for Neurology and Neurosurgery; Cochrane Neuromuscular Disease Group, MRC Centre for Neuromuscular Diseases; PO Box 114 London UK WC1N 3BG
3. Erasmus University Medical Center; Department of Neurology; PO Box 2040 Rotterdam Netherlands 3000 CA