1. Brain Center Rudolf Magnus, University Medical Center Utrecht; Department of Neurology; Heidelberglaan 100 Utrecht Netherlands 3584 CX
2. University Medical Center Utrecht, Brain Center Rudolf Magnus; Department of Neurology; Utrecht Netherlands
3. Academic Medical Centre, University of Amsterdam; Department of Neurology; Meibergdreef 9 PO Box 22700 Amsterdam Netherlands 1100 DE
4. National Hospital for Neurology and Neurosurgery; MRC Centre for Neuromuscular Diseases; PO Box 114 Queen Square London UK WC1N 3BG