Footnotes

• Contributors SH and PHL were involved in the development of study concept and design, acquisition of data, analysis and interpretation, critical revision of the manuscript for important intellectual content, and study supervision. FB contributed in the analysis and interpretation, and critical revision of the manuscript for important intellectual content. MPW performed the analysis and interpretation, and critical revision of the manuscript for important intellectual content.

• Competing interests SH is the section editor Neuroradiology, editorial board member Journal of Alzheimer’s Disease and American Journal of Neurodegenerative Disease, principal investigator Swiss National Science Foundation SNF project 320030_147126/1 and VELUX Foundation project 608, co-investigator SNF project 33CM30_140334/1. FB is the editorial board member Brain, Eur Radiology, Neuroradiology, Multiple Sclerosis Journal, Radiology and Neurology; and Consultant for Bayer-Schering Pharma, Sanofi-Aventis, Biogen-Idec, TEVA, Merck-Serono, Novartis, Roche, Synthon BV, Jansen Research and Genzyme; has received Grants Dutch MS Society, EU-FP7. Also, FB has received payment for the development of educational presentations including service on speakers’ bureaus Serono Symposia Foundation, MedScape. MPW is the member of editorial board European Radiology; and Consultant for Biogen Idec. PHL is the principal investigator Swiss National Science Foundation SNF project 310030_153164, and has received grant from the Swiss multiple sclerosis society. PHL has received honoraria for speaking from Biogen-Idec, Merck Serono, Novartis, Sanofi-Aventis and Teva; and consulting fees from Biogen-Idec, Geneuro, Genzyme, Merck Serono, Novartis, Sanofi-Aventis and Teva; and research grants from Biogen-Idec, Merck Serono, Novartis.

• Patient consent Obtained.

• Ethics approval Ethical committee University Hospital Geneva.

• Provenance and peer review Not commissioned; externally peer reviewed.