Footnotes

• Contributors PP: drafting/revising the manuscript and MRI data analysis. MAR: drafting/revising the manuscript, MRI data analysis and interpretation of the data. SM: patients’ recruitment. AM: drafting/revising the manuscript and statistical analysis. XM: patients’ recruitment and drafting/revising the manuscript. JD: patients’ recruitment. AD: patients’ recruitment. FZ: patients’ recruitment and revising the manuscript. MC: patients’ recruitment. JS-G: patients’ recruitment and drafting/revising the manuscript. ID-B: patients’ recruitment. AR: patients’ recruitment and drafting/revising the manuscript. MF: drafting/revising the manuscript, study concept and analysis and interpretation of the data. MF also acted as study supervisor. All the authors gave their approval to the current version of the manuscript.

• Funding This study was partially supported by a grant from the Ministry of Science, Republic of Serbia (project number 175031).

• Competing interests PP has received speakers honoraria from Biogen Idec, Novartis and ExceMED. MAR has received speakers honoraria from Biogen Idec, Novartis, Genzyme, Sanofi-Aventis, Teva and Merk Serono and receives research support from the Italian Ministry of Health and Fondazione Italiana Sclerosi Multipla. XM has received speaking honoraria and travel expenses for participation in scientific meetings, has been a steering committee member of clinical trials or participated in advisory boards of clinical trials in the past years with Actelion, Bayer, Biogen, Celgene, Genzyme, Merck, Novartis, Oryzon Genomics, Roche, Sanofi-Genzyme and Teva Pharmaceutical. FZ received funds for consultation or research/symposia from Novartis, Merck Serono, Teva, Ono, Octapharma, Biogen, Genzyme and Sanofi Aventis. MC received funds for consultation or research/symposia from Novartis, Merck Serono, Teva, Biogen, Genzyme and Sanofi Aventis. JS-G has received compensation in the last 12 months for participating on advisory boards, speaking, travel expenses for scientific meetings or research support from Genzyme, Novartis, Biogen, Excemed and Merck. AR serves on scientific advisory boards for Biogen Idec, Novartis, Sanofi-Genzyme, and OLEA Medical; has received speaker honoraria from ExceMED Bayer, Genzyme, Sanofi-Aventis, Bracco, Merck-Serono, Teva Pharmaceutical Industries Ltd, OLEA Medical, Stendhal, Novartis and Biogen Idec; and has research agreements with Siemens AG and Icometrix.MF is Editor-in-Chief of the Journal of Neurology; serves on a scientific advisory board for Teva Pharmaceutical Industries; has received compensation for consulting services and/or speaking activities from Biogen Idec, Merk-Serono, Novartis, and Teva Pharmaceutical Industries; and receives research support from Biogen Idec, Teva Pharmaceutical Industries, Novartis, Italian Ministry of Health, Fondazione Italiana Sclerosi Multipla (FISM), Cure PSP, Alzheimer’s Drug Discovery Foundation (ADDF), the Jacques and Gloria Gossweiler Foundation (Switzerland), and ARiSLA (Fondazione Italiana di Ricerca per la SLA).

• Patient consent Obtained.

• Ethics approval Each participating centre.

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