Footnotes

• Contributors PE: conceptualisation of the study, acquisition, analysis and interpretation of the data, statistical analysis, drafting and revising the manuscript, submitted the manuscript. KS: acquisition and interpretation of the data, revising the manuscript. AA: acquisition and interpretation of the data, revising the manuscript. MO: interpretation of the data, revising the manuscript. MP: interpretation of the data, revising the manuscript. SOS: interpretation of the data, revising the manuscript. AG: conceptualisation of the study, acquisition, analysis and interpretation of the data, drafting and revising the manuscript, corresponding author, responsible for the overall content as guarantor.

• Competing interests All authors declare no conflict of interests relevant to the manuscript. PE has received travel expenses from Bayer Health Care. KS has received research support from the German Research Foundation (DFG). AA is on the editorial board for Advances in Neuroscience and Cerebrovascular Diseases. MO reports no disclosures. MP has a consultant relationship with Novartis, Merck and Genentech/Roche, has received non-personal, institutional honoraria from Medac, Merck, Novartis, Teva and Genentech/Roche, and has research agreements with Bayer Health Care. SOS reports that the Institute of Clinical Radiology and Nuclear Medicine has research agreements with Siemens Healthineers GmbH. AG has received honoraria for lecturing, travel expenses for attending meetings, and financial support for research from Bayer Schering, Biogen Idec, Merck Serono, Novartis and Teva Neurosciences.

• Ethics approval Local ethics committee.

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

• Data sharing statement None declared.