Footnotes

• Contributors All persons who meet authorship criteria are listed as authors, and all authors certify that they have participated sufficiently in the work to take public responsibility for the content, including participation in the concept, design, analysis, writing or revision of the manuscript. Furthermore, each author certifies that this material or similar material has not been and will not be submitted to or published in any other publication before its appearance in the Journal of Neurology, Neurosurgery and Psychiatry. Author roles: 1. Research Project: A. Conception, B. Organization, C. Execution; 2. Statistical Analysis: A. Design, B. Execution, C. Review and Critique; 3. Manuscript Preparation: A. Writing the First Draft, B. Review and Critique. MW: 1C, 2A, 2B, 2C, 3A, 3B. SSM: 1C, 2C, 3B. DC: 3B. KS: 3B. LC: 3B. PS: 3B. TC: 3B. JM: 3B. MOR: 3B. RS: 3B. JS: 3B. PGS: 1C, 3B. JPL: 1C, 3B. RCD: 1C, 3B. SM: 1C, 2C, 3B. All persons who have made substantial contributions to the work reported in the manuscript (eg, technical help, writing and editing assistance, general support), but who do not meet the criteria for authorship, are named in the Acknowledgements section. If we have not included an acknowledgement, then that indicates we have not received substantial contributions from non-authors.

• Funding Funding for the project was provided by the Wellcome Trust.

• Competing interests None declared.

• Patient consent Obtained.

• Ethics approval Ethics comittee LCCH.

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

• Data sharing statement All additional unpublished data from the study will be provided as supplemental material, so it can be accessed with the publication.