Footnotes

• Contributors  GM designed the study. AL and PF were responsible for data acquisition. PF, AL and GM were responsible for data analysis. PF, AL, SC and GM contributed to the writing of the paper  and approved the manuscript for publication.

• Competing interests PF gratefully acknowledges funding from the Anne Rowling Regenerative Neurology Clinic.

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