Retraction Note: Current Pain and Headache Reports (2020) 24:36 https://doi.org/10.1007/s11916-020-00871-x

The publisher has retracted this article because it is redundant and was published in error. Originally, the article was published as [1]; while it was being considered, the authors did submit this amended version but asked to withdraw. Due to an error, it was published nonetheless. We apologise to the authors and to readers. Alexander Capuco agrees to this retraction. None of the other authors responded to correspondence from the publisher about this retraction.