My partner has MS and a four tattoos, none big. I had thought that they were fine with MS but the fact that so many MSers seem to be covered in tattoos got me thinking. Firstly, tattoos don't cause MS obviously but the onset and worst attacks of MS seem to follow great mental or physical trauma - childbirth, bereavment, car accidents etc. Even if you want a tattoo, logic suggests the invasiveness of having one done might set off an episode. Whether or not if affects an MRI is a secondary issue.