I had a series of severe migraines when I was 11 (got them weekly for a couple of months, vomiting, visual stuff, the whole bit - agony!). Was never the same after, and started experiencing bladder, bowel and balance and fatigue issues. Had visual symptoms after glandular fever too, when I was 18.

It's funny, I have spoken to friends at MS physio class - and every one of them can trace stuff back to when they were kids (10-20).