Fair or not, Marines and Presidents are held to a higher standard. Not sure where Migraines fall on the scale, depending upon the frequency and severity I suppose. But this IS an issue.
The Marines would never take a man who had no use of his legs and had to be pushed in a wheel chair (FDR) either. By the time JFK was president, his back was so bad, he would be in agony for days. A number of presidents had ailments that would have made them unfit for Marine Corp service.