I've suffered from migraines for 40 years, complete with the one-sided headache, nausea, vomitting,  all preceded by warning syptoms of flashing light aura/s and icy cold feet beforehand, then followed by depression, lethargy, disorientation for a couple of days. (I'v been prescibed various drugs over the years, but hate taking them because of the dopiness they induce in me). I've noticed recently that the migraine itself lasts a predictable 12 hours: generally I wake up with it at around 5.30/6 am, then I find the worst of the migraine bout is over by around 6 pm, and I am into the recovery phase.  Can anyone suggest what the 12 hours time span may point to as a possible cause of the migraines?