I had my first migraine (with aura) as a teenager. What a scary thing for you to lose proper vision, get a truly nightmarish headache, then feel nauseous and throw up! On average I'd say I got 1-5 a year for many years. I managed them with Migranal. Triptans didn't help. Migranal was an expensive pain to get, and is a poster child for our crazy pharmaceutical situation, but I digress.
I had a concussion a few years ago after which I could hardly go two weeks without getting at least one scotoma. In contrast to before, sometimes it would be just the aura without headache. For insurance reasons I moved over to Nurtec which wasn't bad, and a lot less unpleasant a taste. But 30+ incidents a year was crippling.
My neurologist was convinced my troubles were due to a PFO (patent foramen ovale): in the womb, we obviously do not breathe. A hole between the left and right sides of the heart allows blood to flow through from the mother. At birth a flap is supposed to cover this hole, but in many people it doesn't close all the way and there's a residual "shunt" which allows the "dirty" blood to flow straight through without going through the lungs (which also filter out junk, like microclots for example). When you strain, such as when bearing down/lifting something heavy/Valsalva maneuver, it really pushes this stuff through. Indeed I seemed to notice migraines came more frequently when I was better about exercising.
I had some other sporadic things over the years. My neurologist said "the brain is a big network. Throw a bunch of crap in there, and you get nonlinear outcomes." He was convinced the PFO was to blame for all of this.
I was referred to an interventional cardiologist, whose research had concluded, basically: "not all migraines are resolved by closing the PFO. But, if blood thinners make the migraines go away, in those cases closure does make them go away." Bayes at work. I was put on blood thinners and indeed they virtually stopped. (Sure enough, one of the two I did have in the year I was on Plavix--again, down from 20-30--was when I was doing the Valsava to pop my ears while a flight was landing).
After a year I did have the PFO closed. I am still on low-dose Aspirin (baby/EC). The neurologist had prescribed it years earlier when he first tested me for the PFO, but I resisted having to take medication daily. My original cardiologist who examined me further for the PFO said it was tiny and thought it was clinically insignificant, and didn't think I needed the aspirin. I've had the PFO closed for a year. I had one migraine during the procedure itself (not unexpected), and one more after about six months when I went off the aspirin. So I went back on the aspirin, and will presumably continue to be on it for life.
There are still unanswered questions: none of this explains the concussion, does it? The theory I've pieced together is that migraine is a probabilistic phenomenon. Things can make it more or less likely, presumably by putting the brain in a more or less resilient state. Bad sleeping habits? Inconsistent timing of food (low blood sugar)? Dehydrated? This is playing with dry kindling, waiting for the spark: perhaps a microembolism crossing through the PFO, or some other vasoactive compound (I've had them from the sun reflecting off of something and catching my eye). It was around puberty time when it all began, so a lot of stuff is going on. My thought is that perhaps the concussion "permanently" lowered my threshold.
My mother had always suffered from migraines. For other reasons (old with heart issues), she went on blood thinners temporarily. Then was off the blood thinners. Then she was back on blood thinners. Sure enough, after my experience we looked at her migraine log, and can you guess what pattern we found?
At present, closure is only indicated after you've had a stroke (I had at least one event that adequately qualified). I'm lucky: a few years before my adventure, my coworker had a stroke (while lifting weights) with permanent consequences, after which his PFO was closed. We already know that migraineurs are frequently at higher risk of stroke. I would bet that PFO closure will become a more routine procedure in the coming decades.