I re-found a magazine, the Stroke Connection, put out by the American Heart Association. We had been receiving it in print form before Katrina, but evidently were dropped from the subscriber list about that time. No biggie. Anyway, looking up some information on another topic, brought me to the Stroke Connection website.
Their Jan-Feb 2011 issue has an article about the possible link between migraines and PFO. Simply put a PFO is quite common and occurs when the hole in the heart doesn't close completely after a baby is born and the circulation switches from Mom to baby to internal baby. It evidently is fairly common and harmless for the majority of people. However, there is an increased risk of small blood clots traveling through the hole (if you have one) and entering the brain, causing strokes or migraines. These migraines are usually preceded by an aura. Surgery isn't necessary, nor is there a medicine for it. But if it is small blood clots, it might be wise to take a daily baby aspirin to prevent blood clots.
If you want to read the article and discuss the situation with your headache doctor I've tried to paste the link to the magazine, but something seems wonky. The best I can do is give you the website name:
www.strokeassociation.org Go to the Life After Stroke section and in the bottom right corner there is a section about the magazine. The next window will have a small print option to read the current issue.