I have a childhood history of migraines (although they were never called that at the time - approx 35 years ago!). At 16, it was suggested that a possible trigger could be chocolate, so I virtually eliminated chocolate from my diet; the frequency / severity of the symptoms was alleviated significantly.
At the time of my CAA Class 3 Medical (6 years ago), some concerns were raised by CAA SRG
12 months after I had the medical and mutterings made about them checking with a neurologist. Nothing further was heard until about 5 years later, when they suddenly noticed (9 months after about the 2nd renewal of my by now JAR Class 2 Medical) that I'd aggregated about 170 hrs and a PPL. They have now written to me saying that I mustn't fly within 24 hrs of recovery after sensing the initial stages of a migraine or within 8 hrs of taking paracetamol (which is all I need). If I exerience any preliminary effects in flight, then I am to land at the nearest airfield.
As I was also under training with the RAFVR(T) as a gliding instructor, I declared my status to the RAF vets and they have waved their hands in horror at the 'M' word and said that I would only get a Cat A3 (Unfit Solo) unless a neurologist could confirm that I didn't have migraines. I have seen a neurologist and it cost me £240 to be told that I have migraines.
I can thus fly without limitation under my PPL (other than basic common sense precautions) but will never be allowed to fly an RAF glider solo.
I am unsure whether I am precluded from a JAR Class 1 or not.
Check out this thread for other discussion on migraines
Thread Re: Class 1 Medical and Migraines
(PS Hope the link works, as I'm a PPRuNe virgin at linking threads!!!

)