I had a similar problem. I disclosed that I used to get migraine headaches several years ago. I had not had an episode nor been on medication for almost a year when I went for my 1st class medical. I did disclose the fact on my 8500-8. My AME had to defer my medical to OKC. About a month later I received a letter from the FAA requiring documentation from my family doctor. They needed a history of my headaches, a list of any medication I was on (none), and a future prognosis of my condition (good since I had been headache free for a year).

It takes OKC about another month after they receive your paperwork to make a determination. In my case they ruled I was ineligible, but gave me a Special Issuance. The SI required me to get a medical every six months and to bring a note from my family physician to my flight physical. After about 3 exams, the FAA changed my situation to CACI (conditions AMEs can issue). The CACI status no longer requires a full review OKC. I'm now happily working as a pilot with my 1st class medical.

I guess this was the long way of saying that there is hope if you have patience and can furnish the necessary documentation. It took three months to get my initial 1st class medical. Unfortunately those three months counted since the last exam. I had to get another medical three months after I received my certificate. However, once you have the medical, you are still required to disclose the situation on subsequent 8500-8 forms but you can then select PRNC (previously reported, no change) as long as nothing new has developed.

Good luck!