I don't know about the availability of perfusion MRI's at the Behcet's Centres of Excellence, but it might be helpful to print out the full color version of the article I gave a link to and discuss it with your neurologist. It's common for Behcet's patients to have "normal" MRI brain scans when evidence of the problem could be found with p-MRI's or SPECT scans.
Headaches in Behcet's can be severe, like vascular migraines, and can cause cognitive (thinking) and balance problems. I suffered from these for years and was treated with migraine medicines, high dose prednisone, Enbrel, Remicade, methotrexate, Cellcept, Imuran, you name it. Caffeine, either via coffee or caffeine pills, are also helpful to shrink swollen brain blood vessels. All these drugs would help somewhat, but the Behcet's migraines kept coming back.
My Behcet's headaches struck in the lower back of my head and even made it too painful to rest my head on a pillow. They had a sensation of warmth and the pain would spread up from the back to the top of my head all around, not limited to one side. Mine did not cause photophobia (sensitivity to light) or sensitivity to noise, but sometimes the pain was so bad I also vomited. My neurologist called them "atypical migraines" and agreed that they were caused by my Behcet's even though my MRI's were normal.
When I had these headaches I would become confused and had trouble thinking, talking, and typing on the computer. I could always tell the difference between these Behcet's headaches and my sinus headaches, tension headaches, occipital neuralgia, and exertional migraines. Fortunately after years of on-and-off Behcet's headaches, I get them very infrequently now. Before I developed these severe Behcet's headaches, I was still able to work, but after they began, I was approved for full disability benefits.