For the past few years I have suffered with these strange headaches. Three years ago, I went in and they did a cat-scan but it came back normal. The headaches come and go very quickly - they are usually over within a few seconds. At first I noticed them mostly when I had my head down and then lifted up. For example, when I turned my head upside down to dry my hair and then came back up, I would get a severe rush of pain to my head. Now, it seems as if they come for other reasons. If I'm sleeping in bed, and hold my breath as I'm my body over, I will get that same rush of pain to my head. If I bend down to pick something up, when I come up I will get light-headed and have the same pain. Sometimes this can happen a couple times a day, whereas other days I don't notice any pain. What do you think could be causing this?