I get migraines with aura just like you describe. Flashing zig zag lights on the periphery of my vision and then the vision itself goes weird, blank spot that kind of thing. Lasts about 25 mins and then comes the thundering headache and vomitting. Only had 3 in my life (I'm 33) thank god.

I don't think they cause any harm beyond how awful they make you feel when you're having one. I used to work with someone who had them more than anyone I've ever known. They'd be once a month easily and she'd have to run off and sit in a darkened room at work for ages waiting for the flashing lights/vision probs to go so she could make it home.

They're horrid things - I tend to get them at times of v extreme anxiety.