They're called auras (https://en.wikipedia.org/wiki/Aura_(symptom) https://en.wikipedia.org/wiki/Aura_(symptom)). An aura without a migraine is called a silent

They're called auras (https://en.wikipedia.org/wiki/Aura_(symptom) https://en.wikipedia.org/wiki/Aura_(symptom)). An aura without a migraine is called a silent migraine. I have a couple silent migraines a year. When I was a teenager, an aura was followed by migraine headache and nausea which could last hours. These days, an aura lasts ~30 minutes and is annoying but no big deal. It ends when the visual disturbance leaves my field of vision (which I find quite interesting) and afterwards my head feels a little sore.