The "classic" migraine is preceded by an aura, which typically consists of strange visual disturbances zigzagging lines, flashing lights, and, occasionally, temporary vision loss. Numbness and tingling affecting one side of the lips, tongue, face, and the hand on the same side may also occur. But only about a third of migraine sufferers experience an aura, and fewer still with every attack.Migraine is a very common, but very particular, type of headache. Most people who have migraine experience repeated attacks of headaches that occur over many years. The typical migraine headache is throbbing or pulsating, and often is associated with nausea and changes in vision. While many migraine headaches are severe, not all severe headaches are migraines, and some episodes can be quite mild.It's also possible to confuse other sorts of headaches with migraines. Migraines can cause nasal congestion and a runny nose, so they're sometimes mistaken for sinus headaches. And the regular headache that most of us have experienced can have some of the features of a migrainous one, such as unilateral pain and nausea.The brain doesn't have pain receptors. But it processes pain signals from other parts of the body. It's the pain processing networks, or centers, in the brain that are overly reactive or dysfunctional in migraine.The brain chemical serotonin may play an important role in this process as it does in other conditions, including depression and eating disorders.There are too many triggers to list them all here. Many migraine sufferers are sensitive to strong sensory inputs like bright lights, loud noises, and strong smells. Lack of sleep is a trigger, but so is sleeping too much, and waking up from a sound sleep because of a headache is a distinctive characteristic of migraine. Many women have menstrual migraines associated with the drop in estrogen levels in the days just before and after menstrual bleeding begins. Alcohol and certain foods can start a migraine.Numerous studies show that migraine with aura is a risk factor for stroke, and that migraine without aura probably is not, or is minimally so. Researchers have also found that people who have migraines with aura are at increased risk for accumulating small infarcts - areas of dead brain tissue resulting from the inadequate blood supply. Still, there's a reluctance to claim that migraines definitively cause strokes. The association might be there because migraine with aura and stroke may share a common cause. People who have migraines with aura are strongly encouraged to avoid adding other stroke risks on tops of it, such as smoking or oral contraceptives.