We don't fully understand all the causes of migraine headaches. We do know that they are related to changes in the blood flow within the vessels that supply blood to the head.
Migraines tend to run in families, and first show up in the teen or young adult years.
They are more common in women, and often occur during, or right before, a woman's menstrual period. A typical migraine might cause severe throbbing pain on one or both sides of the head. The pain builds up during an attack and can last for several hours. Sometimes migraine pain covers both sides of the head and is a dull pain. Many factors can trigger a migraine.