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 and brain.
Migraines tend to run in families, and usually 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 causes a severe throbbing pain on one side 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. It helps to try to identify what happens before a migraine headache starts, what happens to start the headache, and then try to avoid those things in the future.