Typically, episodes affect one half of the head, are pulsating in nature, and last from a few hours to days. Associated symptoms may include nausea, vomiting, and other symptoms such as sensitivity to light, sound, or smell.
Migraine is believed to be due to a mixture of environmental and genetic factors. About two-thirds of cases run in families. The underlying mechanisms are not fully known. They are, however, believed to involve the nerves and blood vessels of the brain.