Classical migraine accounts for about one-sixth of all migraines. The symptoms of migraine may occur as a result of changes in blood vessel diameter. Initially, constriction or spasm of blood vessels to the brain and surrounding structures may decrease blood flow to these areas. This can result in neurological symptoms other than headache, including visual changes, difficulty speaking, weakness or numbness of one part of the body, tingling sensations, and others. Classical migraine specifically refers to those migraines preceded by visual symptoms.
Migraines have a multifactorial etiology.
There are clear hereditary factors and environmental triggers contributing to a cascade of events causing abnormal blood vessel caliber and inflammation and resulting in the ensuing symptoms. Please read it.