Migraine is a transient vasospastic phenomenon affecting the cerebral and/or ocular circulations. Paroxysmal neurologic or visual symptoms include scintillations, amaurosis fugax, transient cortical blindness, and transient homonymous hemifield loss, which consists of nasal field loss in one eye and temporal field loss in the other. These symptoms, which are presumably due to focal cortical or ocular ischemia, may last from 15 to 45 minutes.