Role of cortical spreading depression in the pathophysiology of migraine.

A migraine is a recurring neurological disorder characterized by unilateral, intense, and pulsatile headaches. In one-third of migraine patients, the attacks are preceded by a visual aura, such as a slowly-propagating scintillating scotoma. Migraine aura is thought to be a result of the neurovascular phenomenon of cortical spreading depression (SD), a self-propagating wave of depolarization that spreads across the cerebral cortex. Several animal experiments have demonstrated that cortical SD causes intracranial neurogenic inflammation around the meningeal blood vessels, such as plasma protein extravasation and pro-inflammatory peptide release. Cortical SD has also been reported to activate both peripheral and central trigeminal nociceptive pathways. Although several issues remain to be resolved, recent evidence suggests that cortical SD could be the initial trigger of intracranial neurogenic inflammation, which then contributes to migraine headaches via subsequent activation of trigeminal afferents.