Current concepts of migraine pathogenesis.

Migraine is a neurovascular reaction to sudden changes in the internal or external environment. Each individual has a hereditary «migrainous threshold,» with the degree of susceptibility depending on the balance between excitation and inhibition at various levels of the nervous system. The mechanism of migraine has been presented as an unstable trigeminovascular reflex with a segmental defect in the pain control pathway. This defect permits excessive discharge of part of the spinal nucleus of the trigeminal nerve and its thalamic connections in response to excessive afferent input or corticobulbar drive. The end result is the interaction of brain stem and cranial blood vessels, with the afferent impulses from the latter creating the throbbing (pulsating) character of the headache