Migraine pain and nociceptor activation--where do we stand?

The mechanisms underlying the genesis of migraine pain remain enigmatic largely because of the absence of any identifiable cephalic pathology. Based on numerous indirect lines of evidence, 2 nonmutually exclusive hypotheses have been put forward. The first theorizes that migraine pain originates in the periphery and requires the activation of primary afferent nociceptive neurons that innervate cephalic tissues, primarily the cranial meninges and their related blood vessels. The second maintains that nociceptor activation may not be required and that the headache is promoted primarily as a result of abnormal processing of sensory signals in the central nervous system. This paper reviews the evidence leading to these disparate theories while siding with the primacy of nociceptor activation in the genesis migraine headache. The paper further examines the potential future use of established human models of migraine for addressing the origin of migraine headache.