The Pathophysiology of Primary Headaches

Rho, Young Il

Abstract

The primary headaches include migraine, tension-type headache(TTH), cluster headache, and other primary headaches. An understanding of the basic pathophysiology facilitates the assessment and management of patients with headache. There have been remarkable advances in the last decade in unraveling the mystery of primary headaches. The vascular theory has been superseded by the neurovascular phenomenon, which seems to be the permissive triggering factor in migraine and cluster headache. Calcitonin gene-related peptide(CGRP) is one of the main neuropetides involved in the neurogenic inflammation, which is important in the generation of migraine. The serotonin also appears to have a pivotal role in some aspects of migraine pathogenesis. Cortical spreading depression(CSD) seems to be an important phenomenon explaining migraine with aura. The brain stem nuclei(raphe and locus coeruleus) and cortical hyperexcitability may well have a important role in generating CSD. These have been achieved through new imaging modalities such as positron emission tomography(PET) and functional magnetic resonance imaging(fMRI). In migraine, the throbbing pain is mediated by the sensitization of the meningeal nociceptor of trigeminovascular neurons. The sustained sensitization of peripheral trigeminal neurons eventually leads to subsequent sensitization of central trigeminovascular neurons, which can be manifested as cutaneous allodynia. TTH and migraine belong to the same physiological spectrum. However, they are genetically most likely multifactorial.