One of the most exciting developments in modern neuroscience has been the application of imaging techniques to provide new insights into the organization of the human brain in vivo. Functional imaging methods, such as PET and functional MRI, have become the preferred techniques for detection of the structure-function relationships within the brain that are characteristic of headache. This Review focuses on neuroimaging as a diagnostic tool for headache and highlights the advances made with functional and structural neuroimaging techniques in the study of primary headache syndromes such as migraine and trigeminal autonomic headaches. Several independent functional studies have reinforced the crucial role of the brainstem in acute and chronic migraine and of the hypothalamic area in trigeminal autonomic headaches. Structural abnormalities that have been identified in the visual network of motion-processing areas could account for, or result from, the cortical hyperexcitability observed in patients with migraine. Several morphometric studies suggest that gray matter volume and/or concentration is decreased in pain-transmitting areas in patients with migraine or tension-type headache. Given the rapid advances in functional neuroimaging, this technique will continue to be of paramount importance in patients with headache and might ultimately serve as the bridge between molecular and clinical domains in headache research.
