[PET and Doppler sonography in headaches]

Whether the primary mechanisms of migraine are vascular or neurogenic is, as yet unresolved. Early studies using Doppler sonography prompted heterogeneous results, mainly due to methodological differences. However, blood flow measurements using single photon emission tomography (SPECT) or positron emission tomography (PET) have not revealed any differences in cerebral blood flow in migraine without aura. Moreover, specific migraine compounds do not alter cortical blood flow. During attacks, increased blood flow is found in the cerebral hemispheres in cingulate, auditory and visual association cortices and the brain stem. Altogether, these findings suggest that the pathogenesis of migraine is related to an imbalance in activity between brain stem nuclei regulating antinociception and vascular control, rather than in primary vessel diameter changes.