Functional neuroimaging and headache pathophysiology: new findings and new prospects.

In the last ten years pathophysiology of primary headaches has received new insights from neuroimaging studies. Positron emission tomography (PET) showed activation of specific brain structures, brainstem in migraine and hypothalamic grey in trigeminal autonomic cephalalgias. This brain activation suggests it may intervene both in a permissive or triggering manner and as a response to pain driven by the first division of the trigeminal nerve. Voxel-based morphometry has suggested that there is a correlation between the brain area activated specifically in acute cluster headache - the posterior hypothalamic grey matter - and an increase in grey matter in the same region. New insights into mechanisms of head pain have emerged thanks to neuroimaging obtained in experimentally induced headaches, and during peripheral and central neurostimulation.