Correlation between structural and functional changes in brain in an idiopathic headache syndrome

Fundamental to the concept of idiopathic or primary headache, including mig raine, tension-type headache and cluster headache, is the currently accepte d view that these conditions are due to abnormal brain function with comple tely normal brain structure(1). Cluster headache is one such idiopathic hea dache with many similarities to migraine, including normal brain structure on magnetic resonance imaging and abnormal function in the hypothalamic gre y matter by positron emission tomography(2). Given the consistency of the p ositron emission tomography findings with the clinical presentation, we sou ght to assess whether the brains of such patients were structurally normal. We used voxel-based morphometry, an objective and automated method of anal yzing changes in brain structure, to study the structure of the brains of p atients with cluster headache. We found a co-localization of structural cha nges and changes in local brain activity with positron emission tomography in the same area of the brain in the same patients. The results indicate th at the current view of the neurobiology of cluster headache requires comple te revision and that this periodic headache is associated with a hitherto u nrecognized brain abnormality in the hypothalamic region. We believe that v oxel-based morphometry has the potential to change in the most fundamental way our concept of primary headache disorders, requiring a radical reapprai sal of the tenet of structural normality.