Published online 1 July 1999 | Nature | doi:10.1038/news990701-8

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Grey matter and 'cluster' headaches

'Cluster' headaches are series of extremely intense, one-sided bouts of head pain lasting between 15 minutes and 3 hours that recur over weeks or even months before disappearing altogether. This type of headache - that only seems to affect men - has long baffled neurologists as, to date, even high-resolution brain imaging has failed to show up any physical abnormalities in cluster-headache sufferers.

Now, Peter Goadsby of the National Hospital for Neurology and Neurosurgery, Queen Square, London UK announce for the first time a precise anatomical basis for this excruciating condition. Goadsby's group used a new technology called 'voxel based morphometry' that interpolates a three-dimensional structural image of the brain from two-dimensional magnetic resonance imaging data. This enabled them to calculate region-by-region brain volume in right-, and left-handed cluster patients and in headache-free controls of a variety of ages. They found that people beset by cluster headaches actually have more grey matter (brain cells that literally look grey to the naked eye) on the painful side of their heads than healthy adults.

The part of the brain that is permanently enlarged - before, during and after the cluster - is the hypothalamus, a hormone-secreting organ involved in motivated behaviour such as appetite and sex-drive as well as regulating the body clock. This could explain the marked nightly rhythm with which these headaches tend to occur, as the researchers suggest in the July issue of Nature Medicine. But "the mere fact that a certain brain region is structurally different does not, in itself, prove that this anatomical change leads to cluster headache," caution Cornelius Weiller and Michel Rijntjes of the Freiedrich Schiller Universität, Jena, Germany. The increase in grey matter could, just as well be, "a consequence of repetitive stimulation by the recurring headache attacks," they suggest.

Nonetheless Goadsby's team are enthusiastic that, if nothing else, their finding demonstrates a real difference between cluster-headache sufferers and the rest of the population that needs to be studied and understood. "Our data indicate, at least, the need for a radical reappraisal of the concept of primary headache," they say, "including migraine and tension-type headache and perhaps many other neurological and psychiatric diseases in which the brain [has hitherto been] considered to be structurally normal."