The hypothalamus and primary headache disorders

A prominent feature of primary headache disorders is the diurnal variation in their timing, and their relationship to sleep. In particular, the temporal and seasonal distribution of cluster headaches and accompanying hormonal changes in migraine, indicate that the circadian system and other sleep and wake generating areas in the hypothalamus may play an important role in their pathophysiology. This article provides a review of the basic neurobiology of circadian rhythms and sleep and its potential implications for understanding the central triggers of some primary headache disorders. The strongest and most direct evidence for a role of the hypothalamus in cluster headache derives from functional brain imaging studies. Furthermore, alteration in the timing and amplitude of hormonal circadian rhythms point to a possible role of the suprachiasmatic nucleus (SCN) in cluster headaches. Improved understanding of the relationship between circadian rhythms, sleep and primary headache disorders is an exciting area of investigation which could lead to innovative circadian and sleep based treatment strategies.