Headache temporal patterns: towards a chronobiological model.

Rhythmical changes in terrain susceptibility and trigger occurrence can induce periodic temporal patterns in headache patients, with readily foreseeable frequency cycles of attacks. The impaired ability of biological functions to adjust to cyclic environmental changes represents the minus, the handicap, the increased risk of clinical symptomatology (headache); attacks occur when the precarious systems of these patients are forced by cyclical environmental stimuli towards phase shiftings or to cope with new levels of performance. A dyschronic hypothesis of primary headache must be based upon observations demonstrating that along with dysfunctions of the pain control systems there is also a vulnerability of the rhythmic physiological organization of CNS.