Potential Contribution of Hypertension to Evolution of Chronic Migraine and Related Mechanisms

Aims: To investigate the potential contributions of diastolic and systolic blood pressure (BP) and the circadian rhythm of BP to chronic migraine evolution. Methods: This cross-sectional study included four groups of patients selected based on migraine frequency (high frequency ≥ 10 days per month and low frequency < 10) and on the presence of hypertension. Among-group and pairwise comparisons were carried out to investigate potential neurophysiologic differences in the cerebral vessel reactivity to a nitroglycerin test, in autonomic balance (tilting test), and BP circadian rhythm. Results: A more marked decrease in cerebral blood flow velocity was observed in hypertensive high-frequency migraineurs compared to all other groups (P = .037). Moreover, a smaller decrease in vagal tone was recorded in the orthostatic position in hypertensive subjects, whether they were high- (P = .032) or low-frequency migraineurs (P = .014), with a consistently higher vagal to sympathetic tone ratio (P = .033). Finally, in nonhypertensive subjects, a higher but not significant prevalence of systolic nondippers was detected in high-frequency migraineurs (67%) compared to low-frequency subjects (25%; P = .099). Conclusion: These findings suggest that hypertension may contribute to the chronic evolution of headache with mechanisms shared with migraine; ie, vascular tone alteration and autonomic dysregulation.