Understanding pathophysiology of cluster headache: Heart rate variability and parasympathetic activation

Aim: The underlying mechanisms of cluster headache (CH) have not been fully understood yet. The cranial autonomic activation suggests that both sympathetic and parasympathetic systems are impaired in the clinical presentation; however, the systemic autonomic involvement during pain-free episodes is not well-known. Methods: Thirty-five subjects were included in 24 h Holter monitoring and electrophysiological studies in this controlled study. Results: In Holter monitoring, heart rate variability parameters, RMSSD (P = 0.001), and pNN50 (P = 0.024) were significantly higher in patients compared to age and gender-matched controls. The R-R variations during breathing and deep breathing and sympathetic skin responses of all patients were normal. Conclusions: High RMSSD and pNN50 levels are the two indicators of increased parasympathetic activity in CH patients. Considering the intense stress because of severe pain of the CH patients, who are mostly adult men and smokers, there is an urgent need for broader studies with prospective follow-up in terms of cardiac health.