title: A Review of Cardiovascular Autonomic Control in Cluster Headache.
abstract: OBJECTIVE
  This review aims to evaluate existing literature concerning cardiovascular autonomic function and CH. Suggestions about future research are offered and known difficulties in investigating the autonomic nervous system in cluster headache are discussed.
  
  
  BACKGROUND
  Little is known of the pathophysiological mechanisms behind cluster headache. Cranial autonomic features are an inherent and diagnostic feature; however, a number of studies and clinical observations support the involvement of systemic autonomic control in its pathophysiology. Further, cluster headache attacks are apparently more easily triggered during periods of parasympathetic dominance. A better understanding of this interaction may provide insight into central autonomic regulation and its role in cluster headache.
  
  
  METHODS
  A PubMed search was performed in April 2015 using the search terms "cluster headache," "cardiovascular," "autonomic nervous system," and "cardiac." References of identified articles were also searched for relevant articles. Studies were included if they contained data on cardiovascular or autonomic responses to autonomic tests, induced or spontaneous attacks.
  
  
  RESULTS
  In total, 22 studies investigating cardiac autonomic control in cluster headache were identified. Three overall categories of investigations exist: (1) Those studying changes in heart rate, blood pressure, and electrocardiographic changes; (2) those employing various clinical autonomic tests; and finally (3) those using spectral and nonlinear analysis of heart rate variability. Although not completely congruent, overall, results suggest ictal hyperactivation of the parasympathetic branch and a sympathetic deficit. Subclinical autonomic dysregulation is also present in the pain-free state.
  
  
  CONCLUSIONS
  Cardiac autonomic control is subclinically affected in cluster headache. The changes could be attributed to the suggested central dysregulation present in this disorder.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Bispebjerg and Frederiksberg Hospital, University of Copenhagen, Denmark.|Danish Headache Center, Glostrup Hospital, Denmark.
authors.forename: Mads C J
authors.initials: MC
authors.lastname: Barloese
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology*; D001794:Blood Pressure / Q000502:physiology; D003027:Cluster Headache / Q000175:diagnosis* / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D039781:PubMed / Q000706:statistics & numerical data
keywords: autonomic dysfunction; autonomic nervous system; cluster headache; hypothalamus; pain