title: Prevalence of right-to-left shunts on transcranial Doppler in chronic migraine and medication-overuse headache.
abstract: BACKGROUND
  It was suggested that right-to-left shunt (RLS) may be highly prevalent in chronic migraine (CM) patients, indicating that patent foramen ovale (PFO) might be an aggravating and chronifying factor of migraine. Since a high proportion of chronic migraineurs also have medication-overuse headache (MOH), one may wonder if they have a more severe form of the disorder and more frequently a PFO.
  
  
  OBJECTIVE
  The objective of this study is to determine the prevalence and grade of RLS in patients suffering from CM and MOH.
  
  
  METHODS
  A cross-sectional multicenter study of air-contrast transcranial Doppler was conducted in 159 patients with CM ( N  = 57) or MOH ( N  = 102) attending a tertiary headache clinic.
  
  
  RESULTS
  The prevalence of RLS in CM was 37% (11% large shunts) and in MOH patients 31% (13% large shunts). There was no difference between the two groups ( P  = 0.49).
  
  
  CONCLUSIONS
  RLS prevalence in CM is within the upper range of those reported in episodic migraine without aura or in the general population, and not higher in MOH. PFO is thus unlikely to have a significant causal role in these chronic headaches.
authors.affiliation: Danish Headache Center and Department of Neurology, Glostrup Hospital, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Song
authors.initials: S
authors.lastname: Guo
authors.forename: Sarvnaz
authors.initials: S
authors.lastname: Shalchian
authors.forename: Pascale
authors.initials: P
authors.lastname: Gérard
authors.forename: Michael
authors.initials: M
authors.lastname: Küper
authors.forename: Zaza
authors.initials: Z
authors.lastname: Katsarava
authors.forename: Messoud
authors.initials: M
authors.lastname: Ashina
authors.forename: Jean
authors.initials: J
authors.lastname: Schoenen
mesh_terms: D000328:Adult; D002908:Chronic Disease; D015897:Comorbidity; D005060:Europe / Q000453:epidemiology; D005260:Female; D054092:Foramen Ovale, Patent / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D051271:Headache Disorders, Secondary / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017585:Ultrasonography, Doppler, Transcranial / Q000706:statistics & numerical data*
keywords: Chronic migraine; medication-overuse headache; migraine; patent foramen ovale; right-to-left shunt; transcranial Doppler