Prevalence of right-to-left shunts on transcranial Doppler in chronic migraine and medication-overuse headache.

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.