Prevalence of right-to-left shunt in patients with cluster headache.

Recent investigations documented that the prevalence of right-to-left shunt (RLS) in patients with migraine with aura (MA) is significantly higher than in healthy controls and similar to prevalence of RLS in young patients with cryptogenic stroke (CS). Nevertheless, little data are available in the literature about RLS prevalence in the other forms of primary headache. The aim of this study was to investigate the occurrence of RLS in patients with cluster headache (CH). We enrolled 30 consecutive patients with CH diagnosis according to the IHS criteria and 40 controls. RLS was assessed with bilateral transcranial Doppler contrast (TCDc) monitoring of middle cerebral arteries. Eleven patients (37%) resulted positive to TCDc monitoring for evaluation of RLS. These data show that the presence of RLS in this group is more prevalent than in the general population and similar to that found in MA and in CS.