Right-to-left shunt and obstructive sleep apnea in cluster headache

Introduction: Cluster headache (CH) is a trigeminal autonomic cephalalgia characterized by extremely painful, strictly unilateral, headache attacks accompanied by ipsilateral autonomic symptoms. Only few studies investigated a possible role of right-to-left shunt (R-to-LS) and sleep apnea (OSA) in cluster pathogenesis or expression and no prior studies were located that combined the two conditions in CH patients. Objective: To define the potential combined effect of right-to-left shunt and obstructive sleep apnea in patients with cluster headache and their possible influence on the frequency of attacks and on response to oxygen therapy of headache attacks. Methods: 33 patients with cluster headache were recruited and subsequently invited to undergo polysomnography and a transcranial doppler bubble study. Polysomnography is used for the diagnosis of obstructive sleep apnea whereas transcranial doppler bubble study can help diagnose a cardiac right-to-left shunt. Results: Transcranial doppler results demonstrated that 10 out of 31 patients in our cohort had a right-to-left shunt (RLS). Polysomnography revealed that 10 out of 32 patients had obstructive sleep apnea (OSAS). Nineteen out of 33 subjects had one of the two conditions but only one of our 33 patients had both conditions simultaneously. In this sample patients with clear seasonality to their cluster attacks had a higher frequency of obstructive sleep apnea than patients without seasonality. Also a good response to oxygen treatment of the attacks was higher in OSAS patients. Conclusion: the presence of RLS or OSAS, by their possible influence on blood oxygenation, seems to be independently able to predispose to cluster headache or to make it clinically manifest, while the hypothesizable synergistic role between them in favoring cluster headache was not put in evidence. Additionally, our study suggested that the seasonality of cluster headache, may be influenced by the seasonal nature of obstructive sleep apnea. Finally, the presence of sleep breathing alterations seems to be also able to modulate the efficacy of oxygen inhalation on cluster headache attacks.