ORIGINAL ARTICLE Transcranial Doppler study in patients with cluster head

allowed to calculate the breath holding index. Results: The breath holding index following administration of oxygen (BHI-O2) was higher in the Conclusion: Cerebral vessels are more reactive to stimuli after O2 inhalation in patients with cluster headache. Cerebrovascular reactivity may be one of the future predictors of good response to O Hemodynamic changes in cluster headache (CH) have received less attention compared with the entity of signs/symptoms of the disease. Administration of oxygen during the CH attack has been demonstrated to reduce/interrupt the pain in 70% of the patients.1,2 Few studies have focused on cerebral blood flow (CBF) during the different phases of CH (active/remis-sion), and the effect of oxygen therapy on it. Recently, transcranial Doppler (TCD) monitoring of cerebral blood velocity (CBV) at the middle cerebral arter