Response to 100 %
oxygen as acute treatment for
cluster headache is relative low considering certain subgroups or predictors. The primary purpose of the present study was to find prospectively which factors differ between responders and non-responders to
oxygen therapy. The second goal was to find whether any of these differences would clarify the mechanism of
pain reduction by
oxygen and
cluster headache pathophysiology. Patients diagnosed with
cluster headache according to the ICHD-II criteria, who started on
oxygen therapy (n = 193), were recruited from 51 outpatient clinics and via patient websites in The Netherlands. Patients had to return two questionnaires around the start of
oxygen therapy (n = 120). Eventually, 94 patients were included. Clear non- plus moderate responders had ever used
pizotifen more often (p = 0.03). Clear non-responders more often had
photophobia or
phonophobia during
cluster headache attacks (p = 0.047) and more often had used
triptans in the same active phase as the phase in which they had used
oxygen for the first time (p = 0.02). Using correction for multiple testing, we could only confirm a statistically significant difference in
triptan use. We were unable to locate the level of action of
oxygen in the thalamus and cortex or confirm the sites of its action presently known, solely based on current knowledge of
photophobia circuits. However, we conclude that particularly the higher frequency of
photophobia or
phonophobia in clear non-responders deserves further study to understand the mechanism of
pain reduction by
oxygen and
cluster headache pathophysiology.