Eighty to ninety percent of cluster headache patients have pain over a number of days to a whole year.

VOA: special.2010.03.30

The Cleveland Clinic in Ohio says the cluster headache can be many times more intense than a migraine.

VOA: special.2010.03.30

Cluster headaches occur in cycles: sufferers can experience several headaches a day for weeks or even months on end.

VOA: standard.2009.12.17

"Our study showed for the first time a clear difference between oxygen and air in the treatment of acute cluster headache.

VOA: standard.2009.12.17