Hemicrania continua and symptomatic medication overuse.

Hemicrania continua (HC) is a rare, strictly unilateral, nonparoxysmal headache disorder characterized by its absolute responsiveness to indomethacin. The pain is usually moderate in intensity and frequently associated with a superimposed "jabs and jolts" headache. We report two cases of HC which presented as chronic daily headache (CDH) with abortive medication overuse. CDH can be due to transformed migraine (TM), new daily persistent headache (NDPH), chronic tension-type headache, and HC. All can be unilateral, and all can be associated with medication overuse. Our two cases meet the criteria for HC based on indomethacin responsiveness. One meets the criteria for TM, the other NDPH. Is HC a distinct disorder, or a subset of these other disorders? CDH with medication overuse includes in its differential diagnosis HC.