Introduction: Response to indomethacin is an essential feature for the diagnosis of both paroxysmal hemicrania (PH) and hemicrania continua (HC). Cluster headache (CH) is widely considered to be a disease unresponsive to indomethacin.
Case reports: We report four patients with CH who responded to indomethacin. Two patients, who were refractory to the usual therapy for CH, fulfilled the criteria for chronic CH. Conversely, two patients had a history of episodic CH and showed response to both indomethacin and the usual therapy for CH.
Literature review: We also reviewed the literature for the presence of indomethacin response in patients with CH. We noted a large number of cases labeled as CH by the authors which showed a response to indomethacin.
Discussion: Many cases of definite or possible CH were wrongly labeled as PH because of patients' responding to indomethacin.
Conclusion: The response to indomethacin in patients with CH may not be as immediate as in other indomethacin-responsive headaches, and many patients may need larger doses.