Misdiagnosis of cluster headache.

Misdiagnosis of cluster headache is common in clinical practice and can lead to significant morbidity. The International Headache Society has published diagnostic criteria that are generally straightforward and useful, but careful understanding of these criteria and how to handle exceptions is necessary. The primary diagnostic points involve severity, length, and frequency of individual headache attacks, as well as the presence of ipsilateral autonomic features. Such additional features as time cycling of headache clusters, physical characteristics of patients, and response to treatment may prove useful in individual cases, but must not be relied on too much.