Chronic short-lasting headaches: clinical features and differential diagnosis.

Chronic short-lasting headaches are relatively rare, poorly recognized syndromes. The chronic short-lasting headaches are a group of chronic disorders in which the headaches occur for one year or more, either without remission or with remission periods less than two weeks; each attack lasts less than 4 hours. These headache syndromes are divided into those with autonomic activation and those without autonomic activation. This article presents the clinical features and differential diagnosis of the relatively rare and clinically challenging trigeminal autonomic cephalgias (TACs). The article also focuses on the clinical features and differential diagnosis of hypnic headache, a chronic shortlasting, non-unilateral headache of moderate intensity in which there is no autonomic involvement, in order to differentiate this from chronic cluster headache, with which it is often confused.