Primary and secondary chronic cluster headache: two separate entities?

The International Headache Society (IHS) classification divides chronic cluster headache (CH) into two subtypes: chronic CH unremitting from onset (CCHU) and chronic CH evolved from episodic (CCHE). The purpose of our study was to point out any similarities and differences between the two chronic CH subtypes and to determine whether or not they can be considered as two separate clinical entities. We reviewed data about 31 CCHE patients and 38 CCHU patients referred to the Parma Headache Centre between 1975 and 1999. Clinically, CCHE patients exhibited statistically significant differences from CCHU patients, i.e. earlier CH onset and duration of attacks varying more frequently between 120 and 180 min. From the point of view of lifestyle, heavy alcohol and coffee drinkers prevailed among CCHU patients, while CCHE patients were more frequently heavy smokers. Based on clinical features, it seems reasonable to suppose that chronic CH may occur as two distinct entities.