Episodic and Chronic Cluster Headache: Differences in Family History, Traumatic Head Injury, and Chronorisk.

cCH is associated with a positive family history and THI. In familial CH, a peak in nocturnal chronorisk may implicate genes involved in diurnal-, sleep- and homeostatic regulation. The stereotypical nature of the CH attacks themselves is confirmed and differences between subgroups should be sought in other characteristics.