IntroductionCluster headache is an uncommon, highly debilitating primary headache, characterized by brief, severe, unilateral headaches, accompanied by homolateral eye reddening, lacrimation, rhinorrhea, ptosis, etc. [1]. These attacks occur in cluster periods lasting weeks or months. The etiology and pathogenesis of this headache have not been clearly established. Until fairly recently, the disease was considered to be sporadic. However, a family history of cluster headache is reported in 2%-7% of patients [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Furthermore, the condition was described in both members of five pairs of monozygotic twins [16][17][18] and in three generations of a single family [19][20][21]. A Danish study [15] on cluster headache patients attending neurological clinics in Arhus, east-central Jutland, and Copenhaghen County, found that 7% (25 of 366) of patients had a family history of cluster headache, with 25 first-degree relatives and six second-degree relatives affected. The relative risk for the illness was 14-and 2-times greater, respectively, in first-and second-degree relatives of patients with cluster headache than in the general population. These findings constitute strong prima facie evidence that cluster headache has a heritable component in at least a fraction of patients. We designed a study to uncover evidence that genetic factors play a role in the genesis of cluster headache in an Italian population of cluster headache patients. To this aim, we assessed the relative risk of cluster headache in first-and second-degree relatives of cluster headache patients attending our headache center in Milan.
Materials and methodsWe studied 191 patients (118 males, 73 females, average age 45.9 years) attending the Headache Center of the C. Besta National Neurological Institute, Milan. All patients (probands) were of J Headache Pain (2000) 1:S165-S167 © Springer-Verlag 2000 A study of Italian families with cluster headache