Familial aggregation of cluster headache.

Several studies suggest a strong familial aggregation for cluster headache (CH), but so far none of them have included subjects with probable cluster headache (PCH) in accordance with the International Classification of Headache Disorders. Objective: To identify cases of probable cluster headache and to assess the-familial aggregation of cluster headache by including these subjects. Method: Thirty-six patients attending a headache consultation and diagnosed with trigeminal autonomic headaches were subjected to a questionnaire-based interview. A telephone interview was also applied to all the relatives who were pointed out as possibly affected as well as to some of the remaining relatives. Results: Twenty-four probands fulfilled the criteria for CH or PCH; they had 142 first-degree relatives, of whom five were found to have CH or PCH, including one case of CH sine headache. The risk for first-degree relatives was observed to be increased by 35- to 46-fold. Conclusion: Our results suggest a familial aggregation of cluster headache in the Portuguese population.