Epidemiology and genetics of cluster headache.

Cluster headache, the most severe primary headache, is characterised by unilateral pain, ipsilateral autonomic features, and, in many cases, restlessness. Recent epidemiological studies indicate that the prevalence of cluster headache is about one person per 500. Genetic epidemiological surveys indicate that first-degree relatives are five to 18 times-and second-degree relatives, one to three times-more likely to have cluster headache than the general population. Inheritance is likely to be autosomal dominant with low penetrance in some families, although there may also be autosomal recessive or multifactorial inheritance in others. To date, no molecular genetic clues have been identified for cluster headache. Identification of genes for cluster headache is likely to be difficult because most families reported have few affected members and genetic heterogeneity is likely. Future focus should be on ion channel genes and clock genes. This review summarises the epidemiology and genetics of cluster headache.