Cerebrospinal fluid hypocretin-1 levels during the active period of cluster headache

Background: Hypocretins (orexins) are hypothalamic neuropeptides which are involved in a wide range of physiological processes in mammals including central pain processing. Genetic studies in humans evidenced a role for the hypocretinergic system in cluster headache (CH). Patients and methods: We tested cerebrospinal fluid (CSF) hypocretin-1 (orexin-A) levels in 10 CH patients during an active cluster period. CSF hypocretin-1 levels were measured by radioimmunoassay. Results: CSF hypocretin-1 levels were within the normal range (mean 457.3 +/- 104.98 pg/ml, range 304-639) in our 10 patients, with a slight reduction in one case (304 pg/ml). There were no associations between CSF hypocretin-1 levels and the clinical features of CH. A trend towards higher hypocretin-1 levels was disclosed in patients with chronic CH compared to episodic CH. Conclusions: CSF hypocretin-1 levels seem not to influence the clinical course of CH, but our results cannot completely exclude a functional involvement of the hypothalamic hypocretinergic system in the pathogenesis of CH.