Elevated cytokine levels in the central nervous system of cluster headache patients in bout and in remission.

Background: Cluster headache is characterized by activation of the trigeminovascular pathway with subsequent pain signalling in the meningeal vessels, and inflammation has been suggested to play a role in the pathophysiology. To further investigate inflammation in cluster headache, inflammatory markers were analysed in patients with cluster headache and controls.

Methods: We performed a case-control study, collecting cerebrospinal fluid and serum samples from healthy controls, cluster headache patients in remission, active bout, and during an attack to cover the dynamic range of the cluster headache phenotype. Inflammatory markers were quantified using Target 48 OLINK cytokine panels.

Results: Altered levels of several cytokines were found in patients with cluster headache compared to controls. CCL8, CCL13, CCL11, CXCL10, CXCL11, HGF, MMP1, TNFSF10 and TNFSF12 levels in cerebrospinal fluid were comparable in active bout and remission, though significantly higher than in controls. In serum samples, CCL11 and CXCL11 displayed decreased levels in patients. Only one cytokine, IL-13 was differentially expressed in serum during attacks.

Conclusion and interpretation: Our data shows signs of possible neuroinflammation occurring in biological samples from cluster headache patients. Increased cerebrospinal fluid cytokine levels are detectable in active bout and during remission, indicating neuroinflammation could be considered a marker for cluster headache and is unrelated to the different phases of the disorder.