Cluster headache. Ultrastructural aspects and pathogenetic mechanisms.

The skin of both temples was examined ultrastructurally in six patients with cluster headaches and in three controls. An increased number of mast cells were present in the patients irrespective of whether they were in a cluster period or in a quiescent phase. The mast cells were found perivascularly and in the vicinity of cutaneous nerves in the patients, whereas they were predominantly found in perivascular areas in controls. Mast cell degranulation was not more prominent on the side of the pain and occasional degranulated mast cells were found in controls. These findings are consistent with the hypothesis that cluster headache is due to an axonal reflex in the trigeminal system, initiated perhaps by latent viral infection of IgE activation of mast cells.