Two cases of symptomatic cluster-like headache suggest the importance of sympathetic/parasympathetic balance.

Despite several reports on symptomatic cluster-like headache, there is no clear explanation of how different lesions thought to be causative are related to cluster-like headache. On the basis of two additional cases of symptomatic cluster headache, we discuss the possibility that an acute imbalance of the autonomic nervous system, namely a net overactivity of the parasympathetic system, may be able to trigger these headache attacks in patients who probably have an additional individual predisposition to react with a cluster-like headache. Such an imbalance can be due to an increase in parasympathetic tone (e.g. stimulation of parasympathetic fibres) or to a reduction of the sympathetic tone (e.g. a lesion of the sympathetic fibres).