Chapter 33 - Pathophysiology of cluster headache and other trigeminal autonomic cephalalgias

Abstract

This chapter discusses pathophysiological mechanisms in cluster headache (CH). CH has been recognized for many years, whereas short-lasting unilateral neuralgiform pain with conjunctival injection and tearing (SUNCT) and the paroxysmal hemicranias (PH) are rare headache syndromes that is described in the chapter. Consequently, there are far more studies regarding CH than SUNCT and PH. Typically CH attacks are strictly unilateral, with the maximal pain localized deep behind one eye or the temple, and associated with ipsilateral facial autonomic symptoms. Mapping of the trigeminovascular system and the trigeminoautonomic reflex has provided a new basis for the understanding of the trigeminal autonomic cephalalgias (TACs). The ipsilateral facial autonomic symptoms associated with the cluster attack suggest both sympathetic deficit and parasympathetic hyperactivity. Several sources of the autonomic symptoms are presently under consideration at central as well as peripheral levels. The episodic nature of CH, in particular the timing of single attacks and periods, circadian neurendocrine disturbances and systemic effects such as altered lipolysis, is likely to be related to hypothalamic dysfunction. Recurrent activation of the trigeminovascular system with parasympathetic recruitment and vasodilation explains many of the clinical features of CH but the trigger of this activation is unknown. Possibly attacks may be initiated by hypothalamic discharge. The local sympathoplegia, overt or subclinical, most probably is of peripheral origin and not a cause of the pain, but once the attack begins these autonomic disturbances may contribute to the rapid escalation of pain.