The superior pericarotid cavernous sinus plexus and cluster headaches

Little is known about the aetiology or pathology of cluster headaches, and even less is known about its possible anatomical origins. In the complete form of a cluster headache, patients experience pain referred to by the first and second division of the trigeminal nerve, ocular sympathetic dysfunction (Homer's syndrome), forehead and facial sweating due to the stimulation of superior cervical ganglia projections, and parasympathetic activation which manifests as lachrymation, conjunctival injection, nasal congestion, and rhinorrhoea. Some severely affected patients are successfully treated with chemical- or heat-induced trigeminal lesions, whereas others benefit from the injection of local anaesthetics into the sphenopalatine fossa or from the removal of the sphenopalatine ganglion. It is believed that if a single 'lesion' does exist to explain all these symptoms and treatments, it must be small, and must reside within a remote region of the nervous system to escape detection by presently available diagnostic techniques. Recent anatomical data in primates suggest that such a disturbance may be localized to the superior aspect of the pericarotid cavernous sinus plexus.