CPH may be a variation on chronic cluster headache, but this remains unclear. CPH has a female-to-male ratio of 3:1, with a typical onset from age 25 to 35. The pain is usually about the ophthalmic division of the trigeminal nerve, concentrated around the eye, temple, and forehead. However, pain may occur in the occiput or periaural areas. While almost exclusively unilateral, there have been rare instances of bilateral pain. The attacks last from 2 to 45 minutes, with a frequency of 5 to 20 or more per day. The usual attack lasts from 10 to 15 minutes. Occasionally, head movement or mechanical stimulation may precipitate the pain. The pain is associated with at least one of the following: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, ptosis, or eyelid edema. Except for the ptosis, these are mediated by parasympathetic nerves. The pain tends to be be very severe, and is usually stabbing or severely aching. However, at the beginning of the headache, it may be throbbing. There is no clear increase at one particular time of day, and CPH may awaken patients from sleep. In the unusual situation where there is a break of at least a few months (or possibly years), we would term it episodic paroxysmal hemicrania.
CPH is almost always relieved by indomethacin (Indocin). If indomethacin does not help, the diagnosis of CPH is in doubt (although it still could be CPH). Management of Headache and Headache Medications by Lawrence Robbins, M.D. Second Edition 2000