This type of headache is classified as a trigeminal autonomic cephalalgia (TAC). There are 4 types of TACs, and hemicrania continua is one of them. Hemicrania continua is a continuous one-sided headache (side-locked, does not alternate sides) of at least 3 months duration with moderate to severe exacerbations. There should be either agitation or restlessness and/or at least 1 autonomic sign or symptom on the side of the headache [lacrimation (runniness/tearing of the eye), conjunctival injection (redness of the eye), facial sweating or flushing (skin turning blushed), nasal congestion, rhinorrhea (runniness of nose), sense of ear fullness, eyelid edema (swelling), or partial Horner’s syndrome (miosis (pupil becomes small)) and/or ptosis (droopiness of the eye)]. Although not included in the criteria, sometimes patients describe a sensation such as something irritating in the eye on the side of the headache, such as sand, grit, or a hair, but nothing is found.
To make the full diagnosis, the patient must respond completely to a therapeutic trial of indomethacin (a specific anti-inflammatory (NSAID) medication), used in a very specific way (“Indomethacin trial”). For this reason, this headache is 1 of 2 types of “Indomethacin-sensitive” headaches because Indomethacin is typically the only thing that works. The diagnosis of hemicrania continua is confirmed by the headache completely stopping after reaching a specific dose of Indomethacin.