These are based on the frequency and duration of attacks. Regarding frequency, less than 15 days a month is episodic, greater than 15 days chronic. Regarding duration, less than 4 hours is short and greater than 4 hours long.
- Episodic short-duration headaches: Trigeminal autonomic cephalgias, such as cluster, SUNCT, SUNA, hypnic headache, stabbing headaches.
- Episodic long-duration headaches: Migraine and tension-type headache.
- Chronic short-duration headaches: Chronic cluster and chronic paroxysmal hemicrania.
- Chronic long-duration headaches: Chronic migraine, chronic tension-type headache, new daily persistent headache, hemicrania continua. If a headache in this group is unilateral, a trial of indomethacin is indicated, and if effective, the patient has hemicrania continua.