Classification of Cluster Headache

sumatriptan or DHE mesylate provide significant relief for about 80 percent
of patients. An intranasal local anesthetic may provide relief for some
patients.
Classification of Cluster Headache
According to its duration, the International Headache Society (IHS)
classifies CH into episodic and chronic.
Episodic CH occurs in periods (clusters) lasting in duration from 7 days to
1 year, but separated by pain-free intervals lasting at least 2 weeks in
duration. Typically, a cluster lasts 2 weeks to 3 months.
Chronic Cluster Headache
Chronic Cluster headache is defined as that occurring for more than 1 year
without remission or without remissions lasting less than 2 weeks. It is
subdivided into chronic CH from onset and chronic CH evolving from
episodic. Chronic CH is notoriously difficult to treat and resistant to
standard prophylactic agents.