Chronic tension-type headache.

Tension-type headache is the most common headache type worldwide. Chronic tension-type headache (CTTH) affects 2% to 3% of patients, yet it represents the least talked about subtype of chronic daily headache. There is much debate in the headache community on whether CTTH exists as its own entity or is a milder form of chronic migraine (CM), because there are similarities and differences between the two headache forms. This article reviews CTTH, as well as the current pathophysiology and treatment, and discusses controversial issues in the diagnosis of CTTH and CM.