Tension-type headache introduction and diagnostic criteria.

Tension-type headache is the most common primary headache syndrome. Lifetime prevalence ranges from 35% to 80%. There is a distinction between an episodic and a chronic form. This distinction is important, because the chronic subtype strongly implies a neurobiological basis and causes both impairment of quality of life and a high disability score, and is comorbid with anxiety and depressive disorders. The episodic tension-type headache is divided into an infrequent and a frequent subtype. It is known that the frequent type will often be transformed into the chronic type. Tension-type headache often coexists with migraine without aura; therefore both types of headache must be diagnosed separately. Additionally medication overuse headache has to be taken into account when diagnosing tension-type headache. The following chapter reflects the diagnostic criteria for tension-type headache in the context of the revised International Classification of Headache Disorder of the International Headache Society.