Adapting Tension-Type Headache to the International Association for the Study of Pain (IASP) Taxonomy: A Conceptual Proposal

Tension-type headache (TTH) is a primary headache characterized by treatment effect heterogeneity, possibly reflecting variations in underlying pain mechanisms. Identifying pain phenotyping or classifying patients into subgroups based on their predominant pain mechanism may provide targeted treatment options. This paper proposes a conceptual adaptation of the International Association for the Study of Pain (IASP) clinical criteria to identify the predominant phenotype in individuals with TTH. It has been found that pain referrals elicited by trigger points (TrPs) reproduce headache symptoms in patients with TTH. Since preliminary studies suggest that TrPs can represent a peripheral nociceptive input, this could lead to considering TTH as a potential nociceptive condition. However, TrP treatment has limited short-term effects for reducing headache frequency, intensity or duration, requiring us to look beyond this possible peripheral driver. Thus, patients with TTH exhibit altered nociceptive processing, which is compatible with nociplastic pain features. Arguably, treatment approaches for nociplastic phenotypes should address maladaptive factors associated with altered nociceptive processing. Based on the current conceptual proposal, TTH should not be viewed as a homogeneous condition but rather as a spectrum in which nociceptive and nociplastic phenotypes coexist with different predominance according to the disease stage and severity. Collectively, it seems that nociceptive and nociplastic mechanisms may contribute to TTH across its clinical spectrum, with nociplastic features appearing to become more prominent in patients with the chronic form of headache. Recognizing the coexistence of nociceptive and nociplastic pain mechanisms may facilitate precision pain management and improve treatment selection in phenotype patients with TTH. In either case, future trials should identify treatment options with long-term effects for TTH, as currently used approaches only yield short-term benefits.