Noxious Inhibition of Temporal Summation is Impaired in Chronic Tension-Type Headache

Objective.- To examine effects of stress on noxious inhibition and temporal summation (TS) in tension-type headache. Background.- Stress is the most commonly reported trigger of a chronic tension-type headache (CTH) episode; however, the mechanisms underlying this are unclear. Stress affects pain processing throughout the central nervous system, including, potentially, mechanisms of TS and diffuse noxious inhibitory controls (DNIC), both of which may be abnormal in CTH sufferers (CTH-S). No studies have examined TS of pressure pain or DNIC of TS in CTH-S to date. Similarly, effects of stress on TS or DNIC of TS have not been reported in healthy subjects or CTH-S to date. Methods.- The present study measured TS and DNIC of TS in CTH-S and healthy controls (CNT) exposed to an hour-long stressful mental task, and in CTH-S exposed to an hour-long neutral condition. TS was elicited at finger and shoulder via 10 pulses from a pressure algometer, applied before and during stimulation from an occlusion cuff at painful intensity. Results.- Algometer pain ratings increased more in the CTH compared with the CNT group, and were inhibited during occlusion cuff more in the CNT compared with CTH groups. Task effects on TS or DNIC were not significant. Conclusions.- The results indicate increased TS to pressure pain and impaired DNIC of TS in CTH-S. Stress does not appear to aggravate abnormal TS or DNIC mechanisms in CTH-S.