—To study nociceptive processing in chronic tension-type headache.
—Survey of the threshold for the nociceptive flexion reflex obtained by sural nerve stimulation in a convenience sample of 40 patients with chronic tension-type headache and in 29 sex- and age-matched healthy subjects. Muscular response was recorded from the biceps femoris muscle. For each stimulation, subjects recorded pain on a visual analogue scale.
—In seven subjects (four headache sufferers and three healthy subjects), no nociceptive flexion reflex response could be elicited. The median nociceptive flexion reflex threshold in the headache group was significantly lower (median, 10 mA) than in the control group (median, 20 mA). Pain tolerance thresholds were significantly lower in the headache group than in the control group. A high degree of correlation was found between nociceptive flexion reflex threshold and tolerated stimulus strength. The slopes of the stimulus intensity/visual analogue scale pain rating response curves were steeper in patients with headache than in control subjects.
—Chronic tension-type headache may represent a disorder of an endogenous antinociceptive system with a lowering of tone and recruitment of descending inhibitory systems.