Central Pain Modulation and Scalp Tenderness in Frequent Episodic Tension-Type Headache

Objective.- To determine whether the inhibitory effect of acute limb pain on pain to mechanical stimulation of the forehead is compromised in individuals with frequent episodes of tension-type headache. Background.- Central pain modulation processes are disrupted in patients with chronic tension-type headache. This deficit in pain modulation might be a predisposing characteristic that increases vulnerability to tension-type headache and to symptoms such as scalp tenderness, or could be a feature that develops secondarily during attacks and that persists for a few days afterward. To distinguish between these 2 possibilities in the present study, inhibitory pain control was investigated in participants with episodic rather than chronic tension-type headache. Methods.- Pressure-pain thresholds and sensitivity to sharpness in the forehead were measured in 34 individuals with 1-10 episodes of tension-type headache per month and in 32 controls before and after immersion of their hand in painfully cold water. Results.- Before the cold pressor test, pressure-pain thresholds and sensitivity to the sharp stimulus were similar in both groups. Mild headache developed and pressure-pain thresholds in the forehead decreased from 631 +/- 178 g to 579 +/- 196 g (mean +/- SD) after the cold water immersion in the episodic tension-type headache group (P < .05). However, sharpness ratings did not change (mean rating 3.2 +/- 1.4 on a 0-10 scale). In contrast, headache did not develop, pressure-pain thresholds did not change, and sharpness ratings decreased from 3.0 +/- 1.3 to 2.3 +/- 1.1 after the immersion in controls (P < .01). Conclusions.- These findings suggest that endogenous pain modulation processes are compromised in individuals with frequent episodic tension-type headache. This deficit could increase vulnerability to scalp tenderness and recurrent episodes of headache.