Central and peripheral mechanisms in chronic tension-type headache

The second exteroceptive suppression of masseter muscle activity (ES2) and tenderness in pericranial muscles were evaluated in 112 young adults who met IHS criteria in the following diagnostic classifications: 31 chronic tension headache, 31 episodic tension headache, 33 migraine without aura and 17 migraine with aura. An additional 31 subjects served as controls. Pericranial muscle tenderness better distinguished diagnostic subgroups and better distinguished recurrent headache sufferers from controls than did masseter ES2. Chronic tension headache sufferers exhibited the highest pericranial muscle tenderness, and controls exhibited the lowest tenderness (P < 0.01). All chronic tension headache sufferers exhibited muscle tenderness in at least one of the pericranial muscles evaluated, while tenderness was exhibited by 52% of controls. The association between pericranial muscle tenderness and chronic tension headache was independent of the intensity, frequency, or chronicity of headaches. Our findings raise the possibility that pericranial muscle tenderness is present early in the development of tension headache, while ES2 suppression only emerges later in the evolution of the disorder.