Mechanisms of spontaneous tension-type headaches: an analysis of tenderness, pain thresholds and EMG.

Pericranial muscle tenderness, EMG levels and thermal and mechanical pain thresholds were studied in 28 patients with tension-type headache and in 30 healthy controls. Each patient was studied during as well as outside a spontaneous episode of tension-type headache. Outside of headache, muscle tenderness and EMG levels were significantly increased compared to values in controls subjects, while mechanical and thermal pain thresholds were largely normal. During headache, muscle tenderness evaluated by blinded manual palpation increased significantly, while pressure pain thresholds remained normal and pressure pain tolerances decreased. Thermal pain detection and tolerance threshold decreased significantly in the temporal region, but remained normal in the hand. EMG levels were unchanged during headache. It is concluded that one of the primary sources of pain in tension-type headache may be a local and reversible sensitization of nociceptors in the pericranial muscles. In addition, a segmental central sensitization may contribute to the pain in frequent sufferers of tension-type headache.