Mechanical allodynia and hyperalgesia in nerve and muscles in chronic tension-type headache

Abstract

Evidence suggests that the most prominent finding in chronic tension-type headache (CTTH) is an increased tenderness to palpation of pericranial muscle tissues. Furthermore, lowered pain detection and tolerance thresholds found in CTTH suggest both allodynic and hyperalgesic response to pressure stimulation. Nevertheless, whether this mechanical hypersensitivity is a primary or a secondary phenomenon to CTTH is not clear. One recent study has demonstrated that pain sensitivity is a consequence not a causative factor of CTTH. Additionally, nerve tissues have also been found to be sensitized in CTTH. Recent evidence is modifying previous knowledge about relationships between muscle tissues and CTTH, since it has been found that trigger points, but not tender points, are responsible for peripheral nociceptive inputs in CTTH. An updated pain model suggests that headache perception can be explained by referred pain from active trigger points in the craniocervical muscles, mediated through the spinal cord and the trigeminal nucleus caudalis rather than only tenderness (tender points) of the muscles themselves.