Quantitative somatosensory testing of subjects with chronic post-traumatic headache: Implications on its mechanisms

Background: Chronic headache is one of the most prominent symptoms among subjects with traumatic head injury (THI). Despite the relatively high prevalence of chronic post-traumatic headache (CPTHA) and its enormous effect on the already poor quality of life of subjects with THI, its mechanisms has not been studied in depth. Objective: To conducted quantitative somatosensory testing in THI subjects with and without chronic post-traumatic headache (CPTHA) in order to shed light on the yet, unknown pathophysiology of CPTHA. Methods: THI subjects with and without CPTHA and healthy controls underwent thermal and mechanical threshold measurements in painful and pain-free regions in the head and in their hands (a remote pain-free region) and filled out and the post-traumatic stress disorder (PTSD) inventory. In addition, the THI and CPTHA filled out the Mc'Gill pain questionnaire (MPQ). Results: THI subjects with CPTHA had significantly higher thermal thresholds in both the head and hand indicating central damage to the pain and temperature system and in addition, a significantly lower pressure-pain threshold in the head as well as more severe PTSD symptomatology than the pain-free THI subjects and healthy controls. Conclusions: The sensory profile of subjects with CPTHA suggests that CPTHA may be a form of central pain. The cranial mechanical hyperalgesia may originate from peripheral tissue damage accompanying the THI. Psychological factors may contribute to the development, and maintenance of CPTHA in susceptible individuals.