Background: In addition to debilitating fatigue the majority of patients with chronic fatigue syndrome (CFS) experience chronic widespread pain.
Aims: Conducting a systematic review to critically assess the existing knowledge on chronic pain in CFS. We focussed on the definition, the prevalence and incidence, the aetiology, the relevance and the therapy strategy for chronic musculoskeletal pain and post-exertional pain in CFS.
Methods: To identify relevant articles, we searched eight medical search engines. The search terms "chronic fatigue syndrome" AND "pain", "nociception", "arthralgia" and "myalgia", were used to identify articles concerning pain in CFS. Included articles were reviewed by two blinded researchers.
Results: Twenty-five articles and two abstract were identified and selected for further appraisal. Only 11 search results focussed on musculoskeletal pain in CFS patients. Regarding the standardized review of the articles, a 96% agreement between the researchers was observed. There is no consensus in defining chronic widespread pain in CFS, and although there is little or no strong proof for the exact prevalence, chronic pain is strongly disabling in CFS. Aetiological theories are proposed (sleep abnormalities, tryptophan, parovirus-B, hormonal and brain abnormalities and central sensitisation) and a reduction of pain threshold after exercise has been shown. Furthermore depression seemed not related to pain in CFS and a staphylococcus toxoid vaccine caused no significant pain reduction.
Conclusions: The results from the systematic review highlight the clinical importance of chronic pain in CFS, but only few studies addressing the aetiology or treatment of chronic pain in CFS are currently available.