Compelling evidence has shown chronic widespread and exaggerated pain experience in chronic musculoskeletal pain (MSKP) conditions. In addition, neuroimaging research has revealed both morphological and functional brain alterations in these patients. It is hypothesized that brain alterations play a role in the persistent pain complaints of patients with chronic MSKP. Nevertheless, lack of overview exists regarding the relations between brain alterations and clinical measures of pain.
The present systematic review was performed according to the PRISMA guidelines to investigate the relations between structural or functional brain alterations, utilizing magnetic resonance imaging (MRI) scans, and clinical pain measures in patients with chronic MSKP. PubMed, Web of Science, Cinahl and Cochrane databases were searched. First, the obtained articles were screened on title and abstract. Secondly, the screening was based on full-text. Risk of bias in included studies was investigated based on the modified Newcastle-Ottawa Scale. Twenty studies met the inclusion criteria.
Moderate evidence demonstrates that higher pain intensity and pressure pain sensitivity are related to decreased regional grey matter (GM) volume in brain regions encompassing the cingulate cortex, the insula and the superior frontal and temporal gyrus. Further, some evidence exists that longer disease duration in fibromyalgia is correlated with decreased total GM volume. Yet, inconclusive evidence exists regarding the association of longer disease duration with decreased or increased regional GM volume in other chronic MSKP conditions. Inconclusive evidence was found regarding the direction of the relation of pain intensity and pressure pain sensitivity with microstructural white matter and functional connectivity alterations.
In conclusion, preliminary to moderate evidence demonstrates relations between clinical pain measures, and structural and functional connectivity alterations within brain regions involved in somatosensory, affective and cognitive processing of pain in chronic MSKP.
Nevertheless, inconclusive results exist regarding the direction of these relations. Further research is warranted to unravel whether these brain alterations are positively or negatively correlated to clinical pain measures.