Plasma pro-inflammatory markers in chronic neuropathic pain: A multivariate, comparative, cross-sectional pilot study

Abstract

Abstract Background Caused by a lesion or disease of the somatosensory system, neuropathic pain is notoriously difficult to treat with conventional analgesics. It has been suggested that inflammatory cytokines play a role in the development and maintenance of neuropathic pain. But human studies of these substances are relatively few and partly contradictory. Objectives To simultaneously investigate the plasma levels of chemokine interleukin 8 (IL-8) and the cytokines IL-6, IL-1 β, and Granulocyte macrophage colony-stimulating factor (GM-CSF) in patients with peripheral neuropathic pain (most of whom due to failed back surgery syndrome) (n = 14) compared to controls (n = 17). Results IL-6 was significantly higher in patients than in controls (0.92 ± 0.12 pg/ml vs. 0.57 ± 0.08 pg/ml, p = 0.012). IL-1 ß, IL-8, and GM-CSF levels did not differ between the two groups. A multivariate analysis showed a tendency for patients also to have higher GM-CSF plasma levels than controls. Conclusions This study found an increased level of IL-6 in plasma in patients with neuropathic pain, but not for the other pro-inflammatory substances investigated. There are several possible confounders not registered or controlled for in this and other studies of neuropathic pain. Implications Larger studies that take several possible confounders into consideration are needed to further investigate the levels of plasma cytokines in different pain conditions.