Papers of the Week

Neuroinflammation is implicated in the development and maintenance of persistent pain states, but there is limited data linking cerebrospinal fluid (CSF) inflammatory mediators with neurophysiological pain processes in humans.In a prospective observational study, CSF inflammatory mediators were compared between patients with osteoarthritis (OA) who were undergoing total hip arthroplasty due to disabling pain symptoms (n=52) and pain-free comparison controls (n=30). In OA patients only, detailed clinical examination and quantitative sensory testing were completed. CSF samples were analyzed for ten proinflammatory mediators using Meso Scale Discovery platform.Compared to controls, OA patients had higher CSF levels of interleukin 8 (IL-8) (P=0.002), intercellular adhesion molecule (ICAM) 1 (P=0.007) and vascular cell adhesion molecule (VCAM) 1 (P=0.006). OA patients with central sensitization possibly indicated by arm pressure pain detection threshold (PPDT) <250 kPa showed significantly higher CSF levels of Fms related tyrosine kinase 1 (Flt-1) (P=0.044) and interferon gamma-induced protein 10 (IP-10) (P=0.024), as compared to subjects with PPDT above that threshold. In patients reporting pain numerical rating scale score ≥3/10 during peripheral venous cannulation (PVC), Flt-1 was elevated (P=0.025), and in patients with punctate stimulus wind-up-ratio ≥2, CSF monocyte chemoattractant protein 1 (MCP-1) was higher (P=0.011). Multiple logistic regression models showed that increased Flt-1 was associated with central sensitization, assessed by remote site PPDT and PVC pain, and MCP-1 with temporal summation in the area of maximum pain.Multiple proinflammatory mediators measured in CSF are associated with persistent hip OA-related pain. Pain phenotype may be influenced by specific CSF neuroinflammatory profiles.