Circulating microRNA signatures associated with response to lumbar sympathetic ganglion block in complex regional pain syndrome: an exploratory pilot study

Lumbar sympathetic ganglion block (LSGB) is used for lower limb complex regional pain syndrome (CRPS), yet reliable biomarkers for predicting treatment response are lacking. This study evaluated the association between circulating microRNAs (miRNAs) and clinical outcomes after LSGB. Twenty patients with CRPS were enrolled, and plasma samples were obtained at baseline (T0), 1 week (T1), and 3 weeks (T2). Responders ( n = 10) were defined as a ≥ 30% reduction in Numeric Rating Scale pain scores at T1. During the screening phase, 12 randomly selected patients underwent a 768-target quantitative polymerase chain reaction array, from which several candidate miRNAs were identified. Seven genes of interest and four reference genes were selected for the validation. In the validation cohort, responders demonstrated significantly higher baseline levels of miR-21-5p, whereas miR-625-5p showed a non-significant upward trend. Longitudinal profiling revealed no significant temporal changes in either miRNA among responders, whereas both increased significantly in non-responders. In this exploratory pilot study, higher baseline levels of miR-21-5p in responders were associated with a favorable clinical response to LSGB, while the subsequent divergent longitudinal trajectories of miR-21-5p and miR-625-5p suggest biological differences potentially related to treatment resistance. These preliminary findings support further investigation of circulating miRNAs as candidate biomarkers of treatment response in CRPS and warrant validation in larger, adequately powered cohorts.