Complex regional pain syndrome (CRPS) is a debilitating chronic pain condition. Recent brain imaging studies have highlighted the role of cortico-striatal brain circuitry in pain chronification; however, the role of this circuitry in the persistence of CRPS pain has not been studied yet. Here, we investigated whether frequently reported changes in the cortico-striatal brain circuitry in chronic pain extend also to chronic CRPS. CRPS patients were recruited as part of a research study on chronic pain. Quantitative sensory testing and resting-state functional brain activity data were compared between 22 patients with acute CRPS (aCRPS, pain duration, 12 months). Patients with cCRPS reported decreased sensitivity to pressure pain compared with aCRPS patients. In parallel, resting-state brain activity power within the slow-5 low-frequency band (0.01-0.027 Hz) in the nucleus accumbens-a brain functional signature identified in chronic low-back pain patients-was decreased in cCRPS patients and effectively discriminated acute from chronic CRPS patients, with an area under the curve (AUC) of 0.79. Although cortico-striatal connectivity did not differ between the groups, exploratory whole-brain comparisons revealed stronger connectivities in the aCRPS patients centered mainly on the precuneus/posterior cingulate of the default mode network and the frontal operculum/mid-insula of the ventral attention/salience network. These findings show that cCRPS patients share neuroplasticity in the accumbens with other chronic pain patients and suggest a major shift in functional connectivities affecting networks involved in nociceptive and self-referential processing between aCRPS and cCRPS. Trial Registration: https://drks.de/ - registration number DRKS00016790.
Chen et al. (Fri,) studied this question.