Resting-State Brain Activity in Acute and Chronic Complex Regional Pain Syndrome.

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) and 20 with chronic CRPS (cCRPS, 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.