LAUSR

OBJECTIVE Widespread pain hypersensitivity and enhanced temporal summation of pain (TSP) are commonly reported in patients with complex regional pain syndrome (CRPS) and discussed as proxies for central sensitization. This study aimed to directly relate such signs of neuronal hyperexcitability to the pain phenotype of CRPS patients. METHODS Twenty-one CRPS patients and 20 healthy controls (HC) were recruited. The pain phenotype including spatial pain extent (assessed in % body surface) and intensity were assessed and related to widespread pain hypersensitivity, TSP, and psychological factors. Quantitative sensory testing (QST) was performed in the affected, the contralateral and a remote (control) area. RESULTS CRPS patients showed decreased pressure pain thresholds in all tested areas (affected: t(34)=4.98, p < 0.001, contralateral: t(35)=3.19, p = 0.005, control: t(31)=2.65, p = 0.012). Additionally, patients showed increased TSP in the affected area (F(3,111)=4.57, p = 0.009) compared to HC. TSP was even more enhanced in patients with a high compared to a low spatial pain extent (F(3,51)=5.67, p = 0.008), suggesting pronounced spinal sensitization in patients with extended pain patterns. Furthermore, the spatial pain extent positively correlated with the Bath Body Perception Disturbance Scale (ρ = 0.491; p = 0.048). CONCLUSION Overall, we provide evidence that the pain phenotype in CRPS, i.e., spatial pain extent, might be related to sensitization mechanism within the central nociceptive system. This study points towards central neuronal excitability as a potential therapeutic target in patients with more widespread CRPS.