1-way analysis of variance, t-tests, significance level: 0.05. In the dark, CRPS patients displayed a significantly larger leftward spatial bias when estimating their vSM, compared to pain controls and healthy subjects, and also reported lower motor function than pain controls. For right-affected CRPS patients only, the deviation of the vSM correlated significantly with the severity of distorted body perception. Results confirm previous findings of impaired visuospatial perception in CRPS patients, which might be the result of the involvement of supraspinal mechanisms in this pain syndrome. These mechanisms might accentuate the leftward bias that results from a right-hemispheric dominance in visuospatial processing and is known as pseudoneglect. Pseudoneglect reveals itself in the tendency to perceive the midpoint of horizontal lines or the subjective body midline left of the centre. It was observable in all 3 groups, but most pronounced in CRPS patients, which might be due to the cortical reorganisation processes associated with this syndrome.

There is evidence that inflammatory processes are involved in at least the early phase of complex regional pain syndrome (CRPS). We compared a panel of pro- and antiinflammatory cytokines in skin blister fluids and serum from patients with CRPS and patients with upper-limb pain of other origin (non-CRPS) in the early stage (< 1 year) and after 6 months of pain treatment. Blister fluid was collected from the affected and contralateral nonaffected side. We used a multiplex-10 bead array cytokine assay and Luminex technology to measure protein concentrations of the cytokines interleukin-1 receptor antagonist (IL-1RA), IL-2, IL-6, IL-8, IL-10, IL-12p40, and tumor necrosis factor-alpha (TNF-α) and the chemokines eotaxin, monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1β (MIP-1β). We found bilaterally increased proinflammatory TNF-α and MIP-1β and decreased antiinflammatory IL-1RA protein levels in CRPS patients compared to non-CRPS patients. Neither group showed side differences. After 6 months under analgesic treatment, protein levels of all measured cytokines in CRPS patients, except for IL-6, significantly changed bilaterally to the level of non-CRPS patients. These changes were not related to treatment outcome. In serum, only IL-8, TNF-α, eotaxin, MCP-1, and MIP-1β were detectable without intergroup differences. Blister fluid of CRPS patients showed a bilateral proinflammatory cytokine profile. This profile seems to be relevant only at the early stage of CRPS. Almost all measured cytokine levels were comparable to those of non-CRPS patients after 6 months of analgesic treatment and were not related to treatment outcome.

These findings resemble our findings in the motor system and strongly support the hypothesis of a bilateral complex impairment of central motor-sensory circuits in CRPS I.

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