A small controlled trial found that intravenous immunoglobulin infusion (IVIG) reduced pain intensity in the complex regional pain syndrome (CRPS).

CRPS is difficult to treat, however preliminary evidence suggests an immune system component to the syndrome. This preliminary trial aimed to determine whether IVIG was effective in reducing pain in patients with long-standing CRPS. Participants had refractory CRPS lasting 6 to 30 months, with pain scores of at least 4 (on a 0-10 scale). They were randomised to IVIG 0.5g/kg or placebo (IV 0.9% saline) on a crossover basis, at least 28 days apart. Primary outcome was pain intensity 6 to 19 days after each infusion.

There were 13 people randomised, of whom 12 completed the study. Average pain intensity was lower after IVIG than after placebo, by 1.55 units (95% CI, 1.29 to 1.82; P < 0.001). Three patients reported a 50% or greater reduction in pain score after IVIG. 

The authors conclude that in this study of patients with CRPS, IVIG reduced pain score to a greater extent than placebo. They caution that the study was small, and thus prone to bias and the play of chance: further studies are therefore needed to confirm the effect and establish the optimum dose and duration of treatment.

An accompanying editorial discusses the trial: the authors welcome the study but caution that it is preliminary and has limitations that must be recognised.