This open-label trial suggests benefit in pain reduction, associated CRPS symptoms, improved quality of life and ability to work following anesthetic ketamine in previously refractory CRPS patients. However, a randomized controlled trial will be necessary to prove its efficacy.

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Findings suggest that, at least at a 6-week follow up: (1) deep ketamine therapy is effective for relief of pain CRPS I and (2) there were no adverse cognitive effects of extended treatment with deep ketamine infusion. No definitive conclusions could be drawn about the relationship between mood and personality factors and the presence of CRPS I.

A B S T R A C TBackground. Previous reports have indicated that ketamine anesthesia may produce significant improvement if not complete recovery of patients with complex regional pain syndrome (CRPS). Aims.Here we report on a patient who had CRPS affecting mainly the right side of her body who underwent functional magnetic resonance imaging (fMRI) scans prior to and in the months following apparent successful treatment with anesthetic doses of ketamine.Materials and Methods. The patient underwent two imaging sessions: one during her pain state (CRPS + ) and 1 month after her ketamine treatment in her pain-free state (CRPS -).Both spontaneous and evoked (brush, cold, and heat) pain scores decreased from 7-9/10 on a visual analog scale prior to the treatment to 0-1 immediately following and for months after the treatment. For each imaging session, the identical mechanical (brush) and thermal (cold and heat) stimuli were applied to the same location (the skin of the dorsum of the right hand).Results. Comparison of CRPS + vs CRPSfor the three stimuli showed significant changes throughout the cerebral cortex (frontal, parietal, temporal, cingulate, and hippocampus), in subcortical regions such as caudate nucleus, and in the cerebellum. In addition, resting state network analysis showed a reversal of brain network state, and the recovered state paralleled specific default networks in healthy volunteers.Discussion. The observed changes in brain response to evoked stimuli provide a readout for the subjective response.Conclusion. Future studies of brain function in these patients may provide novel insight into brain plasticity in response to this treatment for chronic pain.

S(+)-ketamine can be gradually titrated to large doses (500 mg/day) without clinically relevant side effects. There was no pain relief or change in QST measurements in this series of long-standing severe CRPS patients.