Sorel M, et al. - The value of three-phase bone scintigraphy (TPBS) in assessing the efficacy of ketamine in relieving complex regional pain syndrome (CRPS) was assessed. They performed TPBS in 105 patients with unilateral, focal CRPS of type 1 before 5 days of ketamine infusions. The relative hyperfixation of the radioactive tracer in the limb region concerned by CRPS in phases 2 and 3 vs phase 1 of TPBS seemed to have a positive correlation with the analgesic efficacy of ketamine. This is the first study demonstrating the potential predictive value of TPBS regarding ketamine therapy outcome. In addition, the outcome support that the analgesic action of ketamine involves “central” mechanisms as well as “peripheral” mechanisms related to tissue inflammation and bone remodeling.