Efficacy and safety of a single intrathecal methylprednisolone bolus in chronic complex regional pain syndrome

Activated immune cells in the spinal cord may play an important role in the development and maintenance of neuropathic pain, such as occurs in response to peripheral inflammation or tissue injury. Immune activation may therefore serve as a therapeutic target for immune modulating drugs like corticosteroids. This double-blind randomized placebo-controlled parallel-group trial aimed to investigate the efficacy and safety of a single intrathecal administration of 60 mg methylprednisolone (ITM) in chronic patients with complex regional pain syndrome (CRPS). The primary outcome measure was change in pain (pain intensity numeric rating scale; range 0-10) after 6 weeks. With 21 subjects per group the study had a 90% power to detect a clinically relevant difference (⩾2 points). After 21 patients (10 on ITM) were included, the trial was stopped prematurely after the interim analysis had shown that ITM had no effect on pain (difference in mean pain intensity numeric rating scale at 6 weeks 0.3, 95% confidence interval −0.7 to 1.3) or any other outcome measure. We did not find any difference in treatment-emergent adverse events between the ITM and placebo group. We conclude that a single bolus administration of ITM is not efficacious in chronic CRPS patients, which may indicate that spinal immune activation does not play an important role in this phase of the syndrome.