Effect of spinal cord stimulation on sensory characteristics: a randomized, blinded crossover study.

OBJECTIVES Spinal cord stimulation (SCS) is increasingly used to treat various chronic pain conditions. One undetermined issue is to what extent SCS alters the processing of sensory information from the periphery, including those stimuli that are mediated by small-fiber populations. We aimed to investigate these possible changes using quantitative sensory testing (QST). METHODS Fourteen patients in long-term SCS treatment for complex regional pain syndrome (n=5) or pain following peripheral nerve injury (n=9) were examined with QST. All patients answered questions about their pain and underwent QST while the SCS treatment was activated and deactivated (12 h interval between the sessions) in a randomized, double-blinded crossover setting. Both the painful side and the corresponding contralateral side were examined. RESULTS Thermal and mechanical thresholds were similar during SCS activation and deactivation. The same result was found for intensity of pain and areas with painful symptoms even though all patients had documented long-term benefit of the treatment. DISCUSSION The results support existing evidence suggesting that SCS does not change sensory characteristics, which is important information for both patients and clinicians. Changes in pain intensity after deactivation of SCS may be different in short-term and long-term SCS treatment.