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).
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.
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.
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.
*Danish Pain Research Center
Departments of †Neurosurgery
§Neurology, Aarhus University Hospital, Aarhus, Denmark
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K.M. designed the study with advice from all coauthors, examined and included the patients, conducted the quantitative sensory testing, and prepared the first draft of the manuscript. T.S.J. provided the original idea for the study as well as clinical and scientific advice. L.N. provided clinical and scientific advice and technical assistance. J.C.S. provided clinical and scientific advice. All authors revised, contributed to, and approved the final manuscript.
This project was carried out as part of a cofinanced PhD study funded by Aarhus University, Aarhus, Denmark, St Jude Medical, St. Paul, Minnesota and the Danish Medical Research Council, Copenhagen, Denmark. K.M. and J.C.S. have received teaching fees from St Jude Medical and are paid consultants for Biolab Technology. The other authors declare no conflict of interest.
Reprints: Kaare Meier, MD, PhD, Danish Pain Research Center, Aarhus University Hospital, Noerrebrogade 44, 1A, DK-8000 Aarhus C, Denmark (e-mail: email@example.com).
Received March 3, 2014
Received in revised form July 29, 2014
Accepted June 12, 2014