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Effects of Spinal Cord and Peripheral Nerve Stimulation Reflected in Sensory Profiles and Endogenous Pain Modulation

Meyer-Frießem, Christine H., Dr.Med.*,†; Wiegand, Theresa, MD; Eitner, Lynn, MD; Maier, Christoph, Dr.Med., PhD; Mainka, Tina, Dr.Med.†,‡; Vollert, Jan, Dr.Sc.Hum.†,§; Enax-Krumova, Elena K., Dr.Med.

doi: 10.1097/AJP.0000000000000661
Original Articles
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Objectives: Spinal cord and peripheral nerve stimulation (SCS/PNS) may alleviate chronic pain; however, the underlying mechanisms remain controversial. The aim of this observational study was to assess sensory changes in the ON-conditions and OFF-conditions to obtain insights into the mechanism of analgesic effects of SCS/PNS.

Materials and Methods: We contacted 85 patients and selected 28 patients with sufficient pain relief by SCS (n=15) or PNS (n=13) to assess their ongoing pain intensity (Numerical Rating Scale, 0 to 10), pain thresholds using Quantitative Sensory Testing (DFNS-protocol), and conditioned pain modulation (CPM) in a nonrandomized manner 2 to 4 hours after SCS/PNS deactivation (OFF-condition) and during stimulation (ON-condition). For each patient, the number of abnormally decreased pain thresholds, the presence of dynamic mechanical allodynia, and/or increased pain sensitivity was additionally totaled OR summed.

Results: In the ON-condition, pain intensity decreased (Numerical Rating Scale SCS: 6.5±2.1 vs. 3.7±2.3, P<0.01; PNS: 6.2±1.4 vs. 4±1.9, P<0.01), but this did not correlate with any single sensory parameter. However, for SCS, the total number of parameters indicating hyperalgesia was significantly reduced in the ON-condition (45 vs. 23, P=0.001). A smaller CPM effect in the OFF-condition correlated with a greater CPM improvement during stimulation (SCS: r=−0.741, P=0.002; PNS: r=−0.773, P=0.003), independently from the spontaneous pain intensity.

Discussion: The analgesic effect of SCS/PNS did not correlate with changes of single sensory parameters, but SCS/PNS reduced the number of abnormal hyperalgesic findings disregarding the kind of applied stimuli, suggesting a general antihyperalgesic effect. In addition, stimulation improved the endogenous pain inhibition. Both findings indicate that SCS/PNS may modulate central circuits.

*Department of Anaesthesiology, Intensive Care Medicine, Palliative Care Medicine and Pain Management, Medical Faculty of Ruhr-University, Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil GmbH Bochum

Department of Pain Medicine

Department of Neurology, Ruhr-University Bochum, BG-Kliniken Bergmannsheil, Bochum, Germany

Department of Neurology, Charité University Medicine Berlin, Berlin, Germany

§Pain Research, Department of Surgery and Cancer, Imperial College, London, UK

C.H.M.-F and T.W.: contributed equally.

The manuscript is part of T.W.’s doctoral thesis.

C.H.M.-F: drafted the manuscript. T.W.: collected the data, drafted the manuscript, and carried out the statistical analyses. L.E.: participated in drafting the manuscript. C.M.: responsible for the concept. T.M.: drafted the ethical proposal. J.V.: carried out the statistical analyses. E.K.E-K: responsible for the concept, gave advice, and made revisions.

The authors declare no conflict of interest.

Reprints: Christine H. Meyer-Frießem, Dr.Med., Department of Anesthesiology, Intensive Care Medicine, Palliative Care Medicine and Pain Management, BG Universitätsklinikum Bergmannsheil gGmbH, Bürkle-de-la-Camp Platz 1, Bochum 44789, Germany (e-mail: meyer-friessem@ains-bergmannsheil.de).

Received May 31, 2018

Received in revised form September 7, 2018

Accepted September 15, 2018

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