Epidural Spinal Cord Stimulation Acutely Reduces Efferent Postganglionic Sympathetic Nerve Activity in Humans

Abstract

Evidence in clinical and animal studies demonstrates that epidural spinal cord stimulation (SCS) mimics the effects of sympathetic block or sympathectomy and increases peripheral blood flow. However, the extent to which SCS lowers sympathetic nerve activity in humans remains unclear because no studies have directly assessed muscle sympathetic nerve activity (MSNA) responses to SCS. We tested the hypothesis that acute SCS (60 min) at the lower thoracic spine would 1) lead to reduced MSNA in the peroneal nerve, and 2) increase blood flow in the legs, but not the arms. Twelve patients (54 ± 3 yrs, 5 men/7 women) that previously underwent surgical implantation of a SCS device for management of neuropathic pain were studied. Following 48 hours of no SCS, femoral and brachial artery blood flow was assessed using Doppler ultrasound at baseline and at 15, 30, 45, 60 min of SCS, and 15 min post SCS. MSNA was assessed using microneurography under the same conditions during a second visit (n=5). Femoral artery blood flow was significantly increased throughout SCS and 15 min post SCS (15 min: 26 ± 1%, 30 min: 32 ± 14%, 45 min: 30 ± 13%, 60 min: 26 ± 13%, 15 min post SCS: 40 ± 14% ml/min, P=0.02), but no change in brachial artery blood flow was observed (15 min: 4 ± 6%, 30 min: 5 ± 8%, 45 min: 5 ± 7%, 60 min: 7 ± 7% ml/min, 15 min post SCS: 6 ± 11% ml/min, P=0.86). MSNA was progressively reduced during SCS, reaching significance at 45 and 60 min, and returned toward baseline following SCS (15 min: −1 ± 6%, 30 min: −13 ± 4%, 45 min: −17 ± 6%, 60 min: −21 ± 7%, 15 min post SCS: −4 ± 5% bursts/100heartbeats, P=0.01). Similar results were observed for MSNA total activity (AU/min) (P<0.042). During measures of MSNA, self‐reported neuropathic pain was low at baseline and not significantly changed by SCS (scale 0–10; BL: 2.8 ± 0.8, 15 min: 1.7 ± 0.9, 30 min: 1.5 ± 1, 45 min: 1.7 ± 1, 60 min: 1.5 ± 1, P=0.07), suggesting that reductions in MSNA were SCS‐mediated and not primarily a result of pain relief. These preliminary results demonstrate proof of principle that acute lower thoracic SCS significantly reduces peroneal MSNA in humans.Support or Funding InformationAHA 17POST33440101, T32 HL07121, NHLBI (P01HL014388), U54 TR001356 and AHA (13DG143400012)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.