Neuropathic pain modulation after spinal cord injury by breathing-controlled electrical stimulation (BreEStim) is associated with restoration of autonomic dysfunction

Abstract

BackgroundRecent findings have implicated supraspinal origins from the pain neuromatrix– central autonomic network (PNM–CAN) in the generation of neuropathic pain (NP) after spinal cord injury (SCI). The aim of this study was to further investigate the theorized PNM–CAN mechanisms in persons with SCI by using a centrally directed pain intervention, provided by breathing-controlled electrical stimulation (BreEStim), to measure resultant autonomic changes measured by time and frequency domain heart rate variability (HRV) analysis.MethodsNull and active BreEStim interventions were administered to SCI+NP subjects (n=10) in a random order. HRV data and VAS pain scores were collected at resting pre-test and 30 minutes post-test time points. Resting HRV data were also collected from SCI–NP subjects (n=11).ResultsSCI+NP subjects demonstrated a lower baseline HRV and parasympathetic tone, via SD of the normal-to-normal intervals (SDNN) and low frequency (LF) parameters, compared with SCI–NP subjects. However, following active BreEStim, SCI+NP subjects exhibited an increase in HRV and parasympathetic tone, most notably via pairs of successive R–R beat lengths varying by greater than 50 ms (NN50) and proportion of NN50 for total number of beats (pNN50) parameters along with lower VAS scores. Additionally, the post-test SCI+NP group was found to have a statistically comparable autonomic profile to the SCI–NP group across all HRV variables, including SDNN and LF parameters.ConclusionThe analgesic effects of active BreEStim in SCI+NP subjects were associated with restoration of autonomic dysfunction in this population.

Commentry on: Combined transcranial direct current stimulation and breathing controlled electrical stimulation for the management of neuropathic pain after spinal cord injury

“…However, we do not agree with the authors that BreEStim produces analgesic effects only for the arm. Our recent series of experiments has provided evidence that BreEStim has central analgesic effects in painfree healthy subjects (7-9) and in subjects with SCI (10,11). This study provided further evidence for this central analgesic effect.…”

Central Neuropathic Mechanisms in Pain Signaling Pathways: Current Evidence and Recommendations

“…The successful activation of the pain neuromatrix–central autonomic network can be quantified by looking at combined effects on autonomics as measured by heart rate variability [ 67 ]. A small sample of patients post SCI completed a controlled trial in which the treatment group received 120 BreEStim impulses [ 67 ]. The treatment group experienced a decrease in heart rate variability, indicating that BreEStim may provide for a viable treatment strategy for decreasing post-SCI pain [ 67 ].…”

“…A small sample of patients post SCI completed a controlled trial in which the treatment group received 120 BreEStim impulses [ 67 ]. The treatment group experienced a decrease in heart rate variability, indicating that BreEStim may provide for a viable treatment strategy for decreasing post-SCI pain [ 67 ].…”

Observations of Autonomic Variability Following Central Neuromodulation for Chronic Neuropathic Pain in Spinal Cord Injury

“…Despite its high prevalence, managing persons with SCI and NP is often clinically challenging, owing largely in part to our limited understanding of its precise pathophysiology (2,3). A score of recent, innovative studies have presented increasing evidence for pathologic neuromodulation at the supraspinal level as being responsible for post-SCI NP (4)(5)(6)(7). The neural structures implicated in this pathogenesis include the insula, anterior cingulate cortex (ACC), and the prefrontal cortex, which collectively comprise part of the pain neuromatrix (PNM) (8,9).…”

“…Furthermore, elegantly designed studies utilizing functional MRI found these cortical areas within the PNM to demonstrate increased activity specifically in persons with SCI + NP relative to able bodied persons (AB) upon pain induction (4). These neural structures also were found to be highly interconnected in proximity and function to the central autonomic network (CAN) in persons with SCI relative to AB persons (4,5,(13)(14)(15).…”