Sensorimotor effects of plasticity‐inducing percutaneous peripheral nerve stimulation protocols: a blinded, randomized clinical trial

Abstract

Background Electrical stimulation of skin afferents can induce somatosensory plasticity in humans. Nevertheless, it is unknown if this is possible to do through percutaneous stimulation of a peripheral nerve, which will allow for regional anaesthesia interventions. Furthermore, potentiation protocols applied over mainly non‐nociceptive fibres inhibit nociception in rodents, but this has not been tested in humans. Objective To determine whether a protocol aiming to depress the nociceptive circuit and another aiming to potentiate non‐nociceptive circuits produce regional hypoalgesia and changes in motor function, applied through percutaneous peripheral nerve stimulation (pPNS), and to assess which of them is more promising for pain relief, immediately and 24 h after the intervention. Methods PT‐cLF protocol aims to depress the nociceptive pathway through Pain Threshold, continuous Low Frequency stimulation and ST‐bHF aims to produce potentiation of the non‐nociceptive pathway, through Sensory Threshold burst stimulation at High Frequency. All subjects (n = 29) went through both protocols and a control condition in a randomized and blinded crossover design. Results Compared to control, ST‐bHF induced distal hypoalgesia, towards electrical (p = 0.04) and mechanical stimuli (p = 0.02) and produced mechanical hypoesthesia (p = 0.02). Contrarily, hypoalgesia was not observed after PT‐cLF (p > 0.05) but increased electrical motor threshold (p = 0.04), reduced motor recruitment (p = 0.03), and the subjects reported feeling reduced strength (p < 0.01). Conclusion This works provides evidence that is possible to induce antinociceptive plasticity in a wide territory using pPNS. Moreover, it demonstrates for the first time in humans that a protocol aiming to produce long‐term potentiation applied predominantly over non‐nociceptive afferents induces hypoesthesia and hypoalgesia.

Blood flow effects of percutaneous peripheral nerve stimulation. A blinded, randomized clinical trial

“…The exclusion criteria were as follows: being physically inactive (<150 min of moderate-intensity activity per week); upper limb pathology; any disease discouraging electrical stimulation and/or needle insertion such as coagulation deficits or belonephobia; any pathological condition such as immunodepression, chronic pain, circulatory problems or neurological disease 11,12 ; taking anticoagulants or pharmacological pain treatment (NSAIDs <24 h or opioids); being a professional athlete or being pregnant. 10,13 Participants signed an informed consent in accordance with the Helsinki Declaration. This study was approved by the Ethical Committee of Pharmacological Research in the General University Hospital of Elche, Alicante, Spain, and preregistered in clini caltr ials.gov (NCT04475133).…”

“…Specifically, to adjust the ST-bHF protocol to 16 min, the current intensity was 0 during the first 11 min of intervention 10 (Figure 2B), and then the protocol, of 5 min duration, started. The absolute intensity thresholds necessary to cause the desired perceptions using these protocols have been previously reported in Beltrá et al 10 Following every intervention, the researcher applied pressure to the needle insertion site for 1 min to prevent F I G U R E 1 Consort flow diagram for dropouts and sample management. All subjects received all three protocols, and a single dropout was produced prior to assignation due to daily intake of NSAIDs.…”

“…Power Doppler ultrasonography was performed with a high-resolution ultrasonogram (LOGIQ S7 Expert/ Pro, Soma Tech Intl, Bloomfield, EEUU) using a multifrequency linear transducer (7)(8)(9)(10)(11)(12)(13)(14). The probe position was standardized with a mark on the skin and a constant angle of insonation <60°.…”

“…Sample size was calculated based on a previous work, 18 resulting in 10 subjects with an alpha error of 5%, 80% statistical power and an effect size of f = 2.1 for the primary outcome (PSV at brachial artery) using GPower. 19 However, since this work was part of a larger clinical trial project measuring other variables, we recalculated the sample size for the primary outcome (f = 0.35, mechanical punctate pain threshold of the third fingertip 10 ). We obtained a sample size of 25 subjects.…”

“…To this end, we studied the effects on arterial blood flow and muscle perfusion of two pPNS protocols, for which both pain relief and motor effects have been previously reported. 10 pPNS and a placebo intervention were applied over the median nerve of healthy subjects, and blood flow was assessed using power Doppler ultrasonography. Our hypothesis is that pPNS will modify blood flow in deep structures, due to the close interaction between autonomic and sensory innervation and the vascular function of the blood vessels.…”