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

BACKGROUND: The vasculature function is mainly regulated by the autonomic nervous system. Importantly, the sensory-motor nervous system also innervates peripheral vessels and has the capacity to modulate vascular tone. Here we investigated the effects of electrical stimulation of a mixed nerve trunk on blood flow in deep arteries and muscle perfusion. Our hypothesis is that stimulation of a mixed nerve can modify blood flow. METHODS: Twenty-nine healthy participants were included into a randomized-crossover and blinded clinical trial. Each subject received a placebo and two percutaneous peripheral nerve stimulation (pPNS) protocols on the median nerve: Pain Threshold continuous Low Frequency (PT-cLF) and Sensory Threshold burst High Frequency (ST-bHF). Blood flow was then assessed bilaterally using Power Doppler Ultrasonography at the main arteries of the arm, and blood perfusion at the forearm muscles. Afterwards, blood flow was quantified using a semi-automatized software, freely shared here. RESULTS: Placebo, consisting in needle insertion, produced an immediate and generalized reduction on peak systolic velocity in all arteries. Although nerve stimulation produced mainly no effects, some significant differences were found: both protocols increased the relative perfusion area of the forearm muscles, the ST-bHF protocol prevented the reduction in peak systolic velocity and TAMEAN of the radial artery produced by the control protocol and PT-cLF produced a TAMEAN reduction of the ulnar artery. CONCLUSIONS: Therefore, the arterial blood flow in the arm is mainly impervious to the electrical stimulation of the median nerve, composed by autonomic and sensory-motor axons, although it produces mild modifications in the forearm muscles perfusion.

Temporal Dynamics of Adverse Effects across Five Sessions of Transcranial Direct Current Stimulation.

(1) Background: Transcranial direct current stimulation (tDCS) is a safe intervention, only producing mild and transient adverse effects (AEs). However, there is no detailed analysis of the pattern of adverse effects in an application transferable to the clinic. Therefore, our objective is to describe the AEs produced by tDCS and its temporal evolution. (2) Methods: A total of 33 young volunteers were randomized into a tDCS or sham group. Participants performed a hand dexterity task while receiving the tDCS or sham intervention (20 min and 1 mA), for five consecutive days. AEs were assessed daily after each intervention and classified as somatosensory, pain, or other effects. (3) Results: The number of AEs was generally increased by tDCS intervention. Specifically, tDCS led to more frequent somatosensory discomfort, characterized by sensations like itching and tingling, alongside painful sensations such as burning, compared to the sham intervention. Additionally, certain adverse events, including neck and arm pain, as well as dizziness and blurry vision, were exclusive to the tDCS group. Interestingly, tDCS produced similar AEs across the days; meanwhile, the somatosensory AEs in the sham group showed a trend to decrease. (4) Conclusions: tDCS produces mild and temporary somatosensory and pain AEs during and across sessions. The different evolution of the AEs between the tDCS and sham protocol could unmask the blinding protocol most used in tDCS studies. Potential solutions for improving blinding protocols for future studies are discussed.

Short- and medium-term effects of a single session of pain neuroscience education on pain and psychological factors in patients with chronic low back pain. A single-blind randomized clinical trial.

INTRODUCTION: Biopsychosocial approach in patients suffering chronic low back pain (CLBP) promotes pain self-management strategies. Current evidence recommends high dose of Pain Neuroscience Education (PNE) for clinically significant differences. However, the workload and time constraints experienced by healthcare providers impede the application of the recommended treatment regimen. In fact, Back School with a biomechanical model is the main approach to manage CLBP in public systems. OBJECTIVE: The objective of this study is to explore the effect of a 60 min single session of PNE as an adjunct to back school on pain intensity and psychological variables patients with CLBP. METHODS: A double-blind, two-arm randomized controlled clinical trial was conducted in patients with CLBP who attended back school sessions held in a Spanish public hospital. A total of 121 patients were randomized into control group, who received the Back School program during 5 weeks, and intervention group, who additionally received a single session of PNE. Patient-reported outcomes were the Numerical Pain Rating Scale, Central Sensitization Inventory, Pain Catastrophizing Scale, and Tampa Scale of Kinesiophobia, with a 12-week follow-up. RESULTS: A total of 113 patients were analysed. Intervention and control group presented similar effects on pain and kinesiophobia. At follow-up, intervention group exhibited reduced sensitization and catastrophism scores compared with control, including the subscales. Additionally, PNE reduced the percentage of participants classified as having central sensitization compared with control. CONCLUSIONS: Adding a single PNE session in the back school program did not reduce pain but improved psychological factors as central sensitization and pain catastrophizing at medium-term. This study highlights the potential of PNE to optimize treatment strategies for CLBP, especially in public health centres where time resources are scarce. SIGNIFICANCE STATEMENT: Adding a single PNE session in the back school program did not reduce pain but improved psychological factors as central sensitization and pain catastrophism at medium-term.