Somatosensory burst peripheral nerve stimulation focally upregulates corticospinal and spinal excitability in the upper limb: a randomized crossover pilot study

Background Peripheral nerve stimulation (PNS) is commonly used in research and clinical settings for pain management and for augmenting somatosensory inputs for motor recovery. Its functional effects are dependent on stimulation parameters such as frequency, intensity, and duration of stimulation. Recently, interest in temporally modulated PNS (burst PNS), where high-frequency carrier pulses are demodulated to low-frequency bursts, has increased. Burst PNS applied below the motor threshold (sensory) have been used for pain and tremor suppression. However, the effects of burst sensory PNS (sPNS) on corticospinal and spinal excitability are unknown, limiting their application. Methods We evaluated the impact of a session of burst sPNS on corticospinal excitability through motor-evoked potentials (MEPs) and on spinal excitability through F-wave and H-reflex assessments targeting the first dorsal interosseous (FDI) and flexor carpi radialis (FCR) muscles. Ten healthy participants underwent a randomized crossover study with two experimental visits, where corticospinal and spinal excitability were evaluated before and after a session (40 min) of burst sPNS at the wrist or no stimulation (control). Results Compared with the control condition, burst sPNS resulted in a focal increase in MEP amplitudes (p < 0.001) in the FDI muscle but not in the FCR muscle (p = 0.26). Similarly, only the F-wave amplitude increased following burst sPNS (p = 0.008) for the FDI muscle compared with the control condition, but no differences were observed in the H-reflex amplitude (p = 0.33) in the FCR muscle between the burst sPNS and the control condition. Conclusion Our findings suggest that burst sPNS might modulate spinal and/or cortical excitability in the short term (5–10 min in this study). However, the relative changes in cortical and spinal levels due to burst sPNS are unknown, and the timeline for these continued aftereffects needs further investigation. Trial registration NCT04501133