Peripheral nerve neurostimulation inhibits pain and nociception in an advanced human experimental model

Electrical peripheral nerve neurostimulation (PNS) is reported to be an effective pain treatment though an objective proof of antinociceptive effect is lacking. The human experimental study addressed PNS effects on nociception objectivated by electrophysiology and on pain by psychophysics. In 23 healthy volunteers 39 sessions were performed. Three experiments (PNS ipsilateral, PNS contralateral, Control) consisted of 13 sessions each. Conditioning PNS (100 Hz) of left (PNS ipsilateral) or right (PNS contralateral) superficial radial nerve trunk (radialis) evoked non-painful, tingling sensations on the hand dorsum. Local cutaneous anesthesia at PNS site provided for preferential nerve trunk stimulation. Cortical laser-evoked potentials (LEP) after painful stimulation at left hand dorsum as well as mechanical thresholds were recorded at the same site before (T1), during (T2), and after (T3) PNS or a no stimulation period (Control). LEP amplitude decreased independently of PNS site. Exclusively with ipsilateral PNS, N2 latency increased, laser ratings and mechanical detection threshold (MDT) decreased. Divergent and common effects of ipsi- and contralateral PNS suggest a combination of peripheral and central antinociceptive mechanisms. The study in man documents inhibition of nociception and pain by PNS and provides with an experimental model for future objectives in neuromodulation.