title: Transcutaneous spinal cord direct current stimulation inhibits the lower limb nociceptive flexion reflex in human beings.
abstract: Aiming at developing a new, noninvasive approach to spinal cord neuromodulation, we evaluated whether transcutaneous direct current (DC) stimulation induces long-lasting changes in the central pain pathways in human beings. A double-blind crossover design was used to investigate the effects of anodal direct current (2mA, 15min) applied on the skin overlying the thoracic spinal cord on the lower-limb flexion reflex in a group of 11 healthy volunteers. To investigate whether transcutaneous spinal cord DC stimulation (tsDCS) acts indirectly on the nociceptive reflex by modulating excitability in mono-oligosynaptic segmental reflex pathways, we also evaluated the H-reflex size from soleus muscle after tibial nerve stimulation. In our healthy subjects, anodal thoracic tsDCS reduced the total lower-limb flexion reflex area by 40.25% immediately after stimulation (T0) and by 46.9% 30min after stimulation offset (T30). When we analyzed the 2 lower-limb flexion reflex components (RII tactile and RIII nociceptive) separately, we found that anodal tsDCS induced a significant reduction in RIII area with a slight but not significant effect on RII area. After anodal tsDCS, the RIII area decreased by 27% at T0 and by 28% at T30. Both sham and active tsDCS left all the tested H-reflex variables unchanged. None of our subjects reported adverse effects after active stimulation. These results suggest that tsDCS holds promise as a tool that is complementary or alternative to drugs and invasive spinal cord electrical stimulation for managing pain. Thoracic transcutaneous direct current stimulation induces depression of nociceptive lower limb flexion reflex in human beings that persists after stimulation offset; this form of stimulation holds promise as a tool that is complementary or alternative to drugs and invasive spinal cord electrical stimulation for managing pain.
authors.affiliation: Unità Operativa di Neurofisiopatologia, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy Centro Clinico per la Neurostimolazione, le Neurotecnologie ed i Disordini del Movimento, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy Dipartimento di Scienze Neurologiche, Università di Milano, Milan, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Cogiamanian
authors.forename: Maurizio
authors.initials: M
authors.lastname: Vergari
authors.forename: Elena
authors.initials: E
authors.lastname: Schiaffi
authors.forename: Sara
authors.initials: S
authors.lastname: Marceglia
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ardolino
authors.forename: Sergio
authors.initials: S
authors.lastname: Barbieri
authors.forename: Alberto
authors.initials: A
authors.lastname: Priori
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007866:Leg / Q000294:innervation / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D059408:Pain Management; D012018:Reflex / Q000502:physiology*; D013116:Spinal Cord / Q000503:physiopathology*; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*; D055815:Young Adult