Temporary suppression of clonus in humans by brief photostimulation.
In this double-blind study, 21 subjects with spastic paraparesis due to chronic spinal cord injury received irradiation to the skin overlying the radial, median and saphenous nerves with a helium-neon laser (632.5 nm, 1 mW, 20 Hz) or sham treatment. Subjects in the experimental group demonstrated complete clonus suppression after 40 s of irradiation, an effect identical to that observed previously after peripheral electrical nerve stimulation. Subjects who received placebo did not demonstrate this phenomenon. Because such laser irradiation produces no detectable thermal effect, the results indicate that photochemical reactions initiated by laser may trigger neural activity.
D004311:Double-Blind Method; D004558:Electric Stimulation; D006801:Humans; D053685:Laser Therapy; D009119:Muscle Contraction / Q000528:radiation effects*; D010525:Peripheral Nerves / Q000503:physiopathology; D010775:Photic Stimulation; D011897:Random Allocation; D012018:Reflex / Q000528:radiation effects; D013119:Spinal Cord Injuries / Q000503:physiopathology / Q000628:therapy; D013997:Time Factors