Nociceptive muscle reflex responses in human forearms

In healthy volunteers, 5-min noxious stimulation with rectangular electrical pulses applied transcutaneously to the phalanges enhanced tonic activity in the palmar and finger flexor muscles resulting in a specific electromyographic pattern consisting of two successive bursts of activity which appeared after a period of inhibition. In patients with chronic pain in the arm, significantly lower thresholds for the first and the second waves of reflex activity have been found. This electromyographic pattern of the forearm muscle reflex responses is supposed to be similar to the nociceptive flexor reflex in the leg. It can be useful for objective assessment of the effectiveness of analgesia and pain syndrome therapy in patients with cervical spinal cord injury.