Effects of paired-pulse transcranial magnetic stimulation of the motor cortex on perception of experimentally induced pain.

Objective: We investigated the influence of paired-pulse transcranial magnetic stimulation (ppTMS) of the motor cortex (M1) on perception of noxious electrical stimuli. The nociceptive flexion reflex response was assessed to determine spinal effects.

Methods: In the first experiment, the effect of ppTMS of M1 on perception of noxious stimulation of the sural nerve was assessed by varying the stimulus onset asynchronies (SOAs) and the order of the stimulations (-400, -75, -25, 25, 125, 400 ms and control ppTMS, negative sign: ppTMS precedes the noxious stimulation).

High-frequency rTMS of the motor cortex does not influence the nociceptive flexion reflex but increases the unpleasantness of electrically induced pain.

The aim of this study was to investigate whether a 10-Hz repetitive transcranial magnetic stimulation (rTMS) applied over the motor cortex, using a stimulus paradigm employed for pain control in chronic pain, affects acute electrically induced pain. We investigated whether rTMS modulates the nociceptive flexion reflex (NFR) in addition to subjective pain perception. Pain threshold, NFR threshold, supra-threshold NFR response, and the concomitant pain intensity and pain unpleasantness visual analogue scale (VAS) scores were compared before and after 20 min of rTMS.