Pressure Pain Thresholds Increase after Preconditioning 1 Hz Repetitive Transcranial Magnetic Stimulation with Transcranial Direct Current Stimulation

Abstract

BackgroundThe primary motor cortex (M1) is an effective target of non-invasive cortical stimulation (NICS) for pain threshold modulation. It has been suggested that the initial level of cortical excitability of M1 plays a key role in the plastic effects of NICS.ObjectiveHere we investigate whether transcranial direct current stimulation (tDCS) primed 1 Hz repetitive transcranial magnetic stimulation (rTMS) modulates experimental pressure pain thresholds and if this is related to observed alterations in cortical excitability.Method15 healthy, male participants received 10 min 1 mA anodal, cathodal and sham tDCS to the left M1 before 15 min 1 Hz rTMS in separate sessions over a period of 3 weeks. Motor cortical excitability was recorded at baseline, post-tDCS priming and post-rTMS through recording motor evoked potentials (MEPs) from right FDI muscle. Pressure pain thresholds were determined by quantitative sensory testing (QST) through a computerized algometer, on the palmar thenar of the right hand pre- and post-stimulation.ResultsCathodal tDCS-primed 1 Hz-rTMS was found to reverse the expected suppressive effect of 1 Hz rTMS on cortical excitability; leading to an overall increase in activity (p<0.001) with a parallel increase in pressure pain thresholds (p<0.01). In contrast, anodal tDCS-primed 1 Hz-rTMS resulted in a corresponding decrease in cortical excitability (p<0.05), with no significant effect on pressure pain.ConclusionThis study demonstrates that priming the M1 before stimulation of 1 Hz-rTMS modulates experimental pressure pain thresholds in a safe and controlled manner, producing a form of analgesia.

Differential effects of cathodal transcranial direct current stimulation of prefrontal, motor and somatosensory cortices on cortical excitability and pain perception – a double‐blind randomised sham‐controlled study

“…So, our hypothesis, in which we assumed that c‐tDCS of these cortical sites increases P p Th, was not supported by the results. These findings are in line with the results of other c‐tDCS studies assessing the effects of M1 and S1 c‐tDCS on mechanical quantitative sensory testing parameters such as mechanical pain sensitivity, pressure pain threshold and wind‐up ratio (Rogalewski et al ., ; Bachmann et al ., ; Moloney & Witney, ). In contrast, Bachmann et al .…”

The effects of anodal-tDCS on corticospinal excitability enhancement and its after-effects: conventional vs. unihemispheric concurrent dual-site stimulation

“…Recent fMRI studies showed that a-tDCS increases corticospinal excitability (CSE) of both local stimulated and distant areas, probably through interconnections between them (Meyerson et al, 1993 ; Lang et al, 2005 ). Literature indicates that tDCS induces CSE enhancement in M1, which could be used as a priming or stand-alone technique in therapeutic scenarios including improvement of motor function (Goodwill et al, 2013 ; Williams et al, 2013 ; Dutta et al, 2014 ; Filmer et al, 2014 ; Ludemann-Podubecka et al, 2014 ), motor learning (Kuo et al, 2008 ; Stagg and Nitsche, 2011 ; Zimerman et al, 2012 ; Karok and Witney, 2013 ; Vollmann et al, 2013 ; Meinzer et al, 2014 ; Parasuraman and Mckinley, 2014 ), and pain management (Bolognini et al, 2013 ; Bae et al, 2014 ; Foerster et al, 2015 ; Hagenacker et al, 2014 ; Moloney and Witney, 2014 ; Vaseghi et al, 2014 ; Wang et al, 2014 ; Zmigrod, 2014 ).…”

Neurostimulation Techniques for the Modulation of Pain

“…This manipulation of effects is based on the conceptual form of brain plasticity, "homeostatic plasticity" [82]. This protocol has been applied to the modulation of pain, and weak tDCS (1 mA) was used to "precondition" the brain to enhance the effects of subsequent stimulation via low-frequency rTMS (1 Hz) on the modulation of thermal sensation, thermal pain thresholds, and pressure pain thresholds, thereby producing a form of analgesia [83,84].…”

“…This is best demonstrated in studies regarding application to the human motor cortex, where they attempt to direct the current to strictly follow the orientation of axons and/or dendrites in the induced electrical field [61]. Recent studies employ current flow models with defined montages [86] and use improved electrode positioning through the use of caps based on the international 10-20 positioning system [84].…”