Neurostimulation Techniques for the Modulation of Pain

Abstract

Non-invasive brain stimulation (NIBS) is increasingly proposed as a therapeutic intervention for many neurological and psychiatric disorders, including pain, depression, obsessive compulsive disorder, and anxiety. While neuromodulation as an intervention for pain relief has a well-established scientific basis, evidence is largely restricted to invasive stimulation that targets the spinal cord. Novel non-invasive methodologies instead predominately target cortical processing of pain and thus raise interesting questions about how the most effective pain relief can be achieved. Functional magnetic resonance imaging (fMRI) studies show a widespread and distributed activation of brain areas during pain. This diverse activity is often referred to as the "pain neuromatrix" and can lead to the proposal for different possible target areas for pain relief. Neuromodulation could target brain regions of pain processing areas responsible for sensorimotor processing or alternatively regions responsible for the affective and evaluative aspects of the subjective pain experience. The chapter addresses the different approaches currently taken in the use of non-invasive neuromodulation for altering pain both in an experimental setting and the challenges involved in the translation of these techniques to a diverse range of chronic pain conditions.

Transcranial Direct Current Stimulation to Improve the Dysfunction of Descending Pain Modulatory System Related to Opioids in Chronic Non-cancer Pain: An Integrative Review of Neurobiology and Meta-Analysis

“…Studies using in vivo magnetic resonance spectroscopy (MRS) found that anodal tDCS reduces local cortical GABA concentration in the motor cortex (Stagg et al, 2009; Kim et al, 2014), it also increases local levels of glutamate and glutamine (Glx) in the intraparietal and prefrontal cortex measured together as combined Glx, and N-acetyl aspartate (NAA) (Clark et al, 2011; Hone-Blanchet et al, 2016). While studies that have investigated the effect of tDCS have found cathodal tDCS conduct to a significant decrease in glutamate concentration compared to s-tDCS (Witney, 2018). The tDCS effect on corticospinal excitability was blocked by the NMDA-receptor antagonist dextromethorphan (Liebetanz et al, 2002).…”

From Mechanisms to Analgesia: Towards the Use of Non-Invasive Neuromodulation for Pain Relief in the Clinic

“…The motor cortex represents a cortical region with high intra-cortical connectivity as well as connectivity to sub-cortical regions. There are a number of explanations for the efficacy of M1 stimulation [25]. M1-thalamic connectivity is thought to be particularly significant in neuromodulation effects [26].…”

“…As well as M1 stimulation influencing descending pain pathways it is possible that prefrontal stimulation may also modulate PAG due to the known connectivity [47]. Prefrontal tDCS is a common target for tDCS for pain modulation [25,48], but not currently assessed in the context of descending pain pathways as monitored via CPM protocols. However patient studies using tDCS of the left dorsolateral prefrontal cortex have suggested efficacy is achieved via enhancement of descending pain modulation as well as known cognitive effects of this stimulation [49].…”