Abstract
Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability. A small number of studies suggested that tDCS modulates the response to experimental pain paradigms. No trials have been conducted to evaluate the response of patients already suffering from pain, to an additional experimental pain before and after tDCS. The present study investigated the effect of a single session of anodal, cathodal and sham stimulation (15 mins/1 mA) over the primary motor cortex on the perceived intensity of repeated noxious thermal and electrical stimuli and on elements of quantitative sensory testing (thermal pain and perception thresholds) applied to the right hand in 15 patients with chronic low back pain. The study was conducted in a double-blind sham-controlled and cross-over design. No significant alterations of pain ratings were found. Modalities of quantitative sensory testing remained equally unchanged. It is therefore hypothesized that a single 15 mins session of tDCS at 1 mA may not be sufficient to alter the perception of experimental pain and in patients with chronic pain. Further studies applying repetitive tDCS to patients with chronic pain are required to fully answer the question whether experimental pain perception may be influenced by tDCS over the motor cortex.
Highlights
Transcranial direct current stimulation is a non-invasive brain stimulation technique that modulates the neuronal resting membrane potential and thereby affects neuronal activity [1]
Cortical excitability increases during anodal stimulation and is reduced during cathodal stimulation as confirmed by changes of magneto-electric evoked potentials [3] and activation of the motor cortex in functional magnetic resonance imaging [4]
Our workgroup conducted a clinical trial that attempted to replicate these effects but found that experimental pain as well as quantitative sensory testing results remained unaffected by a single session of anodal Transcranial direct current stimulation (tDCS) to the motor cortex in healthy participants [10]
Summary
Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that modulates the neuronal resting membrane potential and thereby affects neuronal activity [1]. As chronic noxious input causes widespread structural changes to the brain [18,19,20] and extensive functional changes to the nociceptive system [21,22,23,24], it is tempting to speculate that effects of tDCS could be more pronounced in patients with chronic pain compared to healthy participants To date this has only been examined in repetitive transcranial magnetic brain stimulation (rTMS) of the motor cortex: a recent study has shown an attenuation of experimental hand pain in chronic neuropathic pain [25]. This study investigates whether tDCS reduces the perceived intensity of experimental pain (thermal and electrical) and modalities of quantitative sensory testing (thermal pain and perception thresholds) in patients with chronic low back pain
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