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.
Part of the book: Transcranial Magnetic Stimulation in Neuropsychiatry
The use of electricity for analgesic effects has a long history and yet currently neuromodulation devices based on electrical stimulation are typically restricted to being a last resort intervention for pain patients after the failure of pharmacological treatments. Whilst spinal cord stimulation is an established intervention for intractable neuropathic pain, the use of neuromodulation for other forms of pain and targeting different aspects of pain processing is less well established. Non-invasive neuromodulation as part of a standard intervention for pain relief would be ideal for without long term treatment of a chronic pain condition as it would avoid the inevitable side effects associated with long-term use of pharmacological interventions or interactions between different drug treatments. This is particularly relevant as chronic pain can be associated with diseases that would require pharmacological treatment for the primary condition. However, there is currently both a deficit in understanding the mechanisms of the different non-invasive devices and also in how these devices may facilitate pain relief for specific conditions. This review will focus on the application of electric currents non-invasively to different sites for pain relief and outline the future potential of these technologies.