Pathophysiology and Treatment of Chronic Non-Neuropathic Pain: Which Role for Non-Invasive Brain Stimulation?

The label of chronic non-neuropathic pain includes several pathological conditions, ranging from fibromyalgia to low-back pain and irritable bowel syndrome, where pain is a prominent, highly disabling symptom. Pathophysiological mechanisms underlying these particular forms of pain--that don’t follow any clear, documentable damage at the peripheral and/or central nervous system--remain largely unexplained, and poor, often ineffective therapeutic resources are available. Very recently, magnetic resonance imaging techniques have revealed subtle structural and functional brain abnormalities in such diseases particularly affecting areas involved in pain perception and control in the domain of the so-called pain matrix. Interestingly, abnormalities of peripheral nociceptive innervation have also been found in these patients by histochemical analysis of cutaneous specimens obtained by skin biopsy.
Recent years have seen the growth of new technologies able to regulate or interfere with cortical activity based on non-invasive brain stimulation (NIBS), performed through electric or magnetic currents applied to the scalp. These approaches, namely transcranial magnetic (TMS) and electrical (tES) stimulation, are able to explore and modulate cortical excitability and have found particular interest among the scientific community and especially clinical research, thanks to their ability to induce long-lasting, persistent plastic effects that can be applied as treatment. NIBS has been employed effectively for exploring mechanisms underlying normal and pathological pain processing, and also for the treatment of different chronic neuropathic and non-neuropathic pain conditions like fibromyalgia, with encouraging--even if still inconclusive--results. Moreover, new approaches are under study that are based on combinations of NIBS with other therapeutic procedures or new stimulation paradigms (theta burst rTMS, alternate current, and random noise electrical stimulation).
In conclusion, NIBS can represent a useful complementary tool for exploring pathophysiological mechanisms of non-neuropathic pain syndromes, and for designing new appropriate and specific strategies for the clinical management and rehabilitation of these patients. As such, this Research Topic addresses the subject of non-neuropathic pain and neurostimulation, and seeks relevant and up-to-date information and knowledge about the state of the art, while also presenting perspectives for future development.