Motor cortex tRNS improves pain, affective and cognitive impairment in patients with fibromyalgia: preliminary results of a randomised sham-controlled trial

Objective. Fibromyalgia (FM) is a clinical syndrome characterised by widespread musculoskeletal pain, chronic fatigue, cognitive deficits, and sleep and mood disorders. The effectiveness of most pharmacological treatments is limited, and there is a need for new, effective and well-tolerated therapies. It has recently been shown that transcranial direct-current stimulation (tDCS) of the motor cortex reduces pain, and that tDCS of the dorso-lateral prefrontal cortex (DLPFC) improves anxiety, depression and cognitive impairment in FM patients. The new technique of transcranial random noise stimulation (tRNS) using randomly changing alternating currents has very recently been shown to improve working memory and pain in limited series of patients with FM or neuropathic pain. The aim of this study was to investigate the clinical effects of primary motor cortex (M1) tRNS in FM patients. Methods. Twenty female FM patients aged 26-67 years were randomised to undergo active (real) or placebo (sham) tRNS sessions on five days a week (Monday-Friday) for two weeks. Each patient was evaluated before and after treatment using a visual analogue scale (VAS), the Fibromyalgia Impact Questionnaire (FIQ), the Hospital Anxiety and Depression Scale (HADS), the Trail Making Test (TMT), the Rey Auditory Verbal Learning Test (RAVLT), the Forward and Backward Digit Span test, and the FAS verbal fluency test. Results. In comparison with sham treatment, active tRNS of M1 induced a general improvement in the clinical picture of FM, with a significant reduction in pain, depression, anxiety and FIQ scores and a significant improvement in TMT (A), RAVLT and FAS scores. Conclusion. These findings suggest that tRNS of M1 can be very effective in relieving FM symptoms. Unlike motor cortex tDCS, it seems to counteract both pain and cognitive disturbances, possibly because the invoked mechanism of stochastic resonance synchronises neural firing and thus leads to more widespread and lasting effects.