Efficacy of anodal transcranial direct current stimulation (tDCS) for the treatment of fibromyalgia: results of a randomized, sham-controlled longitudinal clinical trial

Abstract

Fibromyalgia has been recognized as a central pain disorder with evidence of neuroanatomic and neurophysiologic alterations. Previous studies with techniques of noninvasive brain stimulation--transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS)--have shown that these methods are associated with a significant alleviation of fibromyalgia-associated pain and sleep dysfunction. Here we sought to determine whether a longer treatment protocol involving 10 sessions of 2 mA, 20 min tDCS of the left primary motor (M1) or dorsolateral prefrontal cortex (DLPFC) could offer additional, more long-lasting clinical benefits in the management of pain from fibromyalgia. METHODS: Forty-one women with chronic, medically refractory fibromyalgia were randomized to receive 10 daily sessions of M1, DLPFC, or sham tDCS. RESULTS: Our results show that M1 and DLPFC stimulation both display improvements in pain scores (VAS) and quality of life (FIQ) at the end of the treatment protocol, but only M1 stimulation resulted in long-lasting clinical benefits as assessed at 30 and 60 days after the end of treatment. CONCLUSIONS: This study demonstrates the importance of the duration of the treatment period, suggesting that 10 daily sessions of tDCS result in more long lasting outcomes than only five sessions. Furthermore, this study supports the findings of a similarly designed rTMS trial as both induce pain reductions that are equally long-lasting.

Figure 1

Mean pain scores associated with the three conditions of stimulation: left M1 (primary motor cortex); left DLPFC (dorsolateral prefrontal cortex); and sham tDCS. Pain scores are reported on the Visual Analogue Scale for Pain; 0= no pain, 10= worst pain of life. * Indicates statistically significant (p<0.05) as compared with baseline. Each column represents mean score SEM (standard error of mean). T1: end of stimulation, T2: 30 day follow-up, T3: 60 day follow-up.

Figure 2

Mean fibromyalgia impact scores associated with the three conditions of stimulation: left M1 (primary motor cortex); left DLPFC (dorsolateral prefrontal cortex); and sham tDCS. The Fibromyalgia Impact Questionnaire (FIQ) quantitates the overall impact of fibromyalgia over many dimensions (e.g. physical functioning, pain level, fatigue, sleep disturbance, psychological distress, etc.) and has been extensively validated; 0= no impact on quality of life, 100= worst impact possible. * Indicates statistically significant (p<0.05). ns – indicates not significant (p>0.05). Each column represents mean FIQ score SEM (standard error of mean). T1: end of stimulation, T2: 30 day follow-up, T3: 60 day follow-up.