Mechanisms and Clinical Applications of Transcranial Direct Current Stimulation in Treating Patients with Firbomyalgia

Fibromyalgia, presenting as widespread pain, sleep problems and impaired daytime functioning, can cause long term disability and impaired quality of life. The prevalence of fibromyalgia was reported to be about 2 % inWestern population. The pathomechanism for fibromyalgia is still not well-known. Global allodynia and hyperalgia are the hallmarkers of fibromyalgia. Therefore, fibromyalgia is considered to be as a human model disease of central sensitization. Neuro-endocrine, autonomic and neuro-image abnormality are demonstrated in recent studies. Lower serotonin and higher substance P level was found in serum and CSF in the patients with fibromyalgia. It has been observed fibromyalgia patients have abnormal autonomic responses to stress. In addition, a depressed hypothalamus- pituitary-adrenal axis was also reported in the patients with fibromyalgia. Regional-specific abnormality in CNS was demonstrated in the functional magnetic resonance image study in patients with fibromyalgia. Unfortunately, there is still no curable treatment available to fibromyalgia. Recently, serotonin-norepinephrine reuptake inhibitor (SNRI) was reported to have promising effects in in the patients with fibromyalgia. However, the data regarding long-term effects and in Chinese population of SNRI are still lacking. Non-pharmacological approaches including physical modality, hydrotherapy, exercise and cognition behavior therapy (CBT) also play some roles in managing the patients with fibromyalgia. Nevertheless, the treatment for most of fibromyalgia patients is still a challenging topic. Transcranial direct current stimulation (tDCS) can change the excitability of regional cortex. According to the polarity of the electrode, inhibitory and excitatory effects can be achieved. tDCS has been applied in clinical conditions such as depression, insomnia, anxiety, stroke and pain disorders and showed some positive effects. Few studies reported treating fibromyalgia by applying tDCS and observed favorable effects. However, the data regarding the optimal model of tDCS in fibromyalgia is still lacking. Furthermore, the effects in neuro-endocrine and neuro-image of applying tDCS in fibromyalgia are also unknown. Finally, the using tDCS in Chinese population with fibromyalgia is unavailable. We propose that applying tDCS could be effective to reduce the symptoms and favorable effects in patients with fibromyalgia via neuromodulation effects.We also propose that by applying tDCS could induce favorable changes in both autonomic function and neuro-endocrine status. We also plan to demonstrate the changes of neuro-image in the patients with fibromyalgia receiving tDCS in light of pathomechanism of fibromyalgia. We will exam our hypothesis by a series of prospective double-blinded control trials in this three-year project. The series of studies in this project can help us to exam the effectiveness and understand the pathomechanism of tDCS in treating fibromyalgia.