Study of effect of slow frequency repeated transcranial magnetic field on modulation of pain in fibromyalgia patients

Fibromyalgia is a chronic pain syndrome characterized by diffuse musculoskeletal pain, fatigue, disturbed sleep, distress and tenderness at 11 to 18 specific locations. The etiology is largely unknown but central pain processing system and neuro-hormonal axis are found to be abnormal in fibromyalgia patients. There is a lack of appropriate management of pain and associated emotional component except symptomatic relief. This experiment was conducted to assess the efficacy of low frequency repeated transcranial magnetic stimulation (rTMS) (0.5 Hz, 90% of resting motor threshold) in fibromyalgia patients. One hundred eighteen patients were randomly assigned to receive 20 sessions of sham or real repeated transcranial magnetic stimulation (rTMS) on the right dorsolateral prefrontal cortex (RDLPFC). Pre and post rTMS at wk 0, 4 and 6, pain was assessed objectively by nociceptive flexion reflex (RIII reflex) from left biceps femoris muscle; the emotional component of pain by Beck Depression Inventory second edition (BDI-II) and strategies for coping with pain by Coping Strategy Questionnaire (CSQ), while pain modulation by diffuse noxious inhibitory control (DNIC). Post-TMS (wk6), RIII threshold increased (p<0.01) in real rTMS groups from 27.4±5.5V to 36.7±5.87V indicating analgesic effect of rTMS, while it did not (p<0.62) change (28.6±6.04V to 29.1±5.5V) in sham group. The latency of RIII also increased (p<0.045) from 108.29±34.34ms to 123.56±28.41ms, post-TMS but not post-sham (112.37±28.65 to 109.78±30.21, p<0.84), while BDI-II score (12.46±3.21) at wk 0 which reduced (p<0.03) post-TMS to 7.45±1.87. The study showed that rTMS relieved pain, associated anxiety and depression suggesting it as a valuable and safe new therapeutic option for FM patients.