Efficacy of Transcranial Magnetic Stimulation (TMS) in Chronic Idiopathic Pain Disorders

Several lines of evidence suggest that fibromyalgia syndrome, Irritable Bowel syndrome (IBS) and burning mouth syndrome are chronic pain disorders affecting pain modulation. Repetitive transcranial magnetic stimulation (rTMS) is a recent, safe and non-invasive technique for stimulating the cerebral cortex, which has recently been reported to induce short term analgesic effects in patients with chronic focal pain. We have also recently shown in a double blind randomized trial, that rTMS could have short term analgesic effects in patients with fibromyalgia.

Objectives : Our aim is to investigate the long term analgesic effects of repeated sessions of unilateral rTMS in patients with chronic pain syndrome due to fibromyalgia, IBS or burning mouth syndrome. Primary outcome will be numerical pain scores on brief pain inventory at each visit.

Methods : This study will be randomized and performed in parallel groups and double blind versus sham stimulation. It will include at least 30 patients per pain disorder, ie 90 patients. Randomization will be computerized and performed for each of the aetiological groups separately (ie, there will be 3 distinct randomization procedures for fibromyalgia, IBS and stomatodynia);. Stimulation will be applied to the right motor area corresponding to the contralateral hand. The treatment will consist in a first period of 5 consecutive days of stimulation, followed by a stimulation once a week during 3 weeks then a stimulation twice a month during 2 months then stimulation once a month during 3 additional months. Clinical assessment will be performed at baseline, then at day 1, 5, weeks 3, 5, 7, 9, 13 and 25. It will include depending on the visits an assessment of pain intensity and characteristics, quality of life, sleep, depression and anxiety, catastrophizing, and a brief neuropsychological evaluation (focusing on memory, attention and vigilance). In patients with fibromyalgia, the evaluation will also include specifically the number of tender points. In patients with IBS, evaluation of bowel dysfunction will also be performed.

Conclusion : This study should allow to determine for the first time the long term efficacy and safety of rTMS in the treatment of dysfunctional or idiopathic chronic pain syndromes which are often refractory to conventional treatments.

Inclusion criteria

• Pain related to Fibromyalgia (ACR criteria) or IBS (Rome II criteria) or burning mouth syndrome (IHS criteria 2004)
• Chronic pain for at least 6 months
• Pain for at least 4 days a week
• Mean average pain score at inclusion and randomization ≥ 4/10 (numerical scale)
• Patients aged 18 years and less than 80 years
• Informed consent
• Stable antalgic treatment

Exclusion criteria

• Contraindications to TMS (electroconvulsive therapy, epilepsy, head trauma, intracranial hypertension, metallic clip, pace maker, pregnancy)
• Major depression (DSM IV criteria) or psychosis
• Disorder preventing an accurate understanding of the testing and protocol
• Intermittent pain
• Pain for less than 6 months
• Other pain more severe than the pain evaluated for the trial
• Alcohol/psychoactive drugs abuse