Fibromyalgia is a syndrome characterized by chronic generalized musculoskeletal pain, accompanied by other symptoms such as fatigue, sleep disturbance and depression. Complaints of memory deficit, cognitive dysfunction, headache and gastrointestinal disorders are also common. Although it is a relatively common syndrome, exist a limited effectiveness of the pharmacologycal treatment. However, In the last years new therapeutic and diagnostic options have been sought. This scenario includes the use of different techniques of non-invasive brain stimulation, such as transcranial direct current magnetic stimulation (tDCS) and transcranial magnetic stimulation (TMS), which have already had promising results in reducing pain. Based on the above, the objective of this research is to evaluate the effect of cerebellar tDCS on clinical measures of pain and cortical excitability in patients with fibromyalgia. In this study, the intervention consists of a single tDCS session in which two devices will be used simultaneously. The active electrode will be placed in the cerebellum and/or in the primary motor cortex and the cathode in the contralateral supraorbital region. It is expected that the application of this protocol will be able to have a modulatory effect on clinical pain measures. In addition to producing changes in cortical excitability as a reflection of the integration between the cerebellum-thalamus-cortical pathways.
The prevalence of fibromyalgia is approximately 2.7%, with a female-to-male ratio of 3:1. Although it is a relatively common syndrome, there are many doubts regarding its diagnosis and pathophysiology. In addition to the previously mentioned questions, this pathology has high social costs due to its association with the loss of labor productivity and it is characterized by being unresponsive to pharmacological treatment. Given the limited effectiveness of available therapeutic options, new therapeutic and diagnostic options have been sought. This scenario includes the use of different techniques of non-invasive brain stimulation, such as transcranial direct current magnetic stimulation (tDCS) and transcranial magnetic stimulation (TMS), which have already had promising results in reducing pain. In addition, TMS also allows measuring parameters that help to understand the reorganization of physiological processes. In this study, TMS is used to understand the pathophysiology of fibromyalgia, while tDCS allows modulating the excitability of the neuronal membrane potential of cortical and subcortical neural networks, producing a neuromodulatory effect of the top-down type. According to the evidence, the greatest impact on pain is associated with stimulation of the primary motor cortex (M1), but recent studies have shown the possible relationship between stimulation of extracerebral regions such as the cerebellum, with an analgesic effect present in healthy individuals and patients with different pathologies. In the same way, the cortical excitability measures obtained through TMS allow us to identify the imbalance between inhibitory and excitatory systems, related to pain perception and the analgesic response of endogenous mechanisms. In this research, our objective is to evaluate the effect of cerebellar tDCS on clinical measures of pain and cortical excitability in patients with fibromyalgia. This is a randomized, double-blind, controlled clinical trial, parallel, which has as its primary outcome, the evaluation of the variations in motor evoked potential (MEP) (neurophysiological outcome) and the numerical pain scale (NPS) as a clinical outcome. Secondary outcomes include the silent period (CSP), intra-cortical facilitation (ICF) and intra-cortical inhibition (ICI) obtained through TMS, the function of the descending modulatory path of pain by the conditioned modulation test (CPM test), the Brief Pain Inventory (BPI) and the pain thresholds by heat, pressure and cold. The intervention consists of a single tDCS session in which two devices will be used simultaneously. The active electrode will be placed in the cerebellum and/or in the primary motor cortex (4 stimulation protocols that will be implemented; active cerebellum electrode - active M1 electrode, sham cerebellum electrode - active M1 electrode, active cerebellum-M1 sham electrode, sham cerebellum electrode-M1 sham electrode) and the cathode in the contralateral supraorbital region. The equipment will apply a current of 2 mA for 20 minutes. In total, there will be 92 patients, divided into 4 intervention blocks and composed of 23 individuals each.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
92
Two tDCS devices will be used simultaneously. The intervention consists of a tDCS session in which the active electrode will be located in the cerebellum and/or in the primary motor cortex (4 stimulation protocols that will be implemented; active cerebellum electrode and active M1 electrode, sham cerebellum electrode and active M1 electrode, active cerebellum and sham M1 electrode, sham cerebellar electrode and sham M1 electrode) and the cathode in the contralateral supraorbital region.
Hospital de Clinicas de Porto Alegre
Porto Alegre, Rio Grande do Sul, Brazil
Hospital de clinicas de Porto Alegre
Porto Alegre, Rio Grande do Sul, Brazil
Change in motor evoked potential (MEP).
Change from before and after tDCS onset on MEP. Assessed by a variation in the amplitude obtained by 20 stimuli with an intensity of 120% of the MT. The MEP will be considered the arithmetic mean of the amplitude of the wave recorded by the EMG.
Time frame: Up to 60 minutes after tDCS onset.
Change in pain level
The study assessed the change in pain scores before and after tDCS onset using the Numerical Pain Scale (NPS). The NPS scores range from zero (no pain) to a maximum of ten (severe pain).
Time frame: Up to 60 minutes after tDCS onset.
Change in the Brief Pain Inventory (BPI) score
It is a quick, simple, and easy-to-apply questionnaire that allows a multidimensional pain assessment to be carried out. The BPI consists of 15 items that determine the severity, existence, location, functional interference, applied therapeutic strategies, and efficacy of pain treatment. In the research, this questionnaire will be implemented at baseline, 8 and 15 days after tDCS onset.
Time frame: Up to 15 days after tDCS onset.
Change in Function of corticospinal pathway
Measures of cortical excitability obtained through TMS include the silent period (CSP),intra-cortical facilitation (ICF) and intra-cortical inhibition (SICI). The TMS measures will be performed at two different times: before and after tDCS onset.
Time frame: Up to 60 minutes after tDCS onset.
change in conditioned pain modulation (CPM)
Conditioned pain modulation (CPM) is an experimental psychophysical measure that assesses supraspinal descending inhibitory mechanisms of pain modulation. In practice, a constant noxious stimulus (conditioning stimulus) is applied to one part of the body and a phasic stimulus (stimulus to be tested) to a distant part of the body before, during, and after the conditioning stimulus. The CPM is analyzed through the reduction that occurs in the perception of pain in the test stimulus.The conditioned pain modulation will be performed at two different times: before and after the single tDCS onset.
Time frame: Up to 60 minutes after tDCS onset.
Change in the quantitative sensory test (QST)
The quantitative sensory test (QST) evaluates the function of myelinated, small and unmyelinated fibers, also including the function of the spinothalamic tract and nociceptive fibers. In addition, the QST represents a non-invasive method, which determines the gain or loss of sensory perception in response to external stimuli of controlled intensity in a previously determined body area. The following tests will be carried out in the research: * Painful pressure threshold: performed with a pressure algometer, applied on the upper extremity. * Cold pressor test: the patient puts his extremity in a container with ice. The tolerance time will be determined. * Sensation of heat: using a heat electrode applied to the extremity corresponding to the sensitive alteration, the first sensation of heat and the painful threshold of light, medium and maximum heat will be evaluated. The QST measures will be performed at two different times; before and after the tDCS onset.
Time frame: Up to 60 minutes after tDCS onset.
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