Analgesic Effect of Cathodal tDCS Over Right DLPFC in Subjects With Muscular TMD: a Double Blind Crossover RCT

1. BACKGROUND: Temporomandibular Disorders (TMD) have become part of the daily routine of all the health care professionals. Some studies have shown improvement in subjects with chronic pain using neuromodulation. Chronic pain is involved with neuronal excitability and the excitatory modulation is also being studied to treat chronic pain. Transcranial direct current stimulation (tDCS) allows the neuronal membranes to be neuromodulated. tDCS can enhance or inhibit the potential actions on the cortex. Studies with animals has shown that anodal stimulation modulate the membrane in the way to depolarize which results in a long term potential in the stimulated area. 2. PROBLEM: Most strategies for the treatment of TMDs are local and aim to treat directly the cranial-facial muscles, applying kinesitherapy on Temporomandibular joint (TMJ) and/or on the jaws and on the occlusion of teeth. Some drugs, such as tricyclic antidepressants, that act in the CNS are used in these patients with positive results in the beginning of the treatment. However, many patients after using these drugs in a daily basis, are refractory to them and do not present an improvement in the pain anymore or present several side-effects. Therefore, the investigators want to know if tDCS over dorsolateral prefrontal cortex (DLPFC) would have an analgesic effect when reaching emotional areas. 3. HYPOTHESIS: The investigators believe that neuromodulation by tDCS over DLPFC would decrease the anxiety level and consequently the muscular hyperactivity that is an important etiological factor of TMD. For that, the masseter motor evoked potential (MEP) will be used to verify any change. 4. AIM: To investigate if cathodal tDCS over right DLPFC has analgesic effects in subjects with muscular TMD. 5. METHOD: The investigators will run a three-arm crossover double blind with 15 muscular TMD subjects. The group treatments will be cathodal tDCS 1mA, cathodal tDCS 2mA and Placebo. To verify selection criteria the inves