Effect of Noninvasive Neuromodulation on Chronic Pain

1. BACKGROUND: Temporomandibular Dysfunction (TMD) is a disease characterized by a set of signs and symptoms that may include joint noise, pain in the mastication muscles, limitation of mandibular movements, facial pain, joint pain and / or dental wear. Pain appears as a very present and striking symptom, with a tendency to chronicity. This is a difficult treatment condition often associated with psychological factors such as anxiety. Chronic pain involved modifications in the neuronal excitability, therefore, the neuromodulation withTranscranial direct current stimulation (tDCS) appears as a possible strategy for the treatment. Some studies have shown improvement in subjects with chronic pain using tDCS, however, it needs further investigation of its therapeutic effect.
2. PROBLEM: Despite the wide range of strategies used to treat patients with TMD, some patients have a temporary and / or unsatisfactory relief response, which generates hypotheses that emotional components often underlie treatment refractoriness, and development of a memory for pain. Thus, it is evident the need for a therapy that acts directly on the central nervous system (CNS). This action can occur through medications, however, many individuals are refractory or have side effects such as dependence and / or tolerance. In this way, the importance of new treatments involving neuromodulation and neuroplasticity mechanisms, such as tDCS, is highlighted, which may become a complementary alternative to the different types of treatment already in use. Besides corroborating with the need to give preference to reversible and non-invasive procedures.
3. HYPOTHESIS: The investigators believe that the use of anodic tDCS in the treatment of patients with TMD presenting with chronic pain will have a positive effect, promoting a decrease in painful symptoms through a Central Nervous System (neuromodulation) action in comparison to placebo stimulation. Because of the mutual influence between pain and psychological factors, it is expected that the analgesic effect will have a positive effect on anxiety levels. In addition, it is believed that a more intense analgesic effect occurs in the DLPF stimulation group of the cortex compared to the M1 stimulation group, since this region demonstrates to be responsible for the processing of the emotional component of the pain, often underlying the refractoriness to treatment
4. AIM: To evaluate and compare the efficacy of anodic tDCS, applied in different cortical regions (M1 and DLPFC), in the pain and anxiety levels in individuals with chronic pain due muscular TMD.


Eligibility Criteria:
Inclusion Criteria:

* Age between 18-60 years, both male and female
* Provide informed consent to participate in the study;
* Having a diagnosis of muscular pain DTM according to IA and IB, axis I RDC/TMD
* Visual analogic scale (VAS) score from 4 to 10 for six months or longer
* Presence of moderate depressive symptoms through SCL-90 scale evaluation of Axis II, (RDC / TMD)
* Not pregnant;
* Not have contraindications to tDCS, such as metal implants on the head or implanted brain devices;
* Not have history of alcohol or drugs abuse within the past 6 months as self-reported
* Not use of carbamazepine within the past 6 months as self reported
* Not have any history of epilepsy, stroke, moderate-to-severe traumatic brain injury or severe migraines
* Not have history of neurosurgery as self-reported
* Not have history of major psychiatric disorders such as schizophrenia and bipolar disorder
* Not have any other previously diagnosed disorder with symptoms similar to the DTM, such as fibromyalgia.

Exclusion Criteria:

* Two absences during treatment sessions;
* During the research, go against some criteria of inclusion mentioned above, as in the case of women, getting pregnant.