Noninvasive transcranial brain stimulation in central post-stroke pain: A systematic review.

BACKGROUND: The aim of this systematic review is to analyze the efficacy of noninvasive brain stimulation (NBS) in the treatment of central post-stroke pain (CPSP). METHODS: We included randomized controlled trials testing the efficacy of transcranial magnetic stimulation (TMS) or transcranial direct current stimulation versus placebo or other usual therapy in patients with CPSP. Articles in English, Portuguese, Spanish, Italian, and French were included. A bibliographic search was independently conducted on June 1, 2022, by two authors, using the databases MEDLINE (PubMed), Embase (Elsevier), Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and Web of Science Core Collection. The risk of bias was assessed using the second version of the Cochrane risk of bias (RoB 2) tool and the certainty of the evidence was evaluated through Grading of Recommendations Assessment, Development and Evaluation. RESULTS: A total of 2,674 records were identified after removing duplicates, of which 5 eligible studies were included, involving a total of 119 patients. All five studies evaluated repetitive TMS, four of which stimulated the primary motor cortex (M1) and one stimulated the premotor/dorsolateral prefrontal cortex. Only the former one reported a significant pain reduction in the short term, while the latter one was interrupted due to a consistent lack of analgesic effect. CONCLUSION: NBS in the M1 area seems to be effective in reducing short-term pain; however, more high-quality homogeneous studies, with long-term follow-up, are required to determine the efficacy of this treatment in CSPS.

Comparison between two viscosupplementation protocols for temporomandibular joint osteoarthritis.

OBJECTIVE: This clinical trial aimed to compare the efficacy of two protocols using high molecular weight hyaluronic acid (HA) intra-articular injection in patients with temporomandibular joint (TMJ) osteoarthritis and evaluate involvement of subchondral bone changes and psychosocial factors as predictors of HA treatment. METHODS: Twenty-one individuals were divided into two groups: (A) received three intra-articular HA injections, and (B) received one injection. Outcomes observed were pain intensity, functional limitation, maximum voluntary mouth opening, maximum assisted mouth opening, and treatment tolerability. Follow-ups were performed weekly for 21 days, and two months after the treatment started. RESULTS: No statistically significant intergroup differences were observed in any of the evaluated outcomes. However, Group A showed significant improvement in all outcomes, whereas Group B showed significant improvement only in pain intensity and functional limitation. CONCLUSION: This study demonstrated the effectiveness of both protocols in terms of pain intensity and functional limitation caused by osteoarthritis.

The efficacy of transcranial direct current stimulation and transcranial magnetic stimulation for chronic orofacial pain: A systematic review.

BACKGROUND: Transcranial Direct Current Stimulation (tDCS) and Transcranial Magnetic Stimulation (TMS) have been described as promising alternatives to treat different pain syndromes. This study evaluated the effects of TMS and tDCS in the treatment of chronic orofacial pain, through a systematic review. METHODS: An electronic search was performed in major databases: MEDLINE, Scopus, Web of Science, Cochrane, Embase, LILACS, BBO, Open Gray and CINAHL. The eligibility criteria comprised randomized clinical trials (RCTs) that applied TMS or tDCS to treat chronic orofacial pain. The variables analyzed were pain, functional limitation, quality of life, tolerance to treatment, somatosensory changes, and adverse effects. The risk of bias was assessed through the Cochrane Collaboration tool, and the certainty of evidence was evaluated through GRADE. The protocol was registered in the PROSPERO database (CRD42018090774). RESULTS: The electronic search resulted in 636 studies. Thereafter, the eligibility criteria were applied and the duplicates removed, resulting in eight RCTs (four TMS and four tDCS). The findings of these studies suggest that rTMS applied to the Motor cortex (M1), the dorsolateral prefrontal cortex (DLPFC) and the secondary somatosensory cortex (S2) provide adequate orofacial pain relief. Two studies reported significant pain improvement with tDCS applied over M1 while the other two failed to demonstrate significant effects compared to placebo. CONCLUSIONS: rTMS, applied to M1, DLPFC or S2, is a promising approach for the treatment of chronic orofacial pain. Moreover, tDCS targeting M1 seems to be also effective in chronic orofacial pain treatment. The included studies used a wide variety of therapeutic protocols. In addition, most of them used small sample sizes, with a high risk of biases in their methodologies, thus producing a low quality of evidence. The results indicate that further research should be carried out with caution and with better-standardized therapeutic protocols.

The Contribution of Endogenous Modulatory Systems to TMS- and tDCS-Induced Analgesia: Evidence from PET Studies.

Chronic pain is an important public health issue. Moreover, its adequate management is still considered a major clinical problem, mainly due to its incredible complexity and still poorly understood pathophysiology. Recent scientific evidence coming from neuroimaging research, particularly functional magnetic resonance (fMRI) and positron emission tomography (PET) studies, indicates that chronic pain is associated with structural and functional changes in several brain structures that integrate antinociceptive pathways and endogenous modulatory systems. Furthermore, the last two decades have witnessed a huge increase in the number of studies evaluating the clinical effects of noninvasive neuromodulatory methods, especially transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), which have been proved to effectively modulate the cortical excitability, resulting in satisfactory analgesic effects with minimal adverse events. Nevertheless, the precise neuromechanisms whereby such methods provide pain control are still largely unexplored. Recent studies have brought valuable information regarding the recruitment of different modulatory systems and related neurotransmitters, including glutamate, dopamine, and endogenous opioids. However, the specific neurocircuits involved in the analgesia produced by those therapies have not been fully elucidated. This review focuses on the current literature correlating the clinical effects of noninvasive methods of brain stimulation to the changes in the activity of endogenous modulatory systems.