Parameters and results of non-invasive neuromodulation in the management of chronic pelvic pain: integrative literature review / Parâmetros e resultados da neuromodulação não invasiva no manejo da dor pélvica crônica: revisão integrativa da literatura

ABSTRACT BACKGROUND AND OBJECTIVES: Chronic Pelvic Pain (CPP) is characterized by persistent pain in the pelvic region for more than six months, affecting both men and women and causing significant impairment in quality of life (QoL). Two of the main non-invasive approaches are Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS). These techniques aim to modulate neural activity and promote pain relief. In this context, this research conducted an integrative literature review to summarize the results of relevant studies, aiming to identify the key parameters used in TMS and tDCS for CPP treatment. The objective was to assess the effect and efficacy of non-invasive neuromodulation as a therapeutic intervention for CPP. CONTENTS: For this integrative review, electronic searches were conducted in Pubmed, Scielo, PEDro, Medline, Cochrane, and Scopus databases, examining studies in Portuguese, English, or Spanish. The keywords "pelvic pain," "transcranial direct current stimulation," and "transcranial magnetic stimulation" and their derivatives were searched in the three languages in studies from 2013 to 2023. Seven studies were included for analysis. Both techniques showed positive effects in managing CPP, improving pain levels and quality of life to a relevant extent. However, there is still no consensus on the parameters applied in TMS and tDCS techniques for CPP. CONCLUSION: Non-invasive neuromodulation improves pain levels and quality of life in patients with CPP. Further studies are needed to establish more reliable parameter relationships, and the limited number of studies restricts definitive conclusions on the subject.

RESUMO JUSTIFICATIVA E OBJETIVOS: A dor pélvica crônica (DPC) é caracterizada pela persistência da dor na região pélvica por mais de seis meses, afetando tanto homens quanto mulheres e causando prejuízos significativos na qualidade de vida (QV). Duas das principais abordagens não invasivas são Estimulação Magnética Transcraniana (EMT) e a Estimulação Transcraniana por Corrente Contínua (ETCC). Nesse contexto, esta pesquisa realizou uma revisão integrativa da literatura com o intuito de resumir os resultados de estudos relevantes, buscando identificar os principais parâmetros utilizados no tratamento da DPC. O objetivo foi fornecer uma visão abrangente sobre essas técnicas de neuromodulação e suas aplicações específicas no controle da dor pélvica crônica. CONTEÚDO: Para esta revisão integrativa, as buscas eletrônicas ocorreram nas bases de dados Pubmed, Scielo, PEDro, Medline, Cochrane e Scopus, verificando estudos em português, inglês ou espanhol. "Dor pélvica", "estimulação transcraniana por corrente contínua" e "estimulação magnética transcraniana" e suas derivações foram pesquisadas nos três idiomas em estudos entre 2013 e 2023. Sete estudos foram incluídos para análise. Ambas as técnicas apresentaram efeitos positivos no manejo da DPC, melhorando os níveis de dor e a QV em proporções relevantes. Entretanto, ainda não há um consenso sobre os parâmetros aplicados nas técnicas de EMT e ETCC para DPC. CONCLUSÃO: A neuromodulação não invasiva melhora os níveis de dor e a QV em pacientes com DPC. São necessários mais estudos para que relações mais confiáveis de parâmetros possam ser preestabelecidas e a ausência de um maior número de estudos limita conclusões acerca do assunto.

Mapping the modulating effect of transcutaneous auricular vagus nerve stimulation on voxel-based analyses in patients with first-episode major depressive disorder: a resting-state functional magnetic resonance imaging study.

INTRODUCTION: Seed-based analysis has shown that transcutaneous auricular vagus nerve stimulation (taVNS) can modulate the dysfunctional brain network in patients with major depressive disorder (MDD). However, the voxel-based neuropsychological mechanism of taVNS on patients with first-episode MDD is poorly understood. The objective of this study was to assess the effects of an 8-week course of taVNS on patients with first-episode MDD. METHODS: Twenty-two patients with first-episode MDD accepted an 8-week course of taVNS treatment. Resting-state functional magnetic resonance imaging (rs-fMRI) scans were performed before and after treatment. Voxel-based analyses were performed to characterize spontaneous brain activity. Healthy controls (n=23) were recruited to minimize test-retest effects. Analysis of covariance (ANCOVA) was performed to ascertain treatment-related changes. Then, correlations between changes in brain activity and the Hamilton Depression Rating Scale (HAM-D)/Hamilton Anxiety Scale (HAM-A) remission rate were estimated. RESULTS: Significant group-by-time interactions on voxel-based analyses were observed in the inferior ventral striatum (VSi) and precuneus. Post-hoc analyses showed that taVNS inhibited higher brain activity in the VSi, while upregulating it in the precuneus. Functional connectivity (FC) between the VSi and precuneus decreased. Positive correlations were found between the HAM-D remission rate and changes in brain activity in the VSi. CONCLUSION: taVNS reduced the FC between VSi and precuneus by normalizing the abnormal spontaneous brain activity of VSi in first-episode MDD patients.

Mapping the modulating effect of transcutaneous auricular vagus nerve stimulation on voxel-based analyses in patients with first-episode major depressive disorder: a resting-state functional magnetic resonance imaging study

Introduction: Seed-based analysis has shown that transcutaneous auricular vagus nerve stimulation (taVNS) can modulate the dysfunctional brain network in patients with major depressive disorder (MDD). However, the voxel-based neuropsychological mechanism of taVNS on patients with first-episode MDD is poorly understood. The objective of this study was to assess the effects of an 8-week course of taVNS on patients with first-episode MDD. Methods: Twenty-two patients with first-episode MDD accepted an 8-week course of taVNS treatment. Resting-state functional magnetic resonance imaging (rs-fMRI) scans were performed before and after treatment. Voxel-based analyses were performed to characterize spontaneous brain activity. Healthy controls (n=23) were recruited to minimize test-retest effects. Analysis of covariance (ANCOVA) was performed to ascertain treatment-related changes. Then, correlations between changes in brain activity and the Hamilton Depression Rating Scale (HAM-D)/Hamilton Anxiety Scale (HAM-A) remission rate were estimated. Results: Significant group-by-time interactions on voxel-based analyses were observed in the inferior ventral striatum (VSi) and precuneus. Post-hoc analyses showed that taVNS inhibited higher brain activity in the VSi, while upregulating it in the precuneus. Functional connectivity (FC) between the VSi and precuneus decreased. Positive correlations were found between the HAM-D remission rate and changes in brain activity in the VSi. Conclusion: taVNS reduced the FC between VSi and precuneus by normalizing the abnormal spontaneous brain activity of VSi in first-episode MDD patients.

Case Report: Galvanic Vestibular Stimulation in the Chronic Spinal Cord Injury Patient.

The traumatic spinal cord injury can generate sequels with high clinical severity and dysfunction and limitations of irreversible character. Current studies seek to reverse the sequelae and gain functionality in these individuals. Galvanic vestibular stimulation (GVS) has shown to be beneficial in spinal cord function as an evaluation correlated to functionality and for stimulation with physiological and functional characteristics in disease and healthy people. The present study observed the effects of Noise Galvanic Vestibular Stimulation in a patient with chronic spinal cord injury with tetraplegia on postural and trunk control. The evaluations were the Functional Independence Measure (FIM), the American Spinal Injury Association (ASIA) evaluation, and the Clinical Posturography, using force platform to assess postural balance, in the sitting position, through Sensory Organization and Functional Reach Tests. Ten sessions of Noise Galvanic Vestibular Stimulation associated with customized vestibular and neurofunctional rehabilitation were performed. The effects observed were increments in all assessments and tests that include modifications in functional independence, motor and sensory levels, change in disability grade from A (complete) to C (incomplete), and improvements in postural balance and trunk control. The phenomenon of stochastic resonance has shown benefits in postural control in people without vestibular lesions and we could observe some of these phenomena in our patients. We emphasize the need for evaluation with larger populations to observe the phenomena and effects in this group of patients and potential benefits and limitations.

Transcranial Electrical Neuromodulation Based on the Reciprocity Principle.

A key challenge in multi-electrode transcranial electrical stimulation (TES) or transcranial direct current stimulation (tDCS) is to find a current injection pattern that delivers the necessary current density at a target and minimizes it in the rest of the head, which is mathematically modeled as an optimization problem. Such an optimization with the Least Squares (LS) or Linearly Constrained Minimum Variance (LCMV) algorithms is generally computationally expensive and requires multiple independent current sources. Based on the reciprocity principle in electroencephalography (EEG) and TES, it could be possible to find the optimal TES patterns quickly whenever the solution of the forward EEG problem is available for a brain region of interest. Here, we investigate the reciprocity principle as a guideline for finding optimal current injection patterns in TES that comply with safety constraints. We define four different trial cortical targets in a detailed seven-tissue finite element head model, and analyze the performance of the reciprocity family of TES methods in terms of electrode density, targeting error, focality, intensity, and directionality using the LS and LCMV solutions as the reference standards. It is found that the reciprocity algorithms show good performance comparable to the LCMV and LS solutions. Comparing the 128 and 256 electrode cases, we found that use of greater electrode density improves focality, directionality, and intensity parameters. The results show that reciprocity principle can be used to quickly determine optimal current injection patterns in TES and help to simplify TES protocols that are consistent with hardware and software availability and with safety constraints.

Novel neurotherapeutics in psychiatry: use and rationale of transcranial direct current stimulation in major depressive disorder / Novas neuroterapêuticas em psiquiatria: racional e uso da estimulação transcraniana por corrente contínua no transtorno depressivo maior

Background: Transcranial direct current stimulation (tDCS) is a novel non-pharmacological intervention being investigated for the treatment of major depressive disorder (MDD). Objective: To perform an updated review of tDCS for MDD. Method: Systematic review in Medline/PubMed and other databases of all clinical studies evaluating the clinical efficacy of tDCS in MDD, from the first date available to December/2013. Results: Out of 55 articles, 24 were included, being 6 open-label studies; 8 randomized, double-blind, sham-controlled trials; 2 follow-up studies; 2 meta-analyses and 6 case reports. We observed an improvement of 20-40% in depressive symptoms, being slightly better in open studies. Five randomized clinical trials displayed positive results. The meta-analyses presented mixed results; although none included the study of Brunoni et al. (2013) that represents almost 50% of the evaluated sample. Open-label studies and case reports also investigated tDCS in bipolar depression, post-stroke depression and employed different parameters of stimulation. Discussion: TDCS is a novel, promising treatment for MDD. Definite evidence from large, ongoing clinical trials will be available in the next years...

Contexto: A estimulação transcraniana por corrente contínua (ETCC) é uma nova intervenção não farmacológica investigada como tratamento no transtorno depressivo maior (TDM). Objetivo: Apresentar uma revisão atualizada da ETCC no TDM. Método: Revisão sistemática no banco de dados Medline/PubMed e outros de todos os estudos clínicos publicados avaliando a eficácia da ETCC no TDM, da primeira data disponível a dezembro/2013. Resultados : De 55 artigos, 24 foram incluídos, sendo 6 estudos abertos; 8 ensaios clínicos randomizados, duplo-cego, placebo controlados; 2 estudos de seguimento; 2 metanálises e 6 relatos de caso. Observa-se uma melhora de 20-40% nos sintomas depressivos, sendo ligeiramente maior nos estudos abertos. Entre os ensaios controlados, 5 demonstraram eficácia da técnica. As metanálises divergiram quanto aos resultados, mostrando presença e ausência de eficácia e ausência da ETCC. Porém, nenhuma incluiu o estudo de Brunoni et al. (2013), que representa quase 50% da população estudada. Estudos abertos e relatos de caso também investigaram o uso da ETCC na depressão bipolar, na depressão pós-AVC e usaram variações nos parâmetros de estimulação. Conclusões: A ETCC é uma técnica promissora no tratamento da TDM. Evidências definitivas devem estar disponíveis nos próximos anos, com a divulgação de resultados de grandes ensaios clínicos em andamento...