Repetitive Transcranial Magnetic Stimulation of the Left Premotor/Dorsolateral Prefrontal Cortex Does Not Have Analgesic Effect on Central Poststroke Pain

Strategies for replacing non-invasive brain stimulation sessions: recommendations for designing neurostimulation clinical trials

INTRODUCTION

Despite the potential impact of missed visits on the outcomes of neuromodulation treatments, it is not clear how this issue has been addressed in clinical trials. Given this gap in the literature, we reviewed articles on non-invasive brain stimulation in participants with depression or chronic pain, and investigated how missed visits were handled. Areas covered: We performed a search on PUBMED/MEDLINE using the keywords: 'tDCS', 'transcranial direct current stimulation', 'transcranial magnetic stimulation', 'depression', and 'pain'. We included studies with a minimum of five participants who were diagnosed with depression or chronic pain, who underwent a minimum of five tDCS or TMS sessions. A total of 181 studies matched our inclusion criteria, 112 on depression and 69 on chronic pain. Of these, only fifteen (8%) articles reported or had a protocol addressing missed visits. This review demonstrates that, in most of the trials, there is no reported plan to handle missed visits. Expert commentary: Based on our findings and previous studies, we developed suggestions on how to handle missed visits in neuromodulation protocols. A maximum of 20% of missing sessions should be allowed before excluding a patient and these sessions should be replaced at the end of the stimulation period.

Cortical neurostimulation for neuropathic pain: state of the art and perspectives

The treatment of neuropathic pain by neuromodulation is an objective for more than 40 years in modern clinical practice. With respect to spinal cord and deep brain structures, the cerebral cortex is the most recently evaluated target of invasive neuromodulation therapy for pain. In the early 90s, the first successes of invasive epidural motor cortex stimulation (EMCS) were published. A few years later was developed repetitive transcranial magnetic stimulation (rTMS), a noninvasive stimulation technique. Then, electrical transcranial stimulation returned valid and is currently in full development, with transcranial direct current stimulation (tDCS). Regarding transcranial approaches, the main studied and validated target was still the motor cortex, but other cortical targets are under investigation. The mechanisms of action of these techniques share similarities, especially between EMCS and rTMS, but they also have differences that could justify specific indications and applications. It is therefore important to know the principles and to assess the merit of these techniques on the basis of a rigorous assessment of the results, to avoid fad. Various types of chronic neuropathic pain syndromes can be significantly relieved by EMCS or repeated daily sessions of high-frequency (5-20 Hz) rTMS or anodal tDCS over weeks, at least when pain is lateralized and stimulation is applied to the motor cortex contralateral to pain side. However, cortical stimulation therapy remains to be optimized, especially by improving EMCS electrode design, rTMS targeting, or tDCS montage, to reduce the rate of nonresponders, who do not experience clinically relevant effects of these techniques.

EAN guidelines on central neurostimulation therapy in chronic pain conditions

BACKGROUND AND PURPOSE

Our aim was to update previous European Federation of Neurological Societies guidelines on neurostimulation for neuropathic pain, expanding the search to new techniques and to chronic pain conditions other than neuropathic pain, and assessing the evidence with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

METHODS

A systematic review and meta-analysis of trials published between 2006 and December 2014 was conducted. Pain conditions included neuropathic pain, fibromyalgia, complex regional pain syndrome (CRPS) type I and post-surgical chronic back and leg pain (CBLP). Spinal cord stimulation (SCS), deep brain stimulation (DBS), epidural motor cortex stimulation (MCS), repetitive transcranial magnetic stimulation (rTMS) and transcranial direct electrical stimulation (tDCS) of the primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC) were assessed. The GRADE system was used to assess quality of evidence and propose recommendations.

RESULTS

The following recommendations were reached: 'weak' for SCS added to conventional medical management in diabetic painful neuropathy, CBLP and CRPS, for SCS versus reoperation in CBLP, for MCS in neuropathic pain, for rTMS of M1 in neuropathic pain and fibromyalgia and for tDCS of M1 in neuropathic pain; 'inconclusive' for DBS in neuropathic pain, rTMS and tDCS of the DLPFC, and for motor cortex tDCS in fibromyalgia and spinal cord injury pain.

CONCLUSIONS

Given the poor to moderate quality of evidence identified by this review, future large-scale multicentre studies of non-invasive and invasive neurostimulation are encouraged. The collection of higher quality evidence of the predictive factors for the efficacy of these techniques, such as the duration, quality and severity of pain, is also recommended.

Effectiveness of repetitive trancranial or peripheral magnetic stimulation in neuropathic pain

PURPOSE

Maladaptive plasticity in the sensorimotor system, following neurological lesions or diseases, plays a central role in the generation and maintenance of neuropathic pain. Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief. Systematic reviews that evaluate the effectiveness and specificity of different protocols of repetitive magnetic stimulation to control neuropathic pain in clinical populations have the potential to improve the therapeutic applicability of this technique.

METHODS

Studies whose primary goal was to evaluate the effectiveness of repetitive magnetic stimulation for the treatment of various types of neuropathic pain published in PubMed until August 2015 have been included in this systematic review.

RESULTS

A total of 39 articles fulfilling the inclusion criteria were analyzed of which 37 studies investigated pain modulation using repetitive magnetic stimulation over the motor or non-motor cortices and two studies evaluated pain modulation using repetitive peripheral magnetic stimulation protocols.

CONCLUSIONS

Repetitive transcranial magnetic stimulation of the primary motor cortex using high frequency stimulation protocols can effectively reduce neuropathic pain, particularly in individuals with pain related to non-cerebral lesions. The application of multiple sessions can lead to long-lasting pain modulation and cumulative effects. Implications for Rehabilitation Maladaptive plasticity plays a central role in sensitization of nociceptive pathways, generation and maintainance of neuropathic pain; Most neuropathic pain conditions are refractory to pharmacological therapies; Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief.

Transcranial magnetic stimulation of the brain: guidelines for pain treatment research

Recognizing that electrically stimulating the motor cortex could relieve chronic pain sparked development of noninvasive technologies. In transcranial magnetic stimulation (TMS), electromagnetic coils held against the scalp influence underlying cortical firing. Multiday repetitive transcranial magnetic stimulation (rTMS) can induce long-lasting, potentially therapeutic brain plasticity. Nearby ferromagnetic or electronic implants are contraindications. Adverse effects are minimal, primarily headaches. Single provoked seizures are very rare. Transcranial magnetic stimulation devices are marketed for depression and migraine in the United States and for various indications elsewhere. Although multiple studies report that high-frequency rTMS of the motor cortex reduces neuropathic pain, their quality has been insufficient to support Food and Drug Administration application. Harvard's Radcliffe Institute therefore sponsored a workshop to solicit advice from experts in TMS, pain research, and clinical trials. They recommended that researchers standardize and document all TMS parameters and improve strategies for sham and double blinding. Subjects should have common well-characterized pain conditions amenable to motor cortex rTMS and studies should be adequately powered. They recommended standardized assessment tools (eg, NIH's PROMIS) plus validated condition-specific instruments and consensus-recommended metrics (eg, IMMPACT). Outcomes should include pain intensity and qualities, patient and clinician impression of change, and proportions achieving 30% and 50% pain relief. Secondary outcomes could include function, mood, sleep, and/or quality of life. Minimum required elements include sample sources, sizes, and demographics, recruitment methods, inclusion and exclusion criteria, baseline and posttreatment means and SD, adverse effects, safety concerns, discontinuations, and medication-usage records. Outcomes should be monitored for at least 3 months after initiation with prespecified statistical analyses. Multigroup collaborations or registry studies may be needed for pivotal trials.

The antalgic effects of non-invasive physical modalities on central post-stroke pain: a systematic review

[Purpose] This study systematically reviewed the antalgic effects of non-invasive physical modalities (NIPMs) on central post-stroke pain (CPSP). [Subjects and Methods] Clinical studies were sought on September 2015 in 10 electronic databases, including Medline and Scopus. The searching strings were “central pain and stroke” and “treatment, and physical or non-pharmacological”. The inclusion and exclusion criteria were set for screening the clinical articles by two reviewers. Pain scores on visual analog scale in an article were used as the outcome measure for resulting judgment. The NIPMs intervention summarized from the eligible articles was rated from Levels A to C according to Evidence Classification Scheme for Therapeutic Interventions. [Results] Over 1200 articles were identified in the initial searches and 85 studies were retrieved. Sixteen studies were eligible and judged. Caloric vestibular stimulation (n=3), heterotopic noxious conditioning stimulation (n=1), and transcutaneous electrical stimulation (n=1) were rated below Level C. Transcranial direct current stimulation (TDCS; n=2) and transcranial magnetic stimulation (TMS; n=9) were rated as Level B. [Conclusion] The findings suggest that TMS and TDCS were better than other treatments for CPSP relief but the studies were of insufficient quality.

Repetitive transcranial magnetic stimulation in chronic pain: a review of the literature

OBJECTIVE

To review the literature on the analgesic effects of repetitive transcranial magnetic stimulation (rTMS) in chronic pain according to different pain syndromes and stimulation parameters.

DATA SOURCES

Publications on rTMS and chronic pain were searched in PubMed and Google Scholar using the following key words: chronic pain, analgesia, transcranial magnetic stimulation, neuropathic pain, fibromyalgia, and complex regional pain syndrome.

STUDY SELECTION

This review only included double-blind, controlled studies with >10 participants in each arm that were published from 1996 to 2014 and written in English. Studies with relevant information for the understanding of the effects of rTMS were also cited.

DATA EXTRACTION

The following data were retained: type of pain syndrome, type of study, coil type, target, stimulation intensity, frequency, number of pulses, orientation of induced current, number of session, and a brief summary of intervention outcomes.

DATA SYNTHESIS

A total of 33 randomized trials were found. Many studies reported significant pain relief by rTMS, especially high-frequency stimulation over the primary motor cortex performed in consecutive treatment sessions. Pain relief was frequently >30% compared with control treatment. Neuropathic pain, fibromyalgia, and complex regional pain syndrome were the pain syndromes more frequently studied. However, among all published studies, only a few performed repetitive sessions of rTMS.

CONCLUSIONS

rTMS has potential utility in the management of chronic pain; however, studies using maintenance sessions of rTMS and assessing the effects of rTMS on the different aspects of chronic pain are needed to provide a more solid basis for its clinical application for pain relief.