Transcranial magnetic stimulation—a sandwich coil design for a better sham

Placebo effects of repetitive transcranial magnetic stimulation on negative symptoms and cognition in patients with schizophrenia spectrum disorders: a systematic review and meta-analysis

Background

Negative symptoms and cognitive impairments are highly frequent in schizophrenia spectrum disorders (SSD), associated with adverse functional outcomes and quality of life. Repetitive transcranial magnetic stimulation (rTMS) has been considered a promising therapeutic option in SSD. However, placebo effects of rTMS on these symptoms remained unclear.

Objective

To investigate placebo effects of rTMS on alleviating negative symptoms and cognitive impairment in patients with SSD and to explore potential moderators.

Methods

We systematically searched five electronic databases up to 15 July 2023. Randomized, double-blind, sham-controlled trials investigating effects of rTMS on negative symptoms or cognition in patients with SSD were included. The pooled placebo effect sizes, represented by Hedges' g, were estimated using the random-effects model. Potential moderators were explored through subgroup analysis and meta-regression.

Results

Forty-four randomized controlled trials with 961 patients (mean age 37.53 years; 28.1% female) in the sham group were included. Significant low-to-moderate pooled placebo effect sizes were observed for negative symptoms (g=0.44, p<0.001), memory (g=0.31, p=0.010), executive function (g=0.35, p<0.001), working memory (g=0.26, p=0.004), and processing speed (g=0.36, p=0.004). Subgroup analysis indicated that placebo effects were affected by sham stimulation methods, rTMS targeting approaches, and stimulation frequency.

Conclusions

Placebo effects of rTMS on negative symptoms and cognition in patients with SSD are significant in a small-to-moderate magnitude, which might be mediated by rTMS parameters. Our findings will provide new insights for practitioners to further optimize and establish standardized rTMS protocols for future RCTs tackling cardinal symptoms in SSD.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023390138.

Devices and Technology in Transcranial Magnetic Stimulation: A Systematic Review

The technology for transcranial magnetic stimulation (TMS) has significantly changed over the years, with important improvements in the signal generators, the coils, the positioning systems, and the software for modeling, optimization, and therapy planning. In this systematic literature review (SLR), the evolution of each component of TMS technology is presented and analyzed to assess the limitations to overcome. This SLR was carried out following the PRISMA 2020 statement. Published articles of TMS were searched for in four databases (Web of Science, PubMed, Scopus, IEEE). Conference papers and other reviews were excluded. Records were filtered using terms about TMS technology with a semi-automatic software; articles that did not present new technology developments were excluded manually. After this screening, 101 records were included, with 19 articles proposing new stimulator designs (18.8%), 46 presenting or adapting coils (45.5%), 18 proposing systems for coil placement (17.8%), and 43 implementing algorithms for coil optimization (42.6%). The articles were blindly classified by the authors to reduce the risk of bias. However, our results could have been influenced by our research interests, which would affect conclusions for applications in psychiatric and neurological diseases. Our analysis indicates that more emphasis should be placed on optimizing the current technology with a special focus on the experimental validation of models. With this review, we expect to establish the base for future TMS technological developments.

Control interventions in randomised trials among people with mental health disorders

BACKGROUND

Control interventions in randomised trials provide a frame of reference for the experimental interventions and enable estimations of causality. In the case of randomised trials assessing patients with mental health disorders, many different control interventions are used, and the choice of control intervention may have considerable impact on the estimated effects of the treatments being evaluated.

OBJECTIVES

To assess the benefits and harms of typical control interventions in randomised trials with patients with mental health disorders. The difference in effects between control interventions translates directly to the impact a control group has on the estimated effect of an experimental intervention. We aimed primarily to assess the difference in effects between (i) wait-list versus no-treatment, (ii) usual care versus wait-list or no-treatment, and (iii) placebo interventions (all placebo interventions combined or psychological, pharmacological, and physical placebos individually) versus wait-list or no-treatment. Wait-list patients are offered the experimental intervention by the researchers after the trial has been finalised if it offers more benefits than harms, while no-treatment participants are not offered the experimental intervention by the researchers.

SEARCH METHODS

In March 2018, we searched MEDLINE, PsycInfo, Embase, CENTRAL, and seven other databases and six trials registers.

SELECTION CRITERIA

We included randomised trials assessing patients with a mental health disorder that compared wait-list, usual care, or placebo interventions with wait-list or no-treatment .

DATA COLLECTION AND ANALYSIS

Titles, abstracts, and full texts were reviewed for eligibility. Review authors independently extracted data and assessed risk of bias using Cochrane's risk of bias tool. GRADE was used to assess the quality of the evidence. We contacted researchers working in the field to ask for data from additional published and unpublished trials. A pre-planned decision hierarchy was used to select one benefit and one harm outcome from each trial. For the assessment of benefits, we summarised continuous data as standardised mean differences (SMDs) and dichotomous data as risk ratios (RRs). We used risk differences (RDs) for the assessment of adverse events. We used random-effects models for all statistical analyses. We used subgroup analysis to explore potential causes for heterogeneity (e.g. type of placebo) and sensitivity analyses to explore the robustness of the primary analyses (e.g. fixed-effect model).

MAIN RESULTS

We included 96 randomised trials (4200 participants), ranging from 8 to 393 participants in each trial. 83 trials (3614 participants) provided usable data. The trials included 15 different mental health disorders, the most common being anxiety (25 trials), depression (16 trials), and sleep-wake disorders (11 trials). All 96 trials were assessed as high risk of bias partly because of the inability to blind participants and personnel in trials with two control interventions. The quality of evidence was rated low to very low, mostly due to risk of bias, imprecision in estimates, and heterogeneity. Only one trial compared wait-list versus no-treatment directly but the authors were not able to provide us with any usable data on the comparison. Five trials compared usual care versus wait-list or no-treatment and found a SMD -0.33 (95% CI -0.83 to 0.16, I² = 86%, 523 participants) on benefits. The difference between all placebo interventions combined versus wait-list or no-treatment was SMD -0.37 (95% CI -0.49 to -0.25, I² = 41%, 65 trials, 2446 participants) on benefits. There was evidence of some asymmetry in the funnel plot (Egger's test P value of 0.087). Almost all the trials were small. Subgroup analysis found a moderate effect in favour of psychological placebos SMD -0.49 (95% CI -0.64 to -0.30; I² = 53%, 39 trials, 1656 participants). The effect of pharmacological placebos versus wait-list or no-treatment on benefits was SMD -0.14 (95% CI -0.39 to 0.11, 9 trials, 279 participants) and the effect of physical placebos was SMD -0.21 (95% CI -0.35 to -0.08, I² = 0%, 17 trials, 896 participants). We found large variations in effect sizes in the psychological and pharmacological placebo comparisons. For specific mental health disorders, we found significant differences in favour of all placebos for sleep-wake disorders, major depressive disorder, and anxiety disorders, but the analyses were imprecise due to sparse data. We found no significant differences in harms for any of the comparisons but the analyses suffered from sparse data. When using a fixed-effect model in a sensitivity analysis on the comparison for usual care versus wait-list and no-treatment, the results were significant with an SMD of -0.46 (95 % CI -0.64 to -0.28). We reported an alternative risk of bias model where we excluded the blinding domains seeing how issues with blinding may be seen as part of the review investigation itself. However, this did not markedly change the overall risk of bias profile as most of the trials still included one or more unclear bias domains.

AUTHORS' CONCLUSIONS

We found marked variations in effects between placebo versus no-treatment and wait-list and between subtypes of placebo with the same comparisons. Almost all the trials were small with considerable methodological and clinical variability in factors such as mental health population, contents of the included control interventions, and outcome domains. All trials were assessed as high risk of bias and the evidence quality was low to very low. When researchers decide to use placebos or usual care control interventions in trials with people with mental health disorders it will often lead to lower estimated effects of the experimental intervention than when using wait-list or no-treatment controls. The choice of a control intervention therefore has considerable impact on how effective a mental health treatment appears to be. Methodological guideline development is needed to reach a consensus on future standards for the design and reporting of control interventions in mental health intervention research.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane Review published in 2010, Issue 9, and last updated in 2014, Issue 4. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive cortical stimulation techniques in the treatment of chronic pain.

SEARCH METHODS

For this update we searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, LILACS and clinical trials registers from July 2013 to October 2017.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS, RINCE and tRNS if they employed a sham stimulation control group, recruited patients over the age of 18 years with pain of three months' duration or more, and measured pain as an outcome. Outcomes of interest were pain intensity measured using visual analogue scales or numerical rating scales, disability, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and verified data. Where possible we entered data into meta-analyses, excluding studies judged as high risk of bias. We used the GRADE system to assess the quality of evidence for core comparisons, and created three 'Summary of findings' tables.

MAIN RESULTS

We included an additional 38 trials (involving 1225 randomised participants) in this update, making a total of 94 trials in the review (involving 2983 randomised participants). This update included a total of 42 rTMS studies, 11 CES, 36 tDCS, two RINCE and two tRNS. One study evaluated both rTMS and tDCS. We judged only four studies as low risk of bias across all key criteria. Using the GRADE criteria we judged the quality of evidence for each outcome, and for all comparisons as low or very low; in large part this was due to issues of blinding and of precision.rTMSMeta-analysis of rTMS studies versus sham for pain intensity at short-term follow-up (0 to < 1 week postintervention), (27 studies, involving 655 participants), demonstrated a small effect with heterogeneity (standardised mean difference (SMD) -0.22, 95% confidence interval (CI) -0.29 to -0.16, low-quality evidence). This equates to a 7% (95% CI 5% to 9%) reduction in pain, or a 0.40 (95% CI 0.53 to 0.32) point reduction on a 0 to 10 pain intensity scale, which does not meet the minimum clinically important difference threshold of 15% or greater. Pre-specified subgroup analyses did not find a difference between low-frequency stimulation (low-quality evidence) and rTMS applied to the prefrontal cortex compared to sham for reducing pain intensity at short-term follow-up (very low-quality evidence). High-frequency stimulation of the motor cortex in single-dose studies was associated with a small short-term reduction in pain intensity at short-term follow-up (low-quality evidence, pooled n = 249, SMD -0.38 95% CI -0.49 to -0.27). This equates to a 12% (95% CI 9% to 16%) reduction in pain, or a 0.77 (95% CI 0.55 to 0.99) point change on a 0 to 10 pain intensity scale, which does not achieve the minimum clinically important difference threshold of 15% or greater. The results from multiple-dose studies were heterogeneous and there was no evidence of an effect in this subgroup (very low-quality evidence). We did not find evidence that rTMS improved disability. Meta-analysis of studies of rTMS versus sham for quality of life (measured using the Fibromyalgia Impact Questionnaire (FIQ) at short-term follow-up demonstrated a positive effect (MD -10.80 95% CI -15.04 to -6.55, low-quality evidence).CESFor CES (five studies, 270 participants) we found no evidence of a difference between active stimulation and sham (SMD -0.24, 95% CI -0.48 to 0.01, low-quality evidence) for pain intensity. We found no evidence relating to the effectiveness of CES on disability. One study (36 participants) of CES versus sham for quality of life (measured using the FIQ) at short-term follow-up demonstrated a positive effect (MD -25.05 95% CI -37.82 to -12.28, very low-quality evidence).tDCSAnalysis of tDCS studies (27 studies, 747 participants) showed heterogeneity and a difference between active and sham stimulation (SMD -0.43 95% CI -0.63 to -0.22, very low-quality evidence) for pain intensity. This equates to a reduction of 0.82 (95% CI 0.42 to 1.2) points, or a percentage change of 17% (95% CI 9% to 25%) of the control group outcome. This point estimate meets our threshold for a minimum clinically important difference, though the lower confidence interval is substantially below that threshold. We found evidence of small study bias in the tDCS analyses. We did not find evidence that tDCS improved disability. Meta-analysis of studies of tDCS versus sham for quality of life (measured using different scales across studies) at short-term follow-up demonstrated a positive effect (SMD 0.66 95% CI 0.21 to 1.11, low-quality evidence).Adverse eventsAll forms of non-invasive brain stimulation and sham stimulation appear to be frequently associated with minor or transient side effects and there were two reported incidences of seizure, both related to the active rTMS intervention in the included studies. However many studies did not adequately report adverse events.

AUTHORS' CONCLUSIONS

There is very low-quality evidence that single doses of high-frequency rTMS of the motor cortex and tDCS may have short-term effects on chronic pain and quality of life but multiple sources of bias exist that may have influenced the observed effects. We did not find evidence that low-frequency rTMS, rTMS applied to the dorsolateral prefrontal cortex and CES are effective for reducing pain intensity in chronic pain. The broad conclusions of this review have not changed substantially for this update. There remains a need for substantially larger, rigorously designed studies, particularly of longer courses of stimulation. Future evidence may substantially impact upon the presented results.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane Review published in 2010, Issue 9, and last updated in 2014, Issue 4. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive cortical stimulation techniques in the treatment of chronic pain.

SEARCH METHODS

For this update we searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, LILACS and clinical trials registers from July 2013 to October 2017.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS, RINCE and tRNS if they employed a sham stimulation control group, recruited patients over the age of 18 years with pain of three months' duration or more, and measured pain as an outcome. Outcomes of interest were pain intensity measured using visual analogue scales or numerical rating scales, disability, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and verified data. Where possible we entered data into meta-analyses, excluding studies judged as high risk of bias. We used the GRADE system to assess the quality of evidence for core comparisons, and created three 'Summary of findings' tables.

MAIN RESULTS

We included an additional 38 trials (involving 1225 randomised participants) in this update, making a total of 94 trials in the review (involving 2983 randomised participants). This update included a total of 42 rTMS studies, 11 CES, 36 tDCS, two RINCE and two tRNS. One study evaluated both rTMS and tDCS. We judged only four studies as low risk of bias across all key criteria. Using the GRADE criteria we judged the quality of evidence for each outcome, and for all comparisons as low or very low; in large part this was due to issues of blinding and of precision.rTMSMeta-analysis of rTMS studies versus sham for pain intensity at short-term follow-up (0 to < 1 week postintervention), (27 studies, involving 655 participants), demonstrated a small effect with heterogeneity (standardised mean difference (SMD) -0.22, 95% confidence interval (CI) -0.29 to -0.16, low-quality evidence). This equates to a 7% (95% CI 5% to 9%) reduction in pain, or a 0.40 (95% CI 0.53 to 0.32) point reduction on a 0 to 10 pain intensity scale, which does not meet the minimum clinically important difference threshold of 15% or greater. Pre-specified subgroup analyses did not find a difference between low-frequency stimulation (low-quality evidence) and rTMS applied to the prefrontal cortex compared to sham for reducing pain intensity at short-term follow-up (very low-quality evidence). High-frequency stimulation of the motor cortex in single-dose studies was associated with a small short-term reduction in pain intensity at short-term follow-up (low-quality evidence, pooled n = 249, SMD -0.38 95% CI -0.49 to -0.27). This equates to a 12% (95% CI 9% to 16%) reduction in pain, or a 0.77 (95% CI 0.55 to 0.99) point change on a 0 to 10 pain intensity scale, which does not achieve the minimum clinically important difference threshold of 15% or greater. The results from multiple-dose studies were heterogeneous and there was no evidence of an effect in this subgroup (very low-quality evidence). We did not find evidence that rTMS improved disability. Meta-analysis of studies of rTMS versus sham for quality of life (measured using the Fibromyalgia Impact Questionnaire (FIQ) at short-term follow-up demonstrated a positive effect (MD -10.80 95% CI -15.04 to -6.55, low-quality evidence).CESFor CES (five studies, 270 participants) we found no evidence of a difference between active stimulation and sham (SMD -0.24, 95% CI -0.48 to 0.01, low-quality evidence) for pain intensity. We found no evidence relating to the effectiveness of CES on disability. One study (36 participants) of CES versus sham for quality of life (measured using the FIQ) at short-term follow-up demonstrated a positive effect (MD -25.05 95% CI -37.82 to -12.28, very low-quality evidence).tDCSAnalysis of tDCS studies (27 studies, 747 participants) showed heterogeneity and a difference between active and sham stimulation (SMD -0.43 95% CI -0.63 to -0.22, very low-quality evidence) for pain intensity. This equates to a reduction of 0.82 (95% CI 0.42 to 1.2) points, or a percentage change of 17% (95% CI 9% to 25%) of the control group outcome. This point estimate meets our threshold for a minimum clinically important difference, though the lower confidence interval is substantially below that threshold. We found evidence of small study bias in the tDCS analyses. We did not find evidence that tDCS improved disability. Meta-analysis of studies of tDCS versus sham for quality of life (measured using different scales across studies) at short-term follow-up demonstrated a positive effect (SMD 0.66 95% CI 0.21 to 1.11, low-quality evidence).Adverse eventsAll forms of non-invasive brain stimulation and sham stimulation appear to be frequently associated with minor or transient side effects and there were two reported incidences of seizure, both related to the active rTMS intervention in the included studies. However many studies did not adequately report adverse events.

AUTHORS' CONCLUSIONS

There is very low-quality evidence that single doses of high-frequency rTMS of the motor cortex and tDCS may have short-term effects on chronic pain and quality of life but multiple sources of bias exist that may have influenced the observed effects. We did not find evidence that low-frequency rTMS, rTMS applied to the dorsolateral prefrontal cortex and CES are effective for reducing pain intensity in chronic pain. The broad conclusions of this review have not changed substantially for this update. There remains a need for substantially larger, rigorously designed studies, particularly of longer courses of stimulation. Future evidence may substantially impact upon the presented results.

TMS SMART - Scalp mapping of annoyance ratings and twitches caused by Transcranial Magnetic Stimulation

BACKGROUND

The magnetic pulse generated during transcranial magnetic stimulation (TMS) also stimulates cutaneous nerves and muscle fibres, with the most commonly reported side effect being muscle twitches and sometimes painful sensations. These sensations affect behaviour during experimental tasks, presenting a potential confound for 'online' TMS studies.

NEW METHOD

Our objective was to systematically map the degree of disturbance (ratings of annoyance, pain, and muscle twitches) caused by TMS at 43 locations across the scalp. Ten participants provided ratings whilst completing a choice reaction time task, and ten different participants provided ratings whilst completing a 'flanker' reaction time task.

RESULTS

TMS over frontal and inferior regions resulted in the highest ratings of annoyance, pain, and muscle twitches caused by TMS. We predicted the difference in reaction times (RT) under TMS by scalp location and subjective ratings. Frontal and inferior scalp locations showed the greatest cost to RTs under TMS (i.e., slowing), with midline sites showing no or minimal slowing. Increases in subjective ratings of disturbance predicted longer RTs under TMS. Critically, ratings were a better predictor of the cost of TMS than scalp location or scalp-to-cortex distance. The more difficult 'flanker' task showed a greater effect of subjective disturbance.

COMPARISON WITH EXISTING METHODS

We provide the data as an online resource (www.tms-smart.info) so that researchers can select control sites that account for the level of general interference in task performance caused by online single-pulse TMS.

CONCLUSIONS

The peripheral sensations and discomfort caused by TMS pulses significantly and systematically influence RTs during single-pulse, online TMS experiments.

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

Dystonias represent a heterogeneous group of movement disorders responsible for sustained muscle contraction, abnormal postures, and muscle twists. It can affect focal or segmental body parts or be generalized. Primary dystonia is the most common form of dystonia but it can also be secondary to metabolic or structural dysfunction, the consequence of a drug's side-effect or of genetic origin. The pathophysiology is still not elucidated. Based on lesion studies, dystonia has been regarded as a pure motor dysfunction of the basal ganglia loop. However, basal ganglia lesions do not consistently produce dystonia and lesions outside basal ganglia can lead to dystonia; mild sensory abnormalities have been reported in the dystonic limb and imaging studies have shown involvement of multiple other brain regions including the cerebellum and the cerebral motor, premotor and sensorimotor cortices. Transcranial magnetic stimulation (TMS) is a non-invasive technique of brain stimulation with a magnetic field applied over the cortex allowing investigation of cortical excitability. Hyperexcitability of contralateral motor cortex has been suggested to be the trigger of focal dystonia. High or low frequency repetitive TMS (rTMS) can induce excitatory or inhibitory lasting effects beyond the time of stimulation and protocols have been developed having either a positive or a negative effect on cortical excitability and associated with prevention of cell death, γ-aminobutyric acid (GABA) interneurons mediated inhibition and brain-derived neurotrophic factor modulation. rTMS studies as a therapeutic strategy of dystonia have been conducted to modulate the cerebral areas involved in the disease. Especially, when applied on the contralateral (pre)-motor cortex or supplementary motor area of brains of small cohorts of dystonic patients, rTMS has shown a beneficial transient clinical effect in association with restrained motor cortex excitability. TMS is currently a valuable tool to improve our understanding of the pathophysiology of dystonia but large controlled studies using sham stimulation are still necessary to delineate the place of rTMS in the therapeutic strategy of dystonia. In this review, we will focus successively on the use of TMS as a tool to better understand pathophysiology, and the use of rTMS as a therapeutic strategy.

Pulse Width Affects Scalp Sensation of Transcranial Magnetic Stimulation

BACKGROUND

Scalp sensation and pain comprise the most common side effect of transcranial magnetic stimulation (TMS), which can reduce tolerability and complicate experimental blinding.

OBJECTIVE

We explored whether changing the width of single TMS pulses affects the quality and tolerability of the resultant somatic sensation.

METHODS

Using a controllable pulse parameter TMS device with a figure-8 coil, single monophasic magnetic pulses inducing electric field with initial phase width of 30, 60, and 120 µs were delivered in 23 healthy volunteers. Resting motor threshold of the right first dorsal interosseus was determined for each pulse width, as reported previously. Subsequently, pulses were delivered over the left dorsolateral prefrontal cortex at each of the three pulse widths at two amplitudes (100% and 120% of the pulse-width-specific motor threshold), with 20 repetitions per condition delivered in random order. After each pulse, subjects rated 0-to-10 visual analog scales for Discomfort, Sharpness, and Strength of the sensation.

RESULTS

Briefer TMS pulses with amplitude normalized to the motor threshold were perceived as slightly more uncomfortable than longer pulses (with an average 0.89 point increase on the Discomfort scale for pulse width of 30 µs compared to 120 µs). The sensation of the briefer pulses was felt to be substantially sharper (2.95 points increase for 30 µs compared to 120 µs pulse width), but not stronger than longer pulses. As expected, higher amplitude pulses increased the perceived discomfort and strength, and, to a lesser degree the perceived sharpness.

CONCLUSIONS

Our findings contradict a previously published hypothesis that briefer TMS pulses are more tolerable. We discovered that the opposite is true, which merits further study as a means of enhancing tolerability in the context of repetitive TMS.

Theta burst stimulation over the supplementary motor area in Parkinson's disease

To investigate whether a period of continuous theta burst stimulation (cTBS) over the supplementary motor area (SMA) induces cortical plasticity and thus improves bradykinesia in Parkinson's disease (PD) in the medication ON and OFF state. In total, 26 patients with Parkinson's disease were tested with both real and sham stimulation. The group was divided into an OFF-medication (4 females, mean age 65 years, disease duration 6 years) and an ON-medication group (7 females, mean age 61 years, disease duration 7 years) with each containing 13 individuals. Both groups were evaluated in terms of electrophysiological (motor-evoked potentials) and behavioural [Purdue Pegboard test (PPT), UPDRS motor subscore] parameters before (baseline condition) and after a 40-second period of real or sham continuous theta burst stimulation over the SMA ON and OFF dopaminergic drugs. Patients in the OFF group demonstrated an improved UPDRS III score (p < 0.05) and a better performance in the PPT for the less affected side (p < 0.025) compared to baseline after real stimulation. However, electrophysiological parameters did not change in either the ON or the OFF state. cTBS over the SMA has a mild effect on motor symptoms of the upper limb in the OFF state of PD patients. In contrast, stimulation did not change cortico-spinal excitability. A lack of change (i.e. no plasticity) to brain stimulation protocols is a known finding in PD. A clinical improvement in the OFF state, however, contrasts with this and the mechanism of these induced changes is worth further exploration.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane review published in 2010, Issue 9. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive brain stimulation techniques in chronic pain.

SEARCH METHODS

We searched CENTRAL (2013, Issue 6), MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS and clinical trials registers. The original search for the review was run in November 2009 and searched all databases from their inception. To identify studies for inclusion in this update we searched from 2009 to July 2013.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS or RINCE if they employed a sham stimulation control group, recruited patients over the age of 18 with pain of three months duration or more and measured pain as a primary outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted and verified data. Where possible we entered data into meta-analyses. We excluded studies judged as being at high risk of bias from the analysis. We used the GRADE system to summarise the quality of evidence for core comparisons.

MAIN RESULTS

We included an additional 23 trials (involving 773 participants randomised) in this update, making a total of 56 trials in the review (involving 1710 participants randomised). This update included a total of 30 rTMS studies, 11 CES, 14 tDCS and one study of RINCE(the original review included 19 rTMS, eight CES and six tDCS studies). We judged only three studies as being at low risk of bias across all criteria.Meta-analysis of studies of rTMS (involving 528 participants) demonstrated significant heterogeneity. Pre-specified subgroup analyses suggest that low-frequency stimulation is ineffective (low-quality evidence) and that rTMS applied to the dorsolateral prefrontal cortex is ineffective (very low-quality evidence). We found a short-term effect on pain of active high-frequency stimulation of the motor cortex in single-dose studies (low-quality evidence, standardised mean difference (SMD) 0.39 (95% confidence interval (CI) -0.27 to -0.51 P < 0.01)). This equates to a 12% (95% CI 8% to 15%) reduction in pain, which does not exceed the pre-established criteria for a minimal clinically important difference (≥ 15%). Evidence for multiple-dose studies was heterogenous but did not demonstrate a significant effect (very low-quality evidence).For CES (six studies, 270 participants) no statistically significant difference was found between active stimulation and sham (low-quality evidence).Analysis of tDCS studies (11 studies, 193 people) demonstrated significant heterogeneity and did not find a significant difference between active and sham stimulation (very low-quality evidence). Pre-specified subgroup analysis of tDCS applied to the motor cortex (n = 183) did not demonstrate a statistically significant effect and this lack of effect was consistent for subgroups of single or multiple-dose studies.One small study (n = 91) at unclear risk of bias suggested a positive effect of RINCE over sham stimulation on pain (very low-quality evidence).Non-invasive brain stimulation appears to be frequently associated with minor and transient side effects, though there were two reported incidences of seizure related to active rTMS in the included studies.

AUTHORS' CONCLUSIONS

Single doses of high-frequency rTMS of the motor cortex may have small short-term effects on chronic pain. It is likely that multiple sources of bias may exaggerate this observed effect. The effects do not meet the predetermined threshold of minimal clinical significance and multiple-dose studies do not consistently demonstrate effectiveness. The available evidence suggests that low-frequency rTMS, rTMS applied to the pre-frontal cortex, CES and tDCS are not effective in the treatment of chronic pain. While the broad conclusions for rTMS and CES have not changed substantially, the addition of this new evidence and the application of the GRADE system has modified some of our interpretation and the conclusion regarding the effectiveness of tDCS has changed. We recommend that previous readers should re-read this update. There is a need for larger, rigorously designed studies, particularly of longer courses of stimulation. It is likely that future evidence may substantially impact upon the presented results.

Far-space neglect in conjunction but not feature search following transcranial magnetic stimulation over right posterior parietal cortex

Near- and far-space coding in the human brain is a dynamic process. Areas in dorsal, as well as ventral visual association cortex, including right posterior parietal cortex (rPPC), right frontal eye field (rFEF), and right ventral occipital cortex (rVO), have been shown to be important in visuospatial processing, but the involvement of these areas when the information is in near or far space remains unclear. There is a need for investigations of these representations to help explain the pathophysiology of hemispatial neglect, and the role of near and far space is crucial to this. We used a conjunction visual search task using an elliptical array to investigate the effects of transcranial magnetic stimulation delivered over rFEF, rPPC, and rVO on the processing of targets in near and far space and at a range of horizontal eccentricities. As in previous studies, we found that rVO was involved in far-space search, and rFEF was involved regardless of the distance to the array. It was found that rPPC was involved in search only in far space, with a neglect-like effect when the target was located in the most eccentric locations. No effects were seen for any site for a feature search task. As the search arrays had higher predictability with respect to target location than is often the case, these data may form a basis for clarifying both the role of PPC in visual search and its contribution to neglect, as well as the importance of near and far space in these.

Blinding integrity in randomized sham-controlled trials of repetitive transcranial magnetic stimulation for major depression: a systematic review and meta-analysis

Repetitive transcranial magnetic stimulation (rTMS) is a safe and effective treatment for major depression (MD). However, the perceived lack of a suitable sham rTMS condition might have compromised the success of blinding procedures in clinical trials. Thus, we conducted a systematic review and meta-analysis of randomized, double-blind and sham-controlled trials (RCTs) on high frequency (HF-), low frequency (LF-) and bilateral rTMS for MD. We searched the literature from January 1995 to July 2012 using Medline, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials and Scopus. The main outcome measure was participants' ability to correctly guess their treatment allocation at study end. We used a random-effects model and risk difference (RD). Overall, data were obtained from seven and two RCTs on HF- and bilateral rTMS, respectively. No RCT on LF-rTMS reporting on blinding success was found. HF- and bilateral rTMS trials enrolled 396 and 93 depressed subjects and offered an average of approximately 13 sessions. At study end, 52 and 59% of subjects receiving HF-rTMS and sham rTMS were able to correctly guess their treatment allocation, a non-significant difference (RD = -0.04; z = -0.51; p = 0.61). Furthermore, 63.3 and 57.5% of subjects receiving bilateral and sham rTMS were able to correctly guess their treatment allocation, also a non-significant difference (RD = 0.05; z = 0.49; p = 0.62). In addition, the use of angulation and sham coil in HF-rTMS trials produced similar results. In summary, existing sham rTMS interventions appear to result in acceptable levels of blinding regarding treatment allocation.

Blinding success of rTMS applied to the dorsolateral prefrontal cortex in randomised sham-controlled trials: a systematic review

OBJECTIVES

The lack of a suitable sham condition for repetitive transcranial magnetic stimulation (rTMS) research may compromise the success of blinding procedures. The aim of this systematic review was to examine the reporting of blinding success in randomised sham-controlled trials (RCTs) of rTMS applied to the dorsolateral prefrontal cortex.

METHODS

A literature search using Pubmed and Web of Science was conducted to identify RCTs of rTMS. Regression analyses were used to investigate whether participants in the real and sham rTMS groups differed in (1) their ability to correctly guess to which intervention they had been randomised, and (2) how likely they were to think they had received real rTMS.

RESULTS

Thirteen out of 96 (13.5%) RCTs reported blinding success. Available data from 9/13 studies showed that participants in real and sham rTMS groups were not significantly different in their ability to correctly guess their intervention allocation, but with a trend for participants in the real group to more often guess correctly. However, people in the real rTMS groups were significantly more likely to think they had received real rTMS compared with those in sham rTMS groups.

CONCLUSIONS

Few RCTs in rTMS report on blinding success. As current sham methods may inadequately mimic real rTMS, this could result in only partial success of blinding and bias estimations of treatment effects.

[Transcranial magnetic stimulation (TMS) in basic and clinical neuroscience research]

INTRODUCTION

Non-invasive brain stimulation methods such as transcranial magnetic stimulation (TMS) are starting to be widely used to make causality-based inferences about brain-behavior interactions. Moreover, TMS-based clinical applications are under development to treat specific neurological or psychiatric conditions, such as depression, dystonia, pain, tinnitus and the sequels of stroke, among others.

BACKGROUND

TMS works by inducing non-invasively electric currents in localized cortical regions thus modulating their activity levels according to settings, such as frequency, number of pulses, train and regime duration and intertrain intervals. For instance, it is known for the motor cortex that low frequency or continuous patterns of TMS pulses tend to depress local activity whereas high frequency and discontinuous TMS patterns tend to enhance it. Additionally, local cortical effects of TMS can result in dramatic patterns in distant brain regions. These distant effects are mediated via anatomical connectivity in a magnitude that depends on the efficiency and sign of such connections.

PERSPECTIVES

An efficient use of TMS in both fields requires however, a deep understanding of its operational principles, its risks, its potential and limitations. In this article, we will briefly present the principles through which non-invasive brain stimulation methods, and in particular TMS, operate.

CONCLUSION

Readers will be provided with fundamental information needed to critically discuss TMS studies and design hypothesis-driven TMS applications for cognitive and clinical neuroscience research.

Transcranial magnetic stimulation coil with electronically switchable active and sham modes

Blinded studies with transcranial magnetic stimulation (TMS) require a valid sham condition. A wide range of sham approaches have been implemented but they have various limitations including residual electric field in the brain, inadequate reproduction of auditory and cutaneous sensations, and/or need for electrical stimulation with scalp electrodes. We propose a quadrupole TMS coil configuration that can be electronically switched between active and sham modes. In active mode, the quadrupole coil has electric field characteristics similar to a conventional figure-8 coil. In sham mode, the quadrupole coil compared to the reverse-current sham figure-8 coil has 50% less electric field penetration depth, is 97% more focal, produces 35% less intense field in the brain, and induces scalp electric field characteristics closer to those of active TMS.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES) and transcranial direct current stimulation (tDCS).

OBJECTIVES

To evaluate the efficacy of non-invasive brain stimulation techniques in chronic pain.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS, the Cochrane PaPaS Group Trials Register and clinical trials registers.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES or tDCS if they employed a sham stimulation control group, recruited patients over the age of 18 with pain of three months duration or more and measured pain as a primary outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted and verified data. Where possible we entered data into meta-analyses. We excluded studies judged as being at high risk of bias from the analysis.

MAIN RESULTS

We included 33 trials in the review (involving 937 people)(19 rTMS, eight CES and six tDCS). Only one study was judged as being at low risk of bias.Studies of rTMS (involving 368 participants ) demonstrated significant heterogeneity. Pre-specified subgroup analyses suggest that low-frequency stimulation is ineffective. A short-term effect on pain of active high-frequency stimulation of the motor cortex in single-dose studies was suggested (standardised mean difference (SMD) -0.40, 95% confidence interval (CI) -0.26 to -0.54, P < 0.00001). This equates to a 15% (95% CI 10% to 20%) reduction in pain which does not clearly exceed the pre-established criteria for a minimally clinically important difference (> 15%).For CES (four studies, 133 participants) no statistically significant difference was found between active stimulation and sham. Analysis of tDCS studies (five studies, 83 people) demonstrated significant heterogeneity and did not find a significant difference between active and sham stimulation. Pre-specified subgroup analysis of tDCS applied to the motor cortex suggested superiority of active stimulation over sham (SMD -0.59, 95% CI -1.10 to -0.08).Non-invasive brain stimulation appears to be associated with minor and transient side effects.

AUTHORS' CONCLUSIONS

Single doses of high-frequency rTMS of the motor cortex may have small short-term effects on chronic pain. The effects do not clearly exceed the predetermined threshold of minimal clinical significance. Low-frequency rTMS is not effective in the treatment of chronic pain. There is insufficient evidence from which to draw firm conclusions regarding the efficacy of CES or tDCS. The available evidence suggests that tDCS applied to the motor cortex may have short-term effects on chronic pain and that CES may be ineffective. There is a need for further, rigorously designed studies of all types of stimulation.

Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research

This article is based on a consensus conference, which took place in Certosa di Pontignano, Siena (Italy) on March 7-9, 2008, intended to update the previous safety guidelines for the application of transcranial magnetic stimulation (TMS) in research and clinical settings. Over the past decade the scientific and medical community has had the opportunity to evaluate the safety record of research studies and clinical applications of TMS and repetitive TMS (rTMS). In these years the number of applications of conventional TMS has grown impressively, new paradigms of stimulation have been developed (e.g., patterned repetitive TMS) and technical advances have led to new device designs and to the real-time integration of TMS with electroencephalography (EEG), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Thousands of healthy subjects and patients with various neurological and psychiatric diseases have undergone TMS allowing a better assessment of relative risks. The occurrence of seizures (i.e., the most serious TMS-related acute adverse effect) has been extremely rare, with most of the few new cases receiving rTMS exceeding previous guidelines, often in patients under treatment with drugs which potentially lower the seizure threshold. The present updated guidelines review issues of risk and safety of conventional TMS protocols, address the undesired effects and risks of emerging TMS interventions, the applications of TMS in patients with implanted electrodes in the central nervous system, and safety aspects of TMS in neuroimaging environments. We cover recommended limits of stimulation parameters and other important precautions, monitoring of subjects, expertise of the rTMS team, and ethical issues. While all the recommendations here are expert based, they utilize published data to the extent possible.

Sham Transcranial Magnetic Stimulation Using Electrical Stimulation of the Scalp

BACKGROUND: Most methods of sham, repetitive transcranial magnetic stimulation (rTMS) fail to replicate the look, sound, and feel of active stimulation in the absence of a significant magnetic field. OBJECTIVE/HYPOTHESIS: To develop and validate a new method of sham rTMS appropriate for a double-blind, placebo-controlled study with subject crossover. METHODS: The look and sound of active rTMS was replicated using a matched, air-cooled sham TMS coil. Scalp muscle stimulation associated with rTMS was replicated using large rubber electrodes placed over selected muscles. The intensity and pulse width of electrical stimulation necessary to match 1-Hz rTMS was developed in one sample of normal subjects. The sham technique was validated in back-to-back comparisons with active rTMS in new samples of normal subjects who were either naïve or experienced with rTMS. RESULTS: Subjects naïve to TMS could not tell which type of stimulation was active or sham or which was electrical or magnetic. Naïve subjects incorrectly picked sham stimulation as active, when forced to choose, because electrical stimulation felt more focused than magnetic stimulation. Subjects experienced with TMS could correctly identify sham and active stimulation. Experimenters could detect subtle differences between conditions. CONCLUSIONS: This method of sham rTMS closely mimics the look, sound, and feel of active stimulation at 1Hz without creating a significant magnetic field. It is valid for use with naïve subjects and in crossover studies. It can accommodate differences in scalp muscle recruitment at different sites of stimulation, and it could potentially be used with higher frequency stimulation.

Assessment of verbal memory by fMRI: lateralization and functional neuroanatomy

OBJECTIVES

The medial temporal lobe (MTL) is essential for declarative memory formation, but also a frequent source of seizures. To decrease the risk of amnestic impairments after temporal lobectomy, functional magnetic resonance imaging (fMRI) is increasingly used to establish pre-operative measures for a prognosis of postoperative memory performance. The present study addresses one of the major challenges in clinical fMRI, the interpretation of activation pattern in single subjects. Before investigating patients however, it must be first assessed to which extent the verbal memory paradigm can be used to determine the lateralization and the functional neuroanatomy of MTL-activity. Therefore, this study took a "step backwards" by first examining healthy subjects without known MTL pathology.

PATIENTS AND METHODS

An implicit verbal encoding task was applied to a group of ten healthy volunteers using fMRI.

RESULTS

At the group level the MTL activation was strongly left-lateralized and separated into three distinct clusters. At the individual level, the lateralization of MTL-activity could be determined in 9 of 10 subjects. In contrast, its localization was inter-individually highly variable. In each case, only one of the three group activation clusters was detected.

CONCLUSIONS

The present study shows that fMRI can be used to assess the lateralization of brain activity related to verbal encoding even in individual subjects. For the routine use in a clinical setting however, the results of verbal memory paradigms must at present be treated with care if they are used to support decisions as to how far the resection of one MTL can be extended.

Controversy: Does repetitive transcranial magnetic stimulation/ transcranial direct current stimulation show efficacy in treating tinnitus patients?

BACKGROUND

Tinnitus affects 10% of the population, its pathophysiology remains incompletely understood, and treatment is elusive. Functional imaging has demonstrated a relationship between the intensity of tinnitus and the degree of reorganization in the auditory cortex. Experimental studies have further shown that tinnitus is associated with synchronized hyperactivity in the auditory cortex. Therefore, targeted modulation of auditory cortex has been proposed as a new therapeutic approach for chronic tinnitus.

METHODS

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are noninvasive methods that can modulate cortical activity. These techniques have been applied in different ways in patients with chronic tinnitus. Single sessions of high-frequency rTMS over the temporal cortex have been successful in reducing the intensity of tinnitus during the time of stimulation and could be predictive for treatment outcome of chronic epidural stimulation using implanted electrodes.

RESULTS

Another approach that uses rTMS as a treatment for tinnitus is application of low-frequency rTMS in repeated sessions, to induce a lasting change of neuronal activity in the auditory cortex beyond the duration of stimulation. Beneficial effects of this treatment have been consistently demonstrated in several small controlled studies. However, results are characterized by high interindividual variability and only a moderate decrease of the tinnitus. The role of patient-related (for example, hearing loss, tinnitus duration, age) and stimulation-related (for example, stimulation site, stimulation protocols) factors still remains to be elucidated.

CONCLUSIONS

Even in this early stage of investigation, there is a convincing body of evidence that rTMS represents a promising tool for pathophysiological assessment and therapeutic management of tinnitus. Further development of this technique will depend on a more detailed understanding of the neurobiological effects mediating the benefit of TMS on tinnitus perception. Moreover clinical studies with larger sample sizes and longer follow-up periods are needed.

A real electro-magnetic placebo (REMP) device for sham transcranial magnetic stimulation (TMS)

OBJECTIVE

There is growing interest in neuropsychiatry for repetitive transcranial magnetic stimulation (rTMS) as a neuromodulatory treatment. However, there are limitations in interpreting rTMS effects as a real consequence of physiological brain changes or as placebo-mediated unspecific effects, which may be particularly strong in psychiatric patients. This is due to the fact that existing sham rTMS procedures are less than optimal. A new placebo tool is introduced here, called real electro-magnetic placebo (REMP) device, which can simulate the scalp sensation induced by the real TMS, while leaving both the visual impact and acoustic sensation of real TMS unaltered.

METHODS

Physical, neurophysiological and behavioural variables of monophasic and biphasic single-pulse TMS and biphasic 1Hz and 20Hz rTMS procedures (at different intensities) were tested in subjects who were expert or naïve of TMS. Results of the real TMS were compared with those induced by the REMP device and with two other currently used sham procedures, namely the commercially available Magstim sham coil and tilting the real coil by 90 degrees .

RESULTS

The REMP device, besides producing scalp sensations similar to the real TMS, attenuated the TMS-induced electric field (as measured by a dipole probe) to a biologically inactive level. Behaviourally, neither expert nor naïve TMS subjects identified the "coil at 90 degrees " or the "Magstim sham coil" as a real TMS intervention, whilst naïve subjects were significantly more likely to identify the REMP-attenuated TMS as real.

CONCLUSIONS

The "goodness of sham" of the REMP device is demonstrated by physical, neurophysiological, and behavioural results.

SIGNIFICANCE

Such placebo TMS is superior to the available sham procedures when applied on subjects naïve to TMS, as in case of patients undergoing a clinical rTMS trial.