Multiday Transcranial Direct Current Stimulation Causes Clinically Insignificant Changes in Childhood Dystonia: A Pilot Study

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Effects of non-invasive brain stimulation in dystonia: a systematic review and meta-analysis

Background

Deep brain stimulation is a highly effective treatment of dystonia but is invasive and associated with risks, such as intraoperative bleeding and infections. Previous research has used non-invasive brain stimulation (NIBS) in an attempt to alleviate symptoms of dystonia. The results of these studies, however, have been variable, leaving efficacy unclear.

Objectives

This study aimed to evaluate the effects of NIBS on symptoms of dystonia and determine whether methodological characteristics are associated with variability in effect size.

Methods

Web of Science, Embase, and MEDLINE Complete databases were searched for articles using any type of NIBS as an intervention in dystonia patients, with changes in dystonia symptoms the primary outcome of interest.

Results

Meta-analysis of 27 studies demonstrated a small effect size for NIBS in reducing symptoms of dystonia (random-effects Hedges' g = 0.21, p = .002). Differences in the type of NIBS, type of dystonia, and brain region stimulated had a significant effect on dystonia symptoms. Meta-regression revealed that 10 sessions of active stimulation and the application of concurrent motor training programs resulted in significantly larger mean effect sizes.

Conclusion

NIBS has yielded small improvements to dystonic symptoms, but effect sizes depended on methodological characteristics, with more sessions of stimulation producing a larger response. Future research should further investigate the application of NIBS parallel to motor training, in addition to providing a greater quantity of sessions, to help define optimal parameters for NIBS protocols in dystonia.

Registration

PROSPERO 2020, CRD42020175944.

Neurophysiological Basis of Deep Brain Stimulation and Botulinum Neurotoxin Injection for Treating Oromandibular Dystonia

Oromandibular dystonia (OMD) induces severe motor impairments, such as masticatory disturbances, dysphagia, and dysarthria, resulting in a serious decline in quality of life. Non-invasive brain-imaging techniques such as electroencephalography (EEG) and magnetoencephalography (MEG) are powerful approaches that can elucidate human cortical activity with high temporal resolution. Previous studies with EEG and MEG have revealed that movements in the stomatognathic system are regulated by the bilateral central cortex. Recently, in addition to the standard therapy of botulinum neurotoxin (BoNT) injection into the affected muscles, bilateral deep brain stimulation (DBS) has been applied for the treatment of OMD. However, some patients' OMD symptoms do not improve sufficiently after DBS, and they require additional BoNT therapy. In this review, we provide an overview of the unique central spatiotemporal processing mechanisms in these regions in the bilateral cortex using EEG and MEG, as they relate to the sensorimotor functions of the stomatognathic system. Increased knowledge regarding the neurophysiological underpinnings of the stomatognathic system will improve our understanding of OMD and other movement disorders, as well as aid the development of potential novel approaches such as combination treatment with BoNT injection and DBS or non-invasive cortical current stimulation therapies.

Instrumented assessment of motor function in dyskinetic cerebral palsy: a systematic review

BACKGROUND

In this systematic review we investigate which instrumented measurements are available to assess motor impairments, related activity limitations and participation restrictions in children and young adults with dyskinetic cerebral palsy. We aim to classify these instrumented measurements using the categories of the international classification of functioning, disability and health for children and youth (ICF-CY) and provide an overview of the outcome parameters.

METHODS

A systematic literature search was performed in November 2019. We electronically searched Pubmed, Embase and Scopus databases. Search blocks included (a) cerebral palsy, (b) athetosis, dystonia and/or dyskinesia, (c) age 2-24 years and (d) instrumented measurements (using keywords such as biomechanics, sensors, smartphone, and robot).

RESULTS

Our search yielded 4537 articles. After inspection of titles and abstracts, a full text of 245 of those articles were included and assessed for further eligibility. A total of 49 articles met our inclusion criteria. A broad spectrum of instruments and technologies are used to assess motor function in dyskinetic cerebral palsy, with the majority using 3D motion capture and surface electromyography. Only for a small number of instruments methodological quality was assessed, with only one study showing an adequate assessment of test-retest reliability. The majority of studies was at ICF-CY function and structure level and assessed control of voluntary movement (29 of 49) mainly in the upper extremity, followed by assessment of involuntary movements (15 of 49), muscle tone/motor reflex (6 of 49), gait pattern (5 of 49) and muscle power (2 of 49). At ICF-CY level of activities and participation hand and arm use (9 of 49), fine hand use (5 of 49), lifting and carrying objects (3 of 49), maintaining a body position (2 of 49), walking (1 of 49) and moving around using equipment (1 of 49) was assessed. Only a few methods are potentially suitable outside the clinical environment (e.g. inertial sensors, accelerometers).

CONCLUSION

Although the current review shows the potential of several instrumented methods to be used as objective outcome measures in dyskinetic cerebral palsy, their methodological quality is still unknown. Future development should focus on evaluating clinimetrics, including validating against clinical meaningfulness. New technological developments should aim for measurements that can be applied outside the laboratory.

Transcranial Direct Current Stimulation in Pediatric Motor Disorders: A Systematic Review and Meta-analysis

OBJECTIVE

To systematically examine the safety and effectiveness of transcranial direct current stimulation (tDCS) interventions in pediatric motor disorders.

DATA SOURCES

PubMed, EMBASE, Cochrane, CINAHL, Web of Science, and ProQuest databases were searched from inception to August 2018.

STUDY SELECTION

tDCS randomized controlled trials (RCTs), observational studies, conference proceedings, and dissertations in pediatric motor disorders were included. Two authors independently screened articles based on predefined inclusion criteria.

DATA EXTRACTION

Data related to participant demographics, intervention, and outcomes were extracted by 2 authors. Quality assessment was independently performed by 2 authors.

DATA SYNTHESIS

A total of 23 studies involving a total of 391 participants were included. There was no difference in dropout rates between active (1 of 144) and sham (1 of 144) tDCS groups, risk difference 0.0, 95% confidence interval (-.05 to .04). Across studies, the most common adverse effects in the active group were tingling (17.2%), discomfort (8.02%), itching (6.79%), and skin redness (4%). Across 3 studies in children with cerebral palsy, tDCS significantly improved gait velocity (MD=.23; 95% confidence interval [0.13-0.34]; P<.0005), stride length (MD=0.10; 95% confidence interval [0.05-0.15]; P<.0005), and cadence (MD=15.7; 95% confidence interval [9.72-21.68]; P<.0005). Mixed effects were found on balance, upper extremity function, and overflow movements in dystonia.

CONCLUSION

Based on the studies reviewed, tDCS is a safe technique in pediatric motor disorders and may improve some gait measures and involuntary movements. Research to date in pediatric motor disorders shows limited effectiveness in improving balance and upper extremity function. tDCS may serve as a potential adjunct to pediatric rehabilitation; to better understand if tDCS is beneficial for pediatric motor disorders, more well-designed RCTs are needed.

Impact of Transcranial Direct Current Stimulation on Reading Skills of Children and Adolescents With Dyslexia

Introduction:

Rehabilitation techniques have been used to facilitate reading acquisition in dyslexia. However, many individuals continue to present academic impairment throughout life. New intervention strategies are necessary to further help this population.

Objectives:

Assess the impact of transcranial direct current stimulation on reading skills in children and adolescents with dyslexia.

Methods:

The study was conducted with one-group pretest–posttest. Participants received 2 mA transcranial direct current stimulation during 30 minutes for 5 consecutive days. Reading performance was measured by a group of tasks (identification and reading of letters, syllables, words, nonwords, and text).

Results:

A significant increase in the number of correct answers for nonwords and text tasks was observed after transcranial direct current stimulation (P = .035 and P = .012, respectively).

Conclusion:

The transcranial direct current stimulation seems to be a promising tool for the treatment of reading problems in dyslexia. Future studies are necessary to confirm the effects of transcranial direct current stimulation and to establish optimal intervention protocol in this population.

Therapeutic Applications of Noninvasive Neuromodulation in Children and Adolescents

Recent advances and growing evidence supporting the safety and efficacy of noninvasive neuromodulatory techniques in adults have facilitated the study of neuromodulation applications in children and adolescents. Noninvasive brain stimulation methods such as transcranial direct current stimulation and transcranial magnetic stimulation have been considered in children with depression, autism spectrum disorder, attention-deficit hyperactivity disorder, and other neuropsychiatric disorders. However, current clinical applications of neuromodulation techniques in children and adolescents are nascent. There is a great need for developmentally informed, large, double-blinded, randomized, controlled clinical trials to demonstrate efficacy and safety of noninvasive brain stimulation in children and adolescents.

Non-Invasive Brain Stimulation in Children With Unilateral Cerebral Palsy: A Protocol and Risk Mitigation Guide

Non-invasive brain stimulation has been increasingly investigated, mainly in adults, with the aims of influencing motor recovery after stroke. However, a consensus on safety and optimal study design has not been established in pediatrics. The low incidence of reported major adverse events in adults with and without clinical conditions has expedited the exploration of NIBS in children with paralleled purposes to influence motor skill development after neurological injury. Considering developmental variability in children, with or without a neurologic diagnosis, adult dosing and protocols may not be appropriate. The purpose of this paper is to present recommendations and tools for the prevention and mitigation of adverse events (AEs) during NIBS in children with unilateral cerebral palsy (UCP). Our recommendations provide a framework for pediatric NIBS study design. The key components of this report on NIBS AEs are (a) a summary of related literature to provide the background evidence and (b) tools for anticipating and managing AEs from four international pediatric laboratories. These recommendations provide a preliminary guide for the assessment of safety and risk mitigation of NIBS in children with UCP. Consistent reporting of safety, feasibility, and tolerability will refine NIBS practice guidelines contributing to future clinical translations of NIBS.

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines

Low intensity transcranial electrical stimulation (TES) in humans, encompassing transcranial direct current (tDCS), transcutaneous spinal Direct Current Stimulation (tsDCS), transcranial alternating current (tACS), and transcranial random noise (tRNS) stimulation or their combinations, appears to be safe. No serious adverse events (SAEs) have been reported so far in over 18,000 sessions administered to healthy subjects, neurological and psychiatric patients, as summarized here. Moderate adverse events (AEs), as defined by the necessity to intervene, are rare, and include skin burns with tDCS due to suboptimal electrode-skin contact. Very rarely mania or hypomania was induced in patients with depression (11 documented cases), yet a causal relationship is difficult to prove because of the low incidence rate and limited numbers of subjects in controlled trials. Mild AEs (MAEs) include headache and fatigue following stimulation as well as prickling and burning sensations occurring during tDCS at peak-to-baseline intensities of 1-2mA and during tACS at higher peak-to-peak intensities above 2mA. The prevalence of published AEs is different in studies specifically assessing AEs vs. those not assessing them, being higher in the former. AEs are frequently reported by individuals receiving placebo stimulation. The profile of AEs in terms of frequency, magnitude and type is comparable in healthy and clinical populations, and this is also the case for more vulnerable populations, such as children, elderly persons, or pregnant women. Combined interventions (e.g., co-application of drugs, electrophysiological measurements, neuroimaging) were not associated with further safety issues. Safety is established for low-intensity 'conventional' TES defined as <4mA, up to 60min duration per day. Animal studies and modeling evidence indicate that brain injury could occur at predicted current densities in the brain of 6.3-13A/m2 that are over an order of magnitude above those produced by tDCS in humans. Using AC stimulation fewer AEs were reported compared to DC. In specific paradigms with amplitudes of up to 10mA, frequencies in the kHz range appear to be safe. In this paper we provide structured interviews and recommend their use in future controlled studies, in particular when trying to extend the parameters applied. We also discuss recent regulatory issues, reporting practices and ethical issues. These recommendations achieved consensus in a meeting, which took place in Göttingen, Germany, on September 6-7, 2016 and were refined thereafter by email correspondence.

Non-invasive brain stimulation for dystonia: therapeutic implications

Dystonia is characterized by excessive muscle contractions giving rise to abnormal posture and involuntary twisting movements. Although dystonia syndromes are a heterogeneous group of disorders, certain pathophysiological mechanisms have been consistently identified across different forms. These pathophysiological mechanisms have subsequently been exploited for the development of non-invasive brain stimulation (NIBS) techniques able to modulate neural activity in one or more nodes of the putative network that is altered in dystonia, and the therapeutic role of NIBS has hence been suggested. Here all studies that applied such techniques as a therapeutic intervention in any forms of dystonia, including the few works performed in children, are reviewed and emerging concepts and pitfalls of NIBS are discussed.

Applications of transcranial direct current stimulation in children and pediatrics

Transcranial direct current stimulation (tDCS) is a neuromodulatory noninvasive brain stimulation tool with potential to increase or reduce regional and remote cortical excitability. Numerous studies have shown the ability of this technique to induce neuroplasticity and to modulate cognition and behavior in adults. Clinical studies have also demonstrated the ability of tDCS to induce therapeutic effects in several central nervous system disorders. However, knowledge about its ability to modulate brain functions in children or induce clinical improvements in pediatrics is limited. The objective of this review is to describe relevant data of some recent studies that may help to understand the potential of this technique in children with specific regard to effective and safe treatment of different developmental disorders in pediatrics. Overall, the results show that standard protocols of tDCS are well tolerated by children and have promising clinical effects. Nevertheless, treatment effects seem to be partially heterogeneous, and a case of a seizure in a child with previous history of infantile spasms and diagnosed epilepsy treated with tDCS for spasticity was reported. Further research is needed to determine safety criteria for tDCS use in children and to elucidate the particular neurophysiological changes induced by this neuromodulatory technique when it is applied in the developing brain.

Scaled Vibratory Feedback Can Bias Muscle Use in Children With Dystonia During a Redundant, 1-Dimensional Myocontrol Task

Vibratory feedback can be a useful tool for rehabilitation. We examined its use in children with dystonia to understand how it affects muscle activity in a population that does not respond well to standard rehabilitation. We predicted scaled vibration (ie, vibration that was directly or inversely proportional to muscle activity) would increase use of the vibrated muscle because of task-relevant sensory information, whereas nonscaled vibration would not change muscle use. The study was conducted on 11 subjects with dystonia and 14 controls. Each subject underwent 4 different types of vibration on the more dystonic biceps muscle (or nondominant arm in controls) in a 1-dimensional, bimanual myocontrol task. Our results showed that only scaled vibratory feedback could bias muscle use without changing overall performance in children with dystonia. We believe there may be a role in rehabilitation for scaled vibratory feedback to retrain abnormal muscle patterns.

Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS)

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.

Corticospinal Excitability in Children with Congenital Hemiparesis

Transcranial magnetic stimulation (TMS) can be used as an assessment or intervention to evaluate or influence brain activity in children with hemiparetic cerebral palsy (CP) commonly caused by perinatal stroke. This communication report analyzed data from two clinical trials using TMS to assess corticospinal excitability in children and young adults with hemiparetic CP. The results of this communication revealed a higher probability of finding a motor evoked potential (MEP) on the non-lesioned hemisphere compared to the lesioned hemisphere (p = 0.005). The resting motor threshold (RMT) was lower on the non-lesioned hemisphere than the lesioned hemisphere (p = 0.013). There was a significantly negative correlation between age and RMT (r_s = −0.65, p = 0.003). This communication provides information regarding MEP responses, motor thresholds (MTs) and the association with age during TMS assessment in children with hemiparetic CP. Such findings contribute to the development of future pediatric studies in neuroplasticity and neuromodulation to influence motor function and recovery after perinatal stroke.

Safety of Transcranial Direct Current Stimulation: Evidence Based Update 2016

This review updates and consolidates evidence on the safety of transcranial Direct Current Stimulation (tDCS). Safety is here operationally defined by, and limited to, the absence of evidence for a Serious Adverse Effect, the criteria for which are rigorously defined. This review adopts an evidence-based approach, based on an aggregation of experience from human trials, taking care not to confuse speculation on potential hazards or lack of data to refute such speculation with evidence for risk. Safety data from animal tests for tissue damage are reviewed with systematic consideration of translation to humans. Arbitrary safety considerations are avoided. Computational models are used to relate dose to brain exposure in humans and animals. We review relevant dose-response curves and dose metrics (e.g. current, duration, current density, charge, charge density) for meaningful safety standards. Special consideration is given to theoretically vulnerable populations including children and the elderly, subjects with mood disorders, epilepsy, stroke, implants, and home users. Evidence from relevant animal models indicates that brain injury by Direct Current Stimulation (DCS) occurs at predicted brain current densities (6.3-13 A/m(2)) that are over an order of magnitude above those produced by conventional tDCS. To date, the use of conventional tDCS protocols in human trials (≤40 min, ≤4 milliamperes, ≤7.2 Coulombs) has not produced any reports of a Serious Adverse Effect or irreversible injury across over 33,200 sessions and 1000 subjects with repeated sessions. This includes a wide variety of subjects, including persons from potentially vulnerable populations.

Transcranial direct current stimulation in children and adolescents: a comprehensive review

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method that has shown promising results in various neuropsychiatric disorders in adults. This review addresses the therapeutic use of tDCS in children and adolescents including safety, ethical, and legal considerations. There are several studies addressing the dosage of tDCS in children and adolescents by computational modeling of electric fields in the pediatric brain. Results suggest halving the amperage used in adults to obtain the same peak electric fields, however, there are some studies reporting on the safe application of tDCS with standard adult parameters in children (2 mA; 20-30 min). There are several randomized placebo controlled trials suggesting beneficial effects of tDCS for the treatment of cerebral palsy. For dystonia there are mixed data. Some studies suggest efficacy of tDCS for the treatment of refractory epilepsy, and for the improvement of attention deficit/hyperactivity disorder and autism. Interestingly, there is a lack of data for the treatment of childhood and adolescent psychiatric disorders, i.e., childhood onset schizophrenia and affective disorders. Overall, tDCS seems to be safe in pediatric population. More studies are needed to confirm the preliminary encouraging results; however, ethical deliberation has to be weighed carefully for every single case.

Current and emerging strategies for treatment of childhood dystonia

Childhood dystonia is a movement disorder characterized by involuntary sustained or intermittent muscle contractions causing twisting and repetitive movements, abnormal postures, or both (Sanger et al, 2003). Dystonia is a devastating neurological condition that prevents the acquisition of normal motor skills during critical periods of development in children. Moreover, it is particularly debilitating in children when dystonia affects the upper extremities such that learning and consolidation of common daily motor actions are impeded. Thus, the treatment and rehabilitation of dystonia is a challenge that continuously requires exploration of novel interventions. This review will initially describe the underlying neurophysiological mechanisms of the motor impairments found in childhood dystonia followed by the clinical measurement tools that are available to document the presence and severity of symptoms. Finally, we will discuss the state-of-the-art of therapeutic options for childhood dystonia, with particular emphasis on emergent and innovative strategies.