Single-pulse transcranial magnetic stimulation for assessment of motor development in infants with early brain injury

INTRODUCTION

Single-pulse transcranial magnetic stimulation (TMS) has many applications for pediatric clinical populations, including infants with perinatal brain injury. As a noninvasive neuromodulation tool, single-pulse TMS has been used safely in infants and children to assess corticospinal integrity and circuitry patterns. TMS may have important applications in early detection of atypical motor development or cerebral palsy.

AREAS COVERED

The authors identified and summarized relevant studies incorporating TMS in infants, including findings related to corticospinal development and circuitry, motor cortex localization and mapping, and safety. This special report also describes methodologies and safety considerations related to TMS assessment in infants, and discusses potential applications related to diagnosis of cerebral palsy and early intervention.

EXPERT OPINION

Single-pulse TMS has demonstrated safety and feasibility in infants with perinatal brain injury and may provide insight into neuromotor development and potential cerebral palsy diagnosis. Additional research in larger sample sizes will more fully evaluate the utility of TMS biomarkers in early diagnosis and intervention. Methodological challenges to performing TMS in infants and technical/equipment limitations require additional consideration and innovation toward clinical implementation. Future research may explore use of noninvasive neuromodulation techniques as an intervention in younger children with perinatal brain injury to improve motor outcomes.

Anodal Contralesional tDCS Enhances CST Excitability Bilaterally in an Adolescent with Hemiparetic Cerebral Palsy: A Brief Report

Hemiparetic cerebral palsy (HCP), weakness on one side of the body typically caused by perinatal stroke, is characterized by lifelong motor impairments related to alterations in the corticospinal tract (CST). CST reorganization could be a useful biomarker to guide applications of neuromodulatory interventions, such as transcranial direct current stimulation (tDCS), to improve the effectiveness of rehabilitation therapies. We evaluated an adolescent with HCP and CST reorganization who demonstrated persistent heightened CST excitability in both upper limbs following anodal contralesional tDCS. The results support further investigation of targeted tDCS as an adjuvant therapy to traditional neurorehabilitation for upper limb function.

Safety and feasibility of transcranial direct current stimulation stratified by corticospinal organization in children with hemiparesis

Children with hemiparesis (CWH) due to stroke early in life face lifelong impairments in motor function. Transcranial direct current stimulation (tDCS) may be a safe and feasible adjuvant therapy to augment rehabilitation. Given the variability in outcomes following tDCS, tailored protocols of tDCS are required. We evaluated the safety, feasibility, and preliminary effects of a single session of targeted anodal tDCS based on individual corticospinal tract organization on corticospinal excitability. Fourteen CWH (age = 13.8 ± 3.63) were stratified into two corticospinal organization subgroups based on transcranial magnetic stimulation (TMS)-confirmed motor evoked potentials (MEP): ipsilesional MEP presence (MEPIL+) or absence (MEPIL-). Subgroups were randomized to real anodal or sham tDCS (1.5 mA, 20 min) applied to the ipsilesional (MEPIL + group) or contralesional (MEPIL- group) hemisphere combined with hand training. Safety was assessed with questionnaires and motor function evaluation, and corticospinal excitability was assessed at baseline and every 15 min for 1 h after tDCS. No serious adverse events occurred and anticipated minor side effects were reported and were self-limiting. Six of 14 participants had consistent ipsilesional MEPs (MEPIL + group). Paretic hand MEP amplitude increased in 5/8 participants who received real anodal tDCS to either the ipsilesional or contralesional hemisphere (+80% change). Application of tDCS based on individual corticospinal organization was safe and feasible with expected effects on excitability, indicating the potential for tailored tDCS protocols for CWH. Additional research involving expanded experimental designs is needed to confirm these effects and to determine if this approach can be translated into a clinically relevant intervention.

Can Technology Improve Participation From Underserved Children and Families in Rehabilitation Research?

The COVID-19 pandemic led to the suspension of research studies, exposing many of the limitations of in-person research conducted within a laboratory or clinical setting. However, these limitations existed long before the pandemic and have contributed to small and unrepresentative samples. The pandemic has provided an opportunity to re-evaluate the focus of pediatric rehabilitation research, utilizing existing technology for remote and offsite research that does not require in-person visits. The goals of this shift are to enhance engagement and participation in research and to better meet the needs of participants and their families. We describe how this shift could be applied to assessing children’s motor development outside the laboratory with everyday technology as a model for future research and clinical study. Adapting research protocols will serve a larger and more representative population of children and address inequities in research participation.

Remotely monitored transcranial direct current stimulation in pediatric cerebral palsy: open label trial protocol

BACKGROUND

Pediatric applications of non-invasive brain stimulation using transcranial direct current stimulation (tDCS) have demonstrated its safety with few adverse events reported. Remotely monitored tDCS, as an adjuvant intervention to rehabilitation, may improve quality of life for children with cerebral palsy (CP) through motor function improvements, reduced treatment costs, and increased access to tDCS therapies. Our group previously evaluated the feasibility of a remotely monitored mock tDCS setup in which families and children successfully demonstrated the ability to follow tDCS instructional guidance.

METHODS AND DESIGN

Here, we designed a protocol to investigate the feasibility, safety, and tolerability of at-home active transcranial direct current stimulation in children with CP with synchronous supervision from laboratory investigators. Ten participants will be recruited to participate in the study for 5 consecutive days with the following sessions: tDCS setup practice on day 1, sham tDCS on day 2, and active tDCS on days 3-5. Sham stimulation will consist of an initial 30-second ramp up to 1.5 mA stimulation followed by a 30-second ramp down. Active stimulation will be delivered at 1.0 - 1.5 mA for 20 minutes and adjusted based on child tolerance. Feasibility will be evaluated via photographs of montage setup and the quality of stimulation delivery. Safety and tolerability will be assessed through an adverse events survey, the Box and Blocks Test (BBT) motor assessment, and a setup ease/comfort survey.

DISCUSSION

We expect synchronous supervision of at-home teleneuromodulation to be tolerable and safe with increasing stimulation quality over repeated sessions when following a tDCS setup previously determined to be feasible. The findings will provide opportunity for larger clinical trials exploring efficacy and illuminate the potential of remotely monitored tDCS in combination with rehabilitation interventions as a means of pediatric neurorehabilitation. This will demonstrate the value of greater accessibility of non-invasive brain stimulation interventions and ultimately offer the potential to improve care and quality of life for children and families with CP.

TRIAL REGISTRATION

October 8, 2021( https://clinicaltrials.gov/ct2/show/NCT05071586 ).

Disrupted Access to Therapies and Impact on Well-Being During the COVID-19 Pandemic for Children With Motor Impairment and Their Caregivers

OBJECTIVES

The aim of this study was to determine the impact of the COVID-19 pandemic on access to rehabilitation therapies and the impact of changes in therapy access on the physical and mental well-being of children with motor impairment and their caregivers.

DESIGN

Caregivers of children younger than 18 yrs with childhood-onset motor impairment (primarily cerebral palsy) completed an anonymous survey through the online platform REDCap between May 5 and July 13, 2020.

RESULTS

The survey was completed by 102 participants. Before the pandemic, 92 of 102 children (90%) were receiving one or more therapies; at the time surveyed, 55 children (54%) were receiving any therapies (P < 0.001). More than 40% of the sample reported increased child stress, decreased physical activity, and/or decline in mobility/movement. Participants who reported a decrease in number of therapies at the time surveyed more frequently reported lower satisfaction with treatment delivery (P < 0.001), a decline in child's mobility (P = 0.001), and increased caregiver stress (P = 0.004). Five qualitative themes were identified from open-ended question responses related to therapies and well-being.

CONCLUSIONS

Access to pediatric rehabilitation therapies was disrupted during COVID-19. Disrupted access may be related to impact on physical and mental health. With the expansion of telehealth, caregiver and child feedback should be incorporated to optimize benefit.

From adults to pediatrics: A review noninvasive brain stimulation (NIBS) to facilitate recovery from brain injury

Stroke is a major problem worldwide that impacts over 100 million adults and children annually. Rehabilitation therapy is the current standard of care to restore functional impairments post-stroke, however its effects are limited and many patients suffer persisting functional impairments and life-long disability. Noninvasive Brain Stimulation (NIBS) has emerged as a potential rehabilitation treatment option in both adults and children with brain injury. In the last decade, Transcranial Magnetic Stimulation (TMS), Transcranial Direct Current Stimulation (tDCS) and Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) have been investigated to improve motor recovery in adults post-stroke. These promising adult findings using NIBS, however, have yet to be widely translated to the area of pediatrics. The limited studies exploring NIBS in children have demonstrated safety, feasibility, and utility of stimulation-augmented rehabilitation. This chapter will describe the mechanism of NIBS therapy (cortical excitability, neuroplasticity) that underlies its use in stroke and motor function and how TMS, tDCS, and taVNS are applied in adult stroke treatment paradigms. We will then discuss the current state of NIBS in early pediatric brain injury and will provide insight regarding practical considerations and future applications of NIBS in pediatrics to make this promising treatment option a viable therapy in children.

Evaluating transcranial magnetic stimulation (TMS) induced electric fields in pediatric stroke

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Numerical TMS simulations were performed over and around perinatal stroke lesions.

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The presence of brain lesions locally affects the electric field distribution.

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Brain lesions do not significantly change the mean electric field strength.

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Model driven approaches can inform TMS dosing in a pediatric stroke population.

Transcranial magnetic stimulation (TMS) is an increasingly popular tool for stroke rehabilitation. Consequently, researchers have started to explore the use of TMS in pediatric stroke. However, the application of TMS in a developing brain with pathologies comes with a unique set of challenges. The effect of TMS-induced electric fields has not been explored in children with stroke lesions. Here, we used finite element method (FEM) modeling to study how the electric field strength is affected by the presence of a lesion. We created individual realistic head models from MRIs (n = 6) of children with unilateral cerebral palsy due to perinatal stroke. We conducted TMS electric field simulations for coil locations over lesioned and non-lesioned hemispheres. We found that the presence of a lesion can strongly affect the electric field distribution. On the group level, the mean electric field strength did not differ between lesioned and non-lesioned hemispheres but exhibited a greater variability in the lesioned hemisphere. Other factors such as coil-to-cortex distance have a strong influence on the TMS electric field even in the presence of lesions. Our study has important implications for the delivery of TMS in children with brain lesions with respect to TMS dosing and coil placement.

Cardiovascular Effects of Transcranial Direct Current Stimulation and Bimanual Training in Children With Cerebral Palsy

PURPOSE

To determine the influence of combined transcranial direct current stimulation (tDCS) to the motor cortex (M1) and bimanual training on cardiovascular function in children with cerebral palsy (CP).

METHODS

Mean arterial pressure (MAP), heart rate (HR), and HR variability (HRV) were measured immediately before and after 20 minutes of cathodal tDCS to contralesional M1 and bimanual training on days 1, 6, and 10 of a 10-day trial in 8 participants (5 females, 7-19 years).

RESULTS

Baseline MAP and HR were similar across days (93 ± 10 mm Hg and 90 ± 10 bpm, P > .05). MAP was similar from baseline to postintervention across all 3 days. Systolic pressure, diastolic pressure, nor HR significantly changed. HRV was not influenced by the 10-day intervention.

CONCLUSIONS

Combined cathodal tDCS to M1 and bimanual training does not influence autonomic and cardiovascular function in children with CP due to perinatal stroke.

Guidelines for TMS/tES clinical services and research through the COVID-19 pandemic

BACKGROUND

The COVID-19 pandemic has broadly disrupted biomedical treatment and research including non-invasive brain stimulation (NIBS). Moreover, the rapid onset of societal disruption and evolving regulatory restrictions may not have allowed for systematic planning of how clinical and research work may continue throughout the pandemic or be restarted as restrictions are abated. The urgency to provide and develop NIBS as an intervention for diverse neurological and mental health indications, and as a catalyst of fundamental brain research, is not dampened by the parallel efforts to address the most life-threatening aspects of COVID-19; rather in many cases the need for NIBS is heightened including the potential to mitigate mental health consequences related to COVID-19.

OBJECTIVE

To facilitate the re-establishment of access to NIBS clinical services and research operations during the current COVID-19 pandemic and possible future outbreaks, we develop and discuss a framework for balancing the importance of NIBS operations with safety considerations, while addressing the needs of all stakeholders. We focus on Transcranial Magnetic Stimulation (TMS) and low intensity transcranial Electrical Stimulation (tES) - including transcranial Direct Current Stimulation (tDCS) and transcranial Alternating Current Stimulation (tACS).

METHODS

The present consensus paper provides guidelines and good practices for managing and reopening NIBS clinics and laboratories through the immediate and ongoing stages of COVID-19. The document reflects the analysis of experts with domain-relevant expertise spanning NIBS technology, clinical services, and basic and clinical research - with an international perspective. We outline regulatory aspects, human resources, NIBS optimization, as well as accommodations for specific demographics.

RESULTS

A model based on three phases (early COVID-19 impact, current practices, and future preparation) with an 11-step checklist (spanning removing or streamlining in-person protocols, incorporating telemedicine, and addressing COVID-19-associated adverse events) is proposed. Recommendations on implementing social distancing and sterilization of NIBS related equipment, specific considerations of COVID-19 positive populations including mental health comorbidities, as well as considerations regarding regulatory and human resource in the era of COVID-19 are outlined. We discuss COVID-19 considerations specifically for clinical (sub-)populations including pediatric, stroke, addiction, and the elderly. Numerous case-examples across the world are described.

CONCLUSION

There is an evident, and in cases urgent, need to maintain NIBS operations through the COVID-19 pandemic, including anticipating future pandemic waves and addressing effects of COVID-19 on brain and mind. The proposed robust and structured strategy aims to address the current and anticipated future challenges while maintaining scientific rigor and managing risk.

Ipsilateral Corticospinal Tract Excitability Contributes to the Severity of Mirror Movements in Unilateral Cerebral Palsy: A Case Series

Mirror movements (MM) can be a clinical manifestation of unilateral cerebral palsy (UCP) causing involuntary movements when attempting to use either hand for functional activities. Atypical development of the corticospinal tract (CST) contributes to impairments in observed motor movements and functional activities. However, little is known about the underlying neurophysiology and contribution of the CST to MM. The current case study characterizes MM in 13 children and young adults with UCP ranging in age from 7 to 19 years and includes clinical and neurophysiologic variables. Clinical profiles included MM of each hand (ie, Woods and Teuber), bimanual coordination and hand use (Assisting Hand Assessment [AHA]), and perception of performance (Canadian Occupational Performance Measure [COPM]). We measured the strength of motor-evoked potentials (MEP) elicited from single-pulse transcranial magnetic stimulation (TMS) of each hemisphere to create a ratio of hemispheric responses. Our sample included three types of CST circuitry: ipsilateral (n = 5), bilateral (n = 3), and contralateral (n = 4). The MEP ratio ranged from 0 to 1.45 (median 0.11) with greater MM observed in participants with ratios greater than 0.5. We observed a positive relationship between the MEP ratio and the more-affected MM score, meaning participants with larger ipsilateral responses from contralesional stimulation (eg, the contralesional hemisphere was stimulated with TMS resulting in an ipsilateral MEP response), as compared with contralateral responses, displayed greater MM than those that did not. There was no relationship between MM and function as measured by the AHA or COPM. These findings suggest a role of the contralesional hemisphere to MM, which could serve as a therapeutic target for interventions.

A retrospective qualitative report of symptoms and safety from transcranial focused ultrasound for neuromodulation in humans

Low intensity transcranial focused ultrasound (LIFU) is a promising method of non-invasive neuromodulation that uses mechanical energy to affect neuronal excitability. LIFU confers high spatial resolution and adjustable focal lengths for precise neuromodulation of discrete regions in the human brain. Before the full potential of low intensity ultrasound for research and clinical application can be investigated, data on the safety of this technique is indicated. Here, we provide an evaluation of the safety of LIFU for human neuromodulation through participant report and neurological assessment with a comparison of symptomology to other forms of non-invasive brain stimulation. Participants (N = 120) that were enrolled in one of seven human ultrasound neuromodulation studies in one laboratory at the University of Minnesota (2015–2017) were queried to complete a follow-up Participant Report of Symptoms questionnaire assessing their self-reported experience and tolerance to participation in LIFU research (I_sppa 11.56–17.12 W/cm²) and the perceived relation of symptoms to LIFU. A total of 64/120 participant (53%) responded to follow-up requests to complete the Participant Report of Symptoms questionnaire. None of the participants experienced serious adverse effects. From the post-hoc assessment of safety using the questionnaire, 7/64 reported mild to moderate symptoms, that were perceived as ‘possibly’ or ‘probably’ related to participation in LIFU experiments. These reports included neck pain, problems with attention, muscle twitches and anxiety. The most common unrelated symptoms included sleepiness and neck pain. There were initial transient reports of mild neck pain, scalp tingling and headache that were extinguished upon follow-up. No new symptoms were reported upon follow up out to 1 month. The profile and incidence of symptoms looks to be similar to other forms of non-invasive brain stimulation.

Influence of Repetitive Transcranial Magnetic Stimulation on Human Neurochemistry and Functional Connectivity: A Pilot MRI/MRS Study at 7 T

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation method commonly used in the disciplines of neuroscience, neurology, and neuropsychiatry to examine or modulate brain function. Low frequency rTMS (e.g., 1 Hz) is associated with a net suppression of cortical excitability, whereas higher frequencies (e.g., 5 Hz) purportedly increase excitability. Magnetic resonance spectroscopy (MRS) and resting-state functional MRI (rsfMRI) allow investigation of neurochemistry and functional connectivity, respectively, and can assess the influence of rTMS in these domains. This pilot study investigated the effects of rTMS on the primary motor cortex using pre and post MRS and rsfMRI assessments at 7 T. Seven right-handed males (age 27 ± 7 y.o.) underwent single-voxel MRS and rsfMRI before and about 30-min after rTMS was administered outside the scanner for 20-min over the primary motor cortex of the left (dominant) hemisphere. All participants received 1-Hz rTMS; one participant additionally received 5-Hz rTMS in a separate session. Concentrations of 17 neurochemicals were quantified in left and right motor cortices. Connectivity metrics included fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo) of both motor cortices, strength of related brain networks, and inter-hemispheric connectivity. The group-analysis revealed few trends (i.e., uncorrected for multiple comparisons), including a mean increase in the concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) after the inhibitory rTMS protocol as compared to baseline in the stimulated (left) motor cortex (+8%, p = 0.043), along with a slight increase of total creatine (+2%, p = 0.018), and decrease of aspartate (-18%, p = 0.016). Additionally, GABA tended to decrease in the contralateral hemisphere (-6%, p = 0.033). No other changes of metabolite concentrations were found. Whereas functional connectivity outcomes did not exhibit trends of significant changes induced by rTMS, the percent changes of few connectivity metrics in both hemispheres were negatively correlated with GABA changes in the contralateral hemisphere. While studies in larger cohorts are needed to confirm these preliminary findings, our results indicate the safety and feasibility of detecting changes in key metabolites associated with neurotransmission after a single 1-Hz rTMS session, establishing the construct for future exploration of the neurochemical, and connectivity mechanisms of cortical responses to neuromodulation.

Bimanual Skill Learning after Transcranial Direct Current Stimulation in Children with Unilateral Cerebral Palsy: A Brief Report

Bimanual skills are important for goal-oriented activities. Children with unilateral cerebral palsy (UCP) have deficits in unimanual and bimanual motor control and learning. The application of non-invasive brain stimulation with existing motor training may further promote motor learning; however, the effects of stimulation on bimanual learning have not been examined. Here, we assessed the performance of a novel bimanual skill (modified Speed Stacks task) in eight children with UCP before, during, and after a combined motor training and brain stimulation intervention. Participants received 10 days (120 min/day) of goal-oriented bimanual therapy combined initially with transcranial direct current stimulation (tDCS, 20 min/day). Results showed task improvement tapered (p < 0.001) during and after the intervention and task variability decreased in 6/8 participants, indicating the potential impact of novel rehabilitation to improve skill learning in children with UCP. Future work is required to understand how both tDCS and bimanual training contribute to learning bimanual tasks.

Motor Evoked Potentials as Potential Biomarkers of Early Atypical Corticospinal Tract Development in Infants with Perinatal Stroke

Diagnosis of cerebral palsy (CP) after perinatal stroke is often delayed beyond infancy, a period of rapid neuromotor development with heightened potential for rehabilitation. This study sought to assess whether the presence or absence of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) could be an early biomarker of atypical development within the first year of life. In 10 infants with perinatal stroke, motor outcome was assessed with a standardized movement assessment. Single-pulse TMS was utilized to assess presence of MEPs. Younger infants (3-6 months CA, n = 5, 4/5 (80%)) were more likely to present with an MEP from the more-affected hemisphere (MAH) compared to older infants (7-12 months CA, n = 5, 0/5, (0%)) (p = 0.048). Atypical movement was demonstrated in the majority of infants with an absent MEP from the MAH (5/6, 83%) compared to those with a present MEP (1/4, 25%) (p = 0.191). We found that age influences the ability to elicit an MEP from the MAH, and motor outcome may be related to MAH MEP absence. Assessment of MEPs in conjunction with current practice of neuroimaging and motor assessments could promote early detection and intervention in infants at risk of CP.

Neurite orientation dispersion and density imaging quantifies corticospinal tract microstructural organization in children with unilateral cerebral palsy

Children with unilateral cerebral palsy (UCP) due to early brain injury exhibit disrupted connectivity of corticospinal tracts (CSTs), which can be quantified using diffusion-weighted magnetic resonance imaging (DWI). Diffusion tensor imaging (DTI) is commonly used to quantify white matter organization, however, this model lacks the biological specificity to accurately describe underlying microstructural properties. Newer approaches, such as neurite orientation dispersion and density imaging (NODDI), may provide more biologically accurate information regarding CST microstructure. In this study, we directly compared metrics of CST microstructure using NODDI and DTI models to characterize the microstructural organization of corticospinal pathways. Twenty participants with UCP participating in a neuromodulation/rehabilitation intervention underwent imaging including multi-shell DWI; 10 participants' datasets were adequately completed for neuroimaging analysis. Task fMRI-guided probabilistic tractography from motor cortex to brainstem was performed at baseline and follow-up to reconstruct the CSTs. Diffusion metrics were compared between hemispheres at baseline, and between baseline and follow-up to test for intervention effects. Correlation analyses were used to compare baseline metrics to changes in hand function following the intervention. DTI results showed that mean fractional anisotropy in lesioned and nonlesioned CSTs did not significantly differ, but mean, axial, and radial diffusivity were greater in the lesioned CST. For NODDI, intracellular volume fraction (ICVF) and orientation dispersion index (ODI) were lower in the lesioned CST. Unimanual function was strongly correlated with ICVF, but not FA. NODDI may reveal distinct properties of CST microstructure that are linked to motor function, indicating their potential in characterizing brain structure and development.

Influence of Combined Transcranial Direct Current Stimulation and Motor Training on Corticospinal Excitability in Children With Unilateral Cerebral Palsy

Combined non-invasive brain stimulation (NIBS) and rehabilitation interventions have the potential to improve function in children with unilateral cerebral palsy (UCP), however their effects on developing brain function are not well understood. In a proof-of-principle study, we used single-pulse transcranial magnetic stimulation (TMS) to measure changes in corticospinal excitability and relationships to motor performance following a randomized controlled trial consisting of 10 days of combined constraint-induced movement therapy (CIMT) and cathodal transcranial direct current stimulation (tDCS) applied to the contralesional motor cortex. Twenty children and young adults (mean age = 12 years, 9 months, range = 7 years, 7 months, 21 years, 7 months) with UCP participated. TMS testing was performed before, after, and 6 months after the intervention to measure motor evoked potential (MEP) amplitude and cortical silent period (CSP) duration. The association between neurophysiologic and motor outcomes and differences in excitability between hemispheres were examined. Contralesional MEP amplitude decreased as hypothesized in five of five participants receiving active tDCS immediately after and 6 months after the intervention, however no statistically significant differences between intervention groups were noted for MEP amplitude [mean difference = −323.9 μV, 95% CI = (−989, 341), p = 0.34] or CSP duration [mean difference = 3.9 ms, 95% CI = (−7.7, 15.5), p = 0.51]. Changes in corticospinal excitability were not statistically associated with improvements in hand function after the intervention. Across all participants, MEP amplitudes measured in the more-affected hand from both contralesional (mean difference = −474.5 μV) and ipsilesional hemispheres (−624.5 μV) were smaller compared to the less-affected hand. Assessing neurophysiologic changes after tDCS in children with UCP provides an understanding of long-term effects on brain excitability to help determine its potential as a therapeutic intervention. Additional investigation into the neurophysiologic effects of tDCS in larger samples of children with UCP are needed to confirm these findings.

Electrode Placement in Transcranial Direct Current Stimulation-How Reliable Is the Determination of C3/C4?

The 10/20 electroencephalogram (EEG) measurements system often guides electrode placement for transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation. One targeted region of the brain is the primary motor cortex (M1) for motor recovery after stroke, among other clinical indications. M1 is identified by C3 and C4 of the 10/20 EEG system yet the reliability of 10/20 EEG measurements by novice research raters is unknown. We investigated the reliability of the 10/20 EEG measurements for C3 and C4 in 25 adult participants. Two novice raters were assessed for inter-rater reliability. Both raters received two hours of instruction from a registered neurodiagnostic technician. One of the raters completed the measurements across two testing days for intra-rater reliability. Relative reliability was determined using the intraclass coefficient (ICC) and absolute reliability. We observed a low to fair inter and intra-rater ICC for motor cortex measurements. The absolute reliability was <1.0 cm by different novice raters and on different days. Although a low error was observed, consideration of the integrity of the targeted region of the brain is critical when designing tDCS interventions in clinical populations who may have compromised brain structure, due to a lesion or altered anatomy.

Reference values of intrinsic muscle strength of the hand of adolescents and young adults

STUDY DESIGN

A cross-sectional clinical measurement study.

INTRODUCTION

Measuring intrinsic hand muscle strength helps evaluate hand function or therapeutic outcomes. However, there are no established normative values in adolescents and young adults between 13 and 20 years of age.

PURPOSE OF THE STUDY

To measure hand intrinsic muscle strength and identify associated factors that may influence such in adolescents and young adults through use of the Rotterdam intrinsic hand myometer.

METHODS

A total of 131 participants (male: 63; female: 68) between 13 and 20 years of age completed the strength measurements of abductor pollicis brevis, first dorsal interosseus (FDI), deep head of FDI and lumbrical of second digit, flexor pollicis brevis (FPB), and abductor digiti minimi. Two trials of the measurements of each muscle were averaged for analyses. Self-reported demographic data were used to examine the influences of age, sex, and body mass index (BMI) on intrinsic hand muscle strength.

RESULTS

Normative values of intrinsic hand muscle strength were presented by age groups (13, 14, 15-16, 17-18, 19-20 year olds) for each sex category (male, female). A main effect of sex, but not age, on all the muscles on both the dominant (FPB: P = .02, others: P < .001) and non-dominant (FDI: P = .005, FPB: P = .01, others: P < .001) sides was found. A significant effect of BMI was found on dominant (P = .009) and non-dominant abductor pollicis brevis (P = .002). In addition, FDI (P = .005) and FPB (P = .002) were stronger on the dominant side than the non-dominant side.

DISCUSSION

Intrinsic hand muscle strength may be influenced by different factors including sex, BMI, and hand dominance. A larger sample is needed to rigorously investigate the influence of age on intrinsic strength in male and female adolescents and young adults.

CONCLUSION

The results provide reference values and suggest factors to be considered when evaluating hand function and therapeutic outcomes in both clinical and research settings. Further study is recommended.

LEVEL OF EVIDENCE

VI.

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.

Less-Affected Hand Function in Children With Hemiparetic Unilateral Cerebral Palsy: A Comparison Study With Typically Developing Peers

BACKGROUND

Neurorehabilitation interventions in children with unilateral cerebral palsy (UCP) target motor abilities in daily life yet deficits in hand skills persist. Limitations in the less-affected hand may affect overall bimanual hand skills.

OBJECTIVE

To compare hand function, by timed motor performance on the Jebsen-Taylor Test of Hand Function (JTTHF) and grip strength of children with UCP to children with typical development (CTD), aged 8 to 18 years old. Exploratory analyses compared hand function measures with regard to neurophysiological outcomes measured by transcranial magnetic stimulation and between group comparisons of hemispheric motor threshold.

METHODS

Baseline hand skills were evaluated in 47 children (21 UCP; 26 CTD). Single-pulse transcranial magnetic stimulation testing assessed corticospinal tract and motor threshold.

RESULTS

The mean difference of the less-affected hand of children with UCP to the dominant hand of CTD on the JTTHF was 21.4 seconds (95% CI = 9.32-33.46, P = .001). The mean difference in grip strength was -30.8 N (95% CI = -61.9 to 0.31, P = .052). Resting motor thresholds between groups were not significant, but age was significantly associated with resting motor threshold ( P < .001; P = .001). Children with UCP ipsilateral pattern of motor representation demonstrated greater mean differences between hands than children with contralateral pattern of motor representation ( P < .001). All results were adjusted for age and sex.

CONCLUSIONS

The less-affected hand in children with UCP underperformed the dominant hand of CTD. Limitations were greater in children with UCP ipsilateral motor pattern. Rehabilitation in the less-affected hand may be warranted. Bilateral hand function in future studies may help identify the optimal rehabilitation and neuromodulatory intervention.

Determining Electrode Placement for Transcranial Direct Current Stimulation: A Comparison of EEG- Versus TMS-Guided Methods

Transcranial direct current stimulation (tDCS) is increasingly researched as an adjuvant to motor rehabilitation for children with hemiparesis. The optimal method for the primary motor cortex (M1) somatotopic localization for tDCS electrode placement has not been established. The objective, therefore, was to determine the location of the M1 derived using the 10/20 electroencephalography (EEG) system and transcranial magnetic stimulation (TMS) in children with hemiparesis (CWH) and a comparison group of typically developing children (TDC). We hypothesized a difference in location for CWH but not for TDC. The 2 locations were evaluated in 47 children (21 CWH, 26 TDC). Distances between the locations were measured pending presence of a motor evoked potential. Distances between the EEG and TMS locations that exceeded the 2.5 cm × 2.5 cm rubber electrode area are reported in percentages [95% confidence interval] in CWH-nonlesioned hemisphere was 68.8% [41.3-89.0], lesioned: 85.7% [57.2-98.2]; TDC-dominant hemisphere 73.9% [51.6-89.8], nondominant: 82.6% [61.2-95.0]. Distances that exceeded the 3 × 5 cm electrode sponge area in CWH-nonlesioned was 25.0% [7.3-52.4], lesioned was 28.6% [8.4-58.1]; TDC-dominant was 52.2% [30.6-73.2], nondominant was 43.5 [23.2-65.5]). Distances that exceeded the 5 × 7 cm electrode sponge area in CWH-nonlesioned was 18.8% [4.0-45.6] and lesioned was 21.4% [4.7-50.8]; TDC-dominant was 21.7% [7.5-43.7] and nondominant was 26.1% [10.2-48.4]. Individual variability in brain somatotopic organization may influence surface scalp localization of underlying M1 in children regardless of neurologic impairment. Findings suggest further investigation of optimal tDCS electrode placement. EEG and TMS methods reveal variability in localizing M1 in children regardless of stroke diagnosis. This study was registered on clinicaltrials.gov NCT02015338.

Stability of stereognosis after pediatric repetitive transcranial magnetic stimulation and constraint-induced movement therapy clinical trial

OBJECTIVE

Poor sensibility affecting stereognosis, the ability to discriminate objects without visual input, can potentiate disuse of the paretic limb following stroke. The purpose of this study was to examine potential change in stereognosis after intervention.

METHODS

Stereognosis testing in a secondary subgroup of 10 children with hemiparesis and baseline stereognosis deficits (ages 11-16) after a 13-day clinical trial of real or sham repetitive transcranial magnetic stimulation (rTMS) and constraint-induced movement therapy (CIMT) is reported. All children received 10 h of CIMT while wearing a cast full-time.

RESULTS

Post-trial, 80% of participants from both intervention groups demonstrated improvement in stereognosis (95% CI: 44.4%-97.5%). Pre-trial to long-term follow-up (range: 21-57 months), 60% retained gains or improved (95% CI: 26.2%-87.8%). Between-group differences were not detected.

DISCUSSION

Children demonstrated stereognosis change following intervention. Research on this change and potential minimal clinically important differences are indicated.

Repetitive Transcranial Magnetic Stimulation/Behavioral Intervention Clinical Trial: Long-Term Follow-Up of Outcomes in Congenital Hemiparesis

OBJECTIVE

The purpose of this study was to examine long-term outcomes of nonpharmacological intervention in children and adolescents with stroke utilizing repetitive transcranial magnetic stimulation (rTMS) to the primary motor cortex combined with constraint- induced movement therapy (CIMT) to improve motor function in the paretic hand. Outcome measures included function, satisfaction, and medical status review.

METHODS

Fourteen of the original 19 participants (74%) from our rTMS/CIMT clinical trial (real rTMS+CIMT, n = 8; and sham rTMS+CIMT, n = 6) were evaluated. The median age of the subjects at follow up was 13.4 years (range 11-20 years old, 50% male). Median time to follow-up was 47.5 months (range 21-57 months). Descriptive statistics were conducted using frequencies and counts. Motor performance was measured using the Assisting Hand Assessment (AHA) and Canadian Occupational Performance Measure (COPM). Satisfaction was reported with use of the COPM and TMS Tolerance Survey. Open-ended interview was conducted for feedback on study experience and subjective perspectives of current functional status.

RESULTS

Overall, seven of eight individuals who received real rTMS and five of six individuals who received sham rTMS maintained or improved AHA scores. Six of 14 participants reported new onset of co-occurring conditions (four individuals in the real rTMS group, two individuals in the sham rTMS group). The majority (86%) of participants reported study satisfaction. Review of medical status revealed co-occurring conditions including: Epilepsy, obsessive-compulsive disorder, anxiety, depression, unspecified mood disorder, and undiagnosed inattentiveness.

CONCLUSIONS

Long-term outcomes of rTMS/CIMT in pediatric stroke were investigated. Variability in performance and unattributed symptoms were noted. Considering the prevalence of co-occurring conditions in children and adolescents with stroke, new-onset symptoms were not attributed to original intervention. With the small sample size, the impact of rTMS on long-term outcomes cannot be fully determined from these data. Characterizing long-term outcomes through performance, participant perspectives, and medical status allows comprehensive assessment of rTMS/CIMT intervention efficacy.

Case report of vasovagal syncope associated with single pulse transcranial magnetic stimulation in a healthy adult participant

BACKGROUND

Non-invasive brain stimulation-related seizures or syncopal events are rare. However, we report on a syncopal event in a healthy female during a transcranial magnetic stimulation single-pulse testing session.

CASE PRESENTATION

A 47-year-old healthy female presented for a transcranial magnetic stimulation session involving single-pulse assessment of cortical excitability. During the session, the participant appeared to have a brief event involving fainting and myoclonic jerks of the upper extremities. Orthostatic assessment was performed after the event and physician evaluation determined that this was a vasovagal syncopal event. The ethical aspects of this neurophysiology testing protocol were reviewed by the University of Minnesota Institutional Review Board (IRB), and formal IRB approval was deemed unnecessary for single-pulse assessment of healthy control participants not directly involved in a research study. Informed consent was obtained by the participant, including review of potential adverse events.

CONCLUSION

Although rare and rarely reported, vasovagal syncopal events surrounding non-invasive brain stimulation do occur. Thorough pre-screening should incorporate assessment of history of syncope and a plan for risk mitigation if such an event should occur. A complete assessment of the impact of stimulation on the autonomic nervous system is unknown. As such studies expand into patients with myriad neurologic diagnoses, further studies on this effect, in both healthy control and patient populations, are warranted. Such knowledge could contribute to identification of the optimal study participant, and improvements in techniques of stimulation administration.

Ipsilesional motor-evoked potential absence in pediatric hemiparesis impacts tracking accuracy of the less affected hand

This study analyzed the relationship between electrophysiological responses to transcranial magnetic stimulation (TMS), finger tracking accuracy, and volume of neural substrate in children with congenital hemiparesis. Nineteen participants demonstrating an ipsilesional motor-evoked potential (MEP) were compared with eleven participants showing an absent ipsilesional MEP response. Comparisons of finger tracking accuracy from the affected and less affected hands and ipsilesional/contralesional (I/C) volume ratio for the primary motor cortex (M1) and posterior limb of internal capsule (PLIC) were done using two-sample t-tests. Participants showing an ipsilesional MEP response demonstrated superior tracking performance from the less affected hand (p=0.016) and significantly higher I/C volume ratios for M1 (p=0.028) and PLIC (p=0.005) compared to participants without an ipsilesional MEP response. Group differences in finger tracking accuracy from the affected hand were not significant. These results highlight differentiating factors amongst children with congenital hemiparesis showing contrasting MEP responses: less affected hand performance and preserved M1 and PLIC volume. Along with MEP status, these factors pose important clinical implications in pediatric stroke rehabilitation. These findings may also reflect competitive developmental processes associated with the preservation of affected hand function at the expense of some function in the less affected hand.

Serial treatments of primed low-frequency rTMS in stroke: characteristics of responders vs. nonresponders

PURPOSE

This study analyzed the characteristics of responders vs. nonresponders in people with stroke receiving a novel form of repetitive transcranial magnetic stimulation (rTMS) to improve hand function.

METHODS

Twelve people with stroke received five treatments of 6-Hz primed low-frequency rTMS to the contralesional primary motor area. We compared demographic factors, clinical features, and the ipsilesional/contralesional volume ratio of selected brain regions in those who improved hand performance (N = 7) on the single-hand component of the Test Évaluant la performance des Membres supérieurs des Personnes Âgées (TEMPA) and those who showed no improvement (N = 5).

RESULTS

Responders showed significantly greater baseline paretic hand function on the TEMPA, greater preservation volume of the ipsilesional posterior limb of the internal capsule (PLIC), and lower scores (i.e., less depression) on the Beck Depression Inventory than nonresponders. There were no differences in age, sex, stroke duration, paretic side, stroke hemisphere, baseline resting motor threshold for ipsilesional primary motor area (M1), NIH Stroke Scale, Upper Extremity Fugl-Meyer, Mini-Mental State Examination, or preservation volume of M1, primary somatosensory area, premotor cortex, or supplementary motor area.

CONCLUSION

Our results support that preserved PLIC volume is an important influential factor affecting responsiveness to rTMS.

Safety of primed repetitive transcranial magnetic stimulation and modified constraint-induced movement therapy in a randomized controlled trial in pediatric hemiparesis

OBJECTIVE

To investigate the safety of combining a 6-Hz primed low-frequency repetitive transcranial magnetic stimulation (rTMS) intervention in the contralesional hemisphere with a modified constraint-induced movement therapy (mCIMT) program in children with congenital hemiparesis.

DESIGN

Phase 1 randomized, double-blinded, placebo-controlled pretest/posttest trial.

SETTING

University academic facility and pediatric specialty hospital.

PARTICIPANTS

Subjects (N = 19; age range, 8-17 y) with congenital hemiparesis caused by ischemic stroke or periventricular leukomalacia. No subject withdrew because of adverse events. All subjects included completed the study.

INTERVENTIONS

Subjects were randomized to 1 of 2 groups: either real rTMS plus mCIMT (n = 10) or sham rTMS plus mCIMT (n = 9).

MAIN OUTCOME MEASURES

Adverse events, physician assessment, ipsilateral hand function, stereognosis, cognitive function, subject report of symptoms assessment, and subject questionnaire.

RESULTS

No major adverse events occurred. Minor adverse events were found in both groups. The most common events were headaches (real: 50%, sham: 89%; P = .14) and cast irritation (real: 30%, sham: 44%; P = .65). No differences between groups in secondary cognitive and unaffected hand motor measures were found.

CONCLUSIONS

Primed rTMS can be used safely with mCIMT in congenital hemiparesis. We provide new information on the use of rTMS in combination with mCIMT in children. These findings could be useful in research and future clinical applications in advancing function in congenital hemiparesis.

Pediatric stroke and transcranial direct current stimulation: methods for rational individualized dose optimization

BACKGROUND

Transcranial direct current stimulation (tDCS) has been investigated mainly in adults and doses may not be appropriate in pediatric applications. In perinatal stroke where potential applications are promising, rational adaptation of dosage for children remains under investigation.

OBJECTIVE

Construct child-specific tDCS dosing parameters through case study within a perinatal stroke tDCS safety and feasibility trial.

METHODS

10-year-old subject with a diagnosis of presumed perinatal ischemic stroke and hemiparesis was identified. T1 magnetic resonance imaging (MRI) scans used to derive computerized model for current flow and electrode positions. Workflow using modeling results and consideration of dosage in previous clinical trials was incorporated. Prior ad hoc adult montages vs. de novo optimized montages provided distinct risk benefit analysis. Approximating adult dose required consideration of changes in both peak brain current flow and distribution which further tradeoff between maximizing efficacy and adding safety factors. Electrode size, position, current intensity, compliance voltage, and duration were controlled independently in this process.

RESULTS

Brain electric fields modeled and compared to values previously predicted models (Datta et al., 2011; Minhas et al., 2012). Approximating conservative brain current flow patterns and intensities used in previous adult trials for comparable indications, the optimal current intensity established was 0.7 mA for 10 min with a tDCS C3/C4 montage. Specifically 0.7 mA produced comparable peak brain current intensity of an average adult receiving 1.0 mA. Electrode size of 5 × 7 cm(2) with 1.0 mA and low-voltage tDCS was employed to maximize tolerability. Safety and feasibility confirmed with subject tolerating the session well and no serious adverse events.

CONCLUSION

Rational approaches to dose customization, with steps informed by computational modeling, may improve guidance for pediatric stroke tDCS trials.

Mobility criteria for upright sitting with patients in the neuro/trauma intensive care unit: an analysis of length of stay and functional outcomes

BACKGROUND AND PURPOSE

Few studies have explored optimal advancement and variation in mobility and length of stay (LOS) data with critically ill patients in the intensive care unit (ICU). The purpose of this study was to analyze the outcomes and LOS of critically ill patients in the neurotrauma ICU involved in rehabilitation.

METHODS

A bidirectional case-control study of a total of 30 patients admitted to a level 1 trauma hospital in the metropolitan Chicago area with Glasgow Coma Score (GCS) of ≤12 (3-12) were studied. Functional outcomes of a structured mobility group were compared at first upright sitting and at ICU discharge using the functional independence measure (FIM). Retrospective LOS review of a group (n = 15) with unstructured activity advancement was compared.

RESULTS

The main outcome measures were FIM scores and LOS in number of days. In the structured mobility group, a significant increase in functional performance between first upright sitting and ICU discharge was found (P < .005). Length of stay was shorter in the structured mobility groups but the difference was not statistically significant.

CONCLUSIONS

Results from this study revealed favorable functional outcomes for patients involved in a structured mobility program with physical therapy in the neuro/trauma ICU.

Gross motor outcomes in children with hemiparesis involved in a modified constraint-induced therapy program

OBJECTIVE

Constraint-Induced Therapy (CIT) has been used in pediatric rehabilitation and targets upper extremity (UE) outcomes. The purpose of this study was to measure concurrent gross motor and lower extremity functional changes using the Gross Motor Function Measure (GMFM) before and after a modified UE CIT program. The Assisting Hand Assessment (AHA) was used to evaluate upper extremity outcomes.

DESIGN

Before-after trial design of a 19-day outpatient CIT program at Seattle Children's Hospital in Seattle, WA, USA of six ambulatory children with spastic hemiparesis between the ages of 5 and 11 years with GMFCS scores of 1. GMFM Section D (Standing) and E (Walking, Running, Jumping) and AHA scores were obtained before and after a modified CIT program.

RESULTS

Significant differences were found between pre and post-CIT AHA and GMFM section D and E scores (p < 0.05). All children improved from baseline, yet the child with the lowest initial scores revealed the greatest improvements.

CONCLUSIONS

Improvements in GMFM and AHA scores were noted after a modified CIT program. Such data suggests that CIT may also influence rehabilitation outcomes not only specific to the upper extremity and warrants further investigation.

6-Hz primed low-frequency rTMS to contralesional M1 in two cases with middle cerebral artery stroke

This case study contrasted two subjects with stroke who received 6-Hz primed low-frequency repetitive transcranial magnetic stimulation (rTMS) to the contralesional primary motor area (M1) to disinhibit ipsilesional M1. Functional magnetic resonance imaging (fMRI) showed that the intervention disrupted cortical activation at contralesional M1. Subject 1 showed decreased intracortical inhibition and increased intracortical facilitation following intervention during paired-pulse TMS testing of ipsilesional M1. Subject 2, whose precentral knob was totally obliterated and who did not show an ipsilesional motor evoked potential at pretest, still did not show any at posttest; however, her fMRI did show a large increase in peri-infarct zone cortical activation. Behavioral results were mixed, indicating the need for accompanying behavioral training to capitalize on the brain organization changes induced with rTMS.