Patrick Ciechanski

Transcranial Direct-Current Stimulation Can Enhance Motor Learning in Children

&NA; This study aims to determine the effects of transcranial direct‐current stimulation (tDCS) on motor learning in healthy school‐aged children. Safety, tolerability, and translation of effects to untrained tasks were also explored. We recruited 24 right‐handed children for a randomized, sham‐controlled, double‐blinded trial to receive: right primary motor cortex (M1) 1 mA anodal (1A‐tDCS), left M1 1 mA cathodal (1C‐tDCS), left M1 2 mA cathodal tDCS (2C‐tDCS), or sham tDCS over 3 consecutive days of motor task practice. Participants trained their left hand to perform the Purdue Pegboard Test (PPT) during tDCS application. Right hand and bimanual PPT, the Jebsen‐Taylor Test (JTT), and the Serial Reaction Time Task (SRTT) were tested at baseline and post‐training. All measures were retested 6 weeks later. Active tDCS montages enhanced motor learning compared with sham (all P < 0.002). Effects were sustained at 6 weeks. Effect sizes were large and comparable across montages: contralateral 1A‐tDCS (Cohens d = 2.58) and ipsilateral 1C‐tDCS (3.44) and 2C‐tDCS (2.76). Performance in the untrained hand PPT, bilateral JTT, and SRTT often improved with tDCS. tDCS was well‐tolerated and safe with no adverse events. These first principles will advance the pairing of tDCS with therapy to enhance rehabilitation for disabled children such as those with cerebral palsy.

Contralesional Corticomotor Neurophysiology in Hemiparetic Children With Perinatal Stroke: Developmental Plasticity and Clinical Function.

Background. Perinatal stroke causes most hemiparetic cerebral palsy. Ipsilateral connections from nonlesioned hemisphere to affected hand are common. The nonlesioned primary motor cortex (M1) determines function and is a potential therapeutic target but its neurophysiology is poorly understood. Objective. We aimed to characterize the neurophysiological properties of the nonlesioned M1 in children with perinatal stroke and their relationship to clinical function. Methods. Fifty-two participants with hemiparetic cerebral palsy and magnetic resonance imaging–confirmed perinatal stroke and 40 controls aged 8 to 18 years completed the same transcranial magnetic stimulation (TMS) protocol. Single-pulse TMS to nonlesioned M1 determined rest and active motor thresholds (RMT/AMT), motor-evoked potential (MEP) latencies, and stimulus recruitment curves (SRC: 100%-150% RMT). Paired-pulse TMS evaluated short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF). Ipsilateral (IP) participants (ipsilateral MEP ≥0.05 mV in ≥5/20 trials) were compared with contralateral MEP only, nonipsilateral (NI) participants. Assisting Hand and Melbourne assessments quantified clinical function. Results. Twenty-five IP were compared with 13 NI (n = 38, median age 12 years, 66% male). IP had lower motor function. SRC to unaffected hand were comparable between IP and NI while IP had smaller ipsilateral SRC. Ipsilateral MEP latencies were prolonged (23.5 ± 1.8 vs 22.2 ± 1.5 ms contra, P < .001). Contralateral SICI was different between IP (−42%) and NI (−20%). Ipsilateral SICI was reduced (−20%). Contralateral ICF was comparable between groups (+43%) and ipsilaterally (+43%). Measures correlated between contralateral and ipsilateral sides. Conclusion. Neurophysiology of nonlesioned M1 and its relationship to motor function is measureable in children with perinatal stroke. Correlation of excitability and intracortical circuitry measures between contralateral and ipsilateral sides suggests common control mechanisms.

Developmental profile of motor cortex transcallosal inhibition in children and adolescents

Transcallosal fibers facilitate interhemispheric networks involved in motor tasks. Despite their clinical relevance, interhemispheric motor control systems have not been completely defined in the developing brain. The objective of this study was to examine the developmental profile of transcallosal inhibition in healthy children and adolescents. Nineteen typically developing right-handed participants were recruited. Two transcranial magnetic stimulation (TMS) paradigms assessed transcallosal inhibition: ipsilateral silent periods (iSP) and paired-pulse interhemispheric inhibition (IHI). TMS was applied to the motor hotspot of the first dorsal interosseous muscle. Resting motor threshold (RMT), iSP latency, duration and suppression strength, and paired-pulse IHI were measured from both hemispheres. The Purdue Pegboard Test assessed unimanual motor function. Hemispheric differences were evident for RMT and iSP latency and suppression strength, where the left hemisphere had a lower RMT, prolonged latency, and greater suppression strength. iSP duration showed hemispheric symmetry. RMT and iSP latency decreased with age, whereas iSP suppression strength increased. Girls showed shorter iSP latency. Children typically displayed IHI, although hemispheric differences were observed. iSP suppression strength was uniquely associated with IHI within individuals. iSP duration correlated with motor performance. TMS can characterize transcallosal inhibition in normal children and adolescents with effects of age, directionality, sex, and motor performance. Establishing this developmental profile of interhemispheric interactions may advance understanding and therapeutic strategies for pediatric motor disorders such as cerebral palsy.NEW & NOTEWORTHY Here we demonstrate that transcranial magnetic stimulation can characterize transcallosal inhibition in normal children and adolescents with effects of age, directionality, handedness, and motor performance. Interestingly, we also demonstrated sex effects, possibly related to the differing developmental profiles of boys and girls. Establishing this developmental profile of interhemispheric interactions may advance understanding and therapeutic strategies for pediatric motor disorders such as cerebral palsy.

Effects of Transcranial Direct-Current Stimulation on Neurosurgical Skill Acquisition: A Randomized Controlled Trial

BACKGROUND Recent changes in surgical training environments may have limited opportunities for trainees to gain proficiency in skill. Complex skills such as neurosurgery require extended periods of training. Methods to enhance surgical training are required to overcome duty-hour restrictions, to ensure the acquisition of skill proficiency. Transcranial direct-current stimulation (tDCS) can enhance motor skill learning, but is untested in surgical procedural training. We aimed to determine the effects of tDCS on simulation-based neurosurgical skill acquisition. METHODS Medical students were trained to acquire tumor resection skills using a virtual reality neurosurgical simulator. The primary outcome of change in tumor resection was scored at baseline, over 8 repetitions, post-training, and again at 6 weeks. Participants received anodal tDCS or sham over the primary motor cortex. Secondary outcomes included changes in brain resected, resection effectiveness, duration of excessive forces (EF) applied, and resection efficiency. Additional outcomes included tDCS tolerability. RESULTS Twenty-two students consented to participate, with no dropouts over the course of the trial. Participants receiving tDCS intervention increased the amount of tumor resected, increased the effectiveness of resection, reduced the duration of EF applied, and improved resection efficiency. Little or no decay was observed at 6 weeks in both groups. No adverse events were documented, and sensation severity did not differ between stimulation groups. CONCLUSIONS The addition of tDCS to neurosurgical training may enhance skill acquisition in a simulation-based environment. Trials of additional skills in high-skill residents, and translation to nonsimulated performance are needed to determine the potential utility of tDCS in surgical training.

Interhemispheric motor interactions in hemiparetic children with perinatal stroke: Clinical correlates and effects of neuromodulation therapy

OBJECTIVE Brain stimulation and constraint therapy may enhance function after perinatal stroke but mechanisms are unknown. We characterized interhemispheric interactions (IHI) in hemiparetic children and explored their relationship to motor function and neuromodulation. METHODS Forty-five hemiparetic perinatal stroke subjects aged 6-19 years completed a clinical trial of repetitive-transcranial magnetic stimulation (rTMS) and constraint therapy. Paired-pulse TMS measured IHI in cases and normal controls. Suprathreshold conditioning stimuli preceded contralateral test stimuli bidirectionally: stroke to non-stroke (SNS) and non-stroke to stroke (NSS). Primary outcome was the interhemispheric ratio (IHR) between conditioned and test only MEP amplitudes X100 (<100 implied inhibition). Motor outcomes at baseline and post-intervention were compared to IHR. RESULTS Procedures were well tolerated. IHI occurred bidirectionally in controls. Eighteen stroke participants had complete data. IHR were increased in stroke participants in both directions. SNS IHR was >100 (facilitation) in 39% of measurements and correlated with better motor function. NSS IHR correlated with poorer motor function. Intervention-induced clinical change was not associated with IHR. CONCLUSIONS Interhemispheric interactions are altered and related to clinical function, but not necessarily neuromodulation, in children with perinatal stroke. SIGNIFICANCE Adding interhemispheric interactions to evolving models of developmental plasticity following early injury may advance neuromodulation strategies.

Modeling Transcranial Direct-Current Stimulation-Induced Electric Fields in Children and Adults

Transcranial direct-current stimulation (tDCS) is a form of non-invasive brain stimulation that induces electric fields in neuronal tissue, modulating cortical excitability. Therapeutic applications of tDCS are rapidly expanding, and are being investigated in pediatrics for various clinical conditions. Anatomical variations are among a host of factors that influence the effects of tDCS, and pronounced anatomical differences between children and adults suggest that induced electric fields may be substantially different across development. The aim of this study was to determine the strength and distribution of tDCS-induced electric fields across development. Typically developing children, adolescents, and adults were recruited. Individualized finite-element method modeling of primary motor cortex (M1) targeting tDCS was performed. In the largest pediatric sample to date, we found significantly higher peak and mean M1 electric field strength, and more expansive electric field spread for children compared to adults. Electric fields were often comparable between adolescents and adults. Our results suggest that these differences may be associated with age-related differences in skull and extra-axial space thickness, as well as developmental changes occurring in gray and white matter. Individualized current modeling may be a valuable tool for personalizing effective doses of tDCS in future pediatric clinical trials.

Effects of transcranial direct-current stimulation on laparoscopic surgical skill acquisition

Changes in medical education may limit opportunities for trainees to gain proficiency in surgical skills. Transcranial direct‐current stimulation (tDCS) can augment motor skill learning and may enhance surgical procedural skill acquisition. The aim of this study was to determine the effects of tDCS on simulation‐based laparoscopic surgical skill acquisition.

P034 Lesioned motor cortex neurophysiology in children with perinatal stroke

Introduction Perinatal stroke (PS) causes most hemiparetic cerebral palsy. Motor recovery is highly dependent on developmental plasticity in bilateral motor cortex. The fundamental neurophysiology of the lesioned motor cortex (M1) is poorly understood. Objective To characterize lesioned corticomotor neurophysiological properties in hemiparetic children with perinatal stroke. Methods Children 6–18years with MRI-confirmed PS and hemiparesis were recruited (Alberta Perinatal Stroke Project). Transcranial magnetic stimulation (TMS) protocols applied to the lesioned M1 measured rest and active motor thresholds (RMT/AMT) and stimulus response curves (SRC:100-150RMT). Paired-pulse TMS explored short-latency intracortical inhibition and intracortical facilitation (SICI/ICF; 2/10ms ISI). Measures were compared to the non-lesioned hemisphere and healthy controls ( n =40, median 12.2years, range 8–18). Motor outcomes by blinded occupational therapists were Assisting Hand (AHA), Melbourne (MA) assessments and Box and Block (BB). Safety and tolerability were assessed. Results Of 45 children (median 11.3years, 25 male; 65% arterial, 35% PVI), TMS of lesioned M1 evoked contralateral MEPs in only 12 (27%). No ipsilateral MEPs were recorded. Thresholds for evoking a stroke-side MEP were higher than the non-lesioned side ( p =0.04).The s-shaped SRC indicated that the morphology and responsiveness to increases in TMS intensities was preserved but shifted down compared to non-lesioned side or controls contralateral SRC. Contralateral SICI (−39.2%, −42.1%) and ICF (42.5%, 43.6%) effects were comparable between lesioned and non-lesioned sides ( p =0.43, p =0.54, respectively), as well as controls SICI ( p =0.30) and ICF ( p =0.22). Latencies of MEPs from the lesion side (24.3ms) were longer than contralateral, non-lesioned MEP (24.3ms versus 21.6ms, p =0.003). The area under the SRC curve is correlated with all AHA ( r =0.9, p =0.01), MEL ( r =0.9, p =0.02) and BB ( r =0.8, p =0.05). Protocols were well tolerated with no adverse events. Conclusion Cortical physiology of contralateral projections from the lesion side can be measured in hemiparetic children with PS using TMS. Individualized neurophysiology will further inform recently demonstrated therapeutic neuromodulation interventions in this population.