Ipsilateral Corticospinal Projections Research Articles

Motor organization of unilateral polymicrogyria associated with ipsilateral brainstem atrophy – a case report

BackgroundPolymicrogyria refers to the disruption of normal cerebral cortical development late in neuronal migration or in early cortical organization. Although patients with polymicrogyria feature relatively favorable motor outcomes, polymicrogyric lesions accompanied by extensive unilateral hemispheric atrophy and ipsilateral brainstem atrophy may induce poorer motor outcomes. This study is the first to employ transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) to characterize changes to motor organization and white matter tracts induced by polymicrogyria.Case presentationWe document a case of a 16-year-old female with left hemiplegic unilateral polymicrogyria associated with ipsilateral brainstem atrophy. Magnetic resonance imaging (MRI) of the brain revealed unilateral polymicrogyria to have affected anterior cortical areas, including the perisylvian region on the right side. The right halves of the brain and brainstem were significantly smaller than the left halves. Although our patient was found to exhibit cortical dysplasia of the right frontoparietal and sylvian fissure areas and a decreased number of fibers in the corticospinal tract (CST) of the affected side on DTI, the connectivity of the CST was preserved up to the motor cortex. We also measured the cross-sectional area of the CST at the level of the pons. In TMS, contralateral motor evoked potentials (MEPs) were evoked from both hands, but the ipsilateral MEPs were evoked only from the left hand. The left hand featured a long duration, polyphasic pattern of contralateral MEPs.Discussion and conclusionTMS revealed that the concurrent bilateral projections to the paretic hand from the affected and unaffected hemispheres and contralateral MEPs in the paretic hand were polyphasic, indicating delayed electrophysiological maturation or a pathologic condition of the corticospinal motor pathways. In DTI, the cross-sectional area of the CST at the level of the pons on the affected side was smaller than that on the unaffected side. These DTI findings reveal an inadequate CST volume. Despite extensive brain malformation and ipsilateral brainstem atrophy, our patient had less severe motor dysfunction and presented with involuntary mirror movements. Mirror movements in the paretic hand are considered to indicate ipsilateral corticospinal projections from the unaffected hemisphere and may suggest favorable motor outcomes in early brain injury.

An Unusual, Intermediate-Sized Lesion Affecting Motor Organization in a Patient With Schizencephaly: A Case Report.

Schizencephalies are abnormal clefts of the cerebral hemispheres that result from abnormal late neuronal migration and cortical organization. In the present study, we report a different type of unusual motor organization in a patient with a schizencephalic cleft in the right hemisphere and polymicrogyria in the opposite hemisphere. Despite similar brain pathology affecting the sensorimotor cortex, motor organization differed from previously known bilateral congenital brain lesions. We conducted a transcranial magnetic stimulation (TMS) and diffusion tensor image (DTI) study to confirm the motor organization. In this case, ipsilateral corticospinal projections to the paretic hands were observed during TMS of the less affected hemisphere, along with polymicrogyria, similar to the previous study. However, a crossed corticospinal tract to the paretic hand from the more severely affected hemisphere was observed in this case-a pattern of motor organization that has yet to be reported in this patient population. Our findings indicate that motor organization after early brain injury may be affected by the interhemispheric competition of the corticospinal system and bilateral brain lesions, thereby resulting in unilateral hemiparesis.

Fatigue in children with perinatal stroke: clinical and neurophysiological associations.

To characterize fatigue in children with hemiparesis with perinatal stroke and explore associations with measures of motor performance and corticospinal excitability. Forty-five children (16 females, 29 males), aged 6 to 18years (mean [SD] 12y [4]), with magnetic resonance imaging-confirmed perinatal stroke participated. Associations between fatigue (Pediatric Quality of Life Inventory Version 3.0 cerebral palsy module fatigue subscale), motor performance (Assisting Hand Assessment [AHA], Box and Blocks Test, grip strength), and excitability of corticospinal projections to both hands were examined using ranked tests of correlation, robust regression, and the Mann-Whitney U test. Nearly half of theparticipants (n=21) reported experiencing fatigue in the previous month. Function in the less affected hand (Box and Blocks Test, grip strength) was correlated with fatigue scores. Participants with preserved ipsilateral projections to the more affected hand had less fatigue, and scores correlated with the excitability of these projections. Fatigue scores were not associated with age, sex, or AHA score. Fatigue is common in children with hemiparesis with perinatal stroke and is associated with motor performance and the presence and excitability of ipsilateral corticospinal projections from the contralesional hemisphere to the more affected hand. Fatigue is common in children with hemiparesis with perinatal stroke. Fatigue was associated with motor performance and strength in the less affected, but not the more affected, hand. Fatigue was associated with the presence and excitability of ipsilateral corticospinal projections from the contralesional hemisphere.

Pre-movement planning processes in people with congenital mirror movements

ObjectivePre-movement processes were investigated in people with Congenital mirrormovement (CMM), a rare disorder in which bilateral movement (mirroring) occurs in the upper distal extremities (primarily the hands and fingers) during intended unilateral movements. Abnormal density of ipsilateral corticospinal projections is an established hallmark of CMM. This study tested whether the Lateralised Readiness Potential (LRP), which reflects movement planning and readiness, is also abnormal in people with CMM. MethodsTwenty-eight neurologically-normal controls and 8 people with CMM were tested on a unimanual Go/No-go task while electroencephalography (EEG) was recorded to assess the LRP. ResultsNo significant group differences were found in reaction time (RT). However, significantly smaller LRP amplitudes were found, on average, in the CMM group compared to Controls at central-motor (C3,C4) sites in stimulus-locked and response-locked epochs; similar group differences were also found at further frontal sites (F3,F4) during response-locked epochs. ConclusionsAbnormal brain activity in pre-movement processes associated with response planning and preparation is present in people with CMM. SignificanceAberrant bilateral activity during pre-movement processes is clearly implicated; whether part of the etiology of CMM, or as a mechanism of neuro-compensation, is not yet known.

Preclinical and Clinical Evidence on Ipsilateral Corticospinal Projections: Implication for Motor Recovery.

Motor impairment is the most common complication after stroke, and recovery of motor function has been shown to be dependent on the extent of lesion in the ipsilesional corticospinal tract (iCST) and activity within ipsilesional primary and secondary motor cortices. However, work from neuroimaging research has suggested a role of the contralesional hemisphere in promoting recovery after stroke potentially through the ipsilateral uncrossed CST fibers descending to ipsilateral spinal segments. These ipsilateral fibers, sometimes referred to as "latent" projections, are thought to contribute to motor recovery independent of the crossed CST. The aim of this paper is to evaluate using cumulative evidence from animal models and human patients on whether an uncrossed CST component is present in mammals and conserved through primates and humans, and whether iCST fibers have a functional role in hemiparetic/hemiplegic human conditions. This review highlights that an ipsilateral uncrossed CST exists in human during development, but the evidence on a functionally relevant iCST component in adult humans is still elusive. In addition, this review argues that whereas activity within the ipsilesional cortex is essential for enhancing motor recovery after stroke, the role of iCST projections specifically is still controversial. Finally, conclusions from current literature emphasize the importance of activity in the ipsilesional cortex and the integrity of crossed CST fibers as major determinants of motor recovery after brain injury.

P019 Ipsilesional and contralesional cortical silent period in pediatric stroke: Preliminary reports

Question The cortical silent period (CSP) is a transient supression of electromyographic (EMG) activity in a pre-activated muscle after a transcranial magnetic stimulation (TMS) pulse. CSP duration reflects intracortical inhibitory mechanisms. Prolonged lesional and shortened non-lesional CSP durations have been associated with poor functional recovery after adult stroke. However, there are few reports regarding CSP duration in children. Our aims is to characterize ipsilesional and contralesional CSP duration in pediatric stroke. Methods Eight children with congenital hemiparesis due to stroke (4 male, age = 11.75 ± 3.26 years) participated. Surface bipolar electrodes were placed over the affected and non-affected first dorsal interosseous (FDI) muscles. TMS single-pulses were delivered using a Magstin 200 stimulator connected to a 70-mm figure of eight coil over the primary motor cortex, bilaterally. Resting motor threshold (RMT) was determined for the FDI. CSP was assessed at 120% RMT during 20% of FDI maximal voluntary contraction. Results Three children presented without an ipsilesional MEP. Ipsilesional RMT average was 64.8% of maximum stimulator output (MSO) (SD = 9.3; range = 53–75) and 56.7% of MSO (SD = 11.6; range = 38–71) for the contralesional hemisphere. Ipsilesional CSP duration was analyzable in one child, x ¯ = 170.5 ms (SD = 11.4; range = 155.5–196.1) and contralesional CSP duration was found in all 8 children, x ¯ = 118.0 ms (SD = 47.3; range = 62.8–174.9) (Fig. 1 Download : Download high-res image (250KB) Download : Download full-size image ). Conclusion Absence of ipsilesional MEPs has been reported in pediatric hemiparesis and could reflect a persistent or enlarged ipsilateral corticospinal tract projections after stroke. Ipsilesional CSP data was largely unanalyzable (no noticeable CSP) with challenges surrounding the ability of the children to sustain paretic FDI contraction, poor motor control (Fig. 2A) and hand spasticity (Fig. 2B Download : Download high-res image (200KB) Download : Download full-size image ). Reports in typically developing children present with shorter CSP duration (25.5–53.8 ms) than adults (150–300 ms). Our results are similar to previous study with pediatric hemiparesis which showed longer CSP duration in ipsilesional and contralesional hemisphere (Mackey et al., 2014). Longer CSP duration could be related to increased activity of inhibitory interneurons in the motor cortex after a perinatal stroke.

Predicting hand function after hemidisconnection.

Hemidisconnections (i.e. hemispherectomies or hemispherotomies) invariably lead to contralateral hemiparesis. Many patients with a pre-existing hemiparesis, however, experience no deterioration in motor functions, and some can still grasp with their paretic hand after hemidisconnection. The scope of our study was to predict this phenomenon. Hypothesizing that preserved contralateral grasping ability after hemidisconnection can only occur in patients controlling their paretic hands via ipsilateral corticospinal projections already in the preoperative situation, we analysed the asymmetries of the brainstem (by manual magnetic resonance imaging volumetry) and of the structural connectivity of the corticospinal tracts within the brainstem (by magnetic resonance imaging diffusion tractography), assuming that marked hypoplasia or Wallerian degeneration on the lesioned side in patients who can grasp with their paretic hands indicate ipsilateral control. One hundred and two patients who underwent hemidisconnections between 0.8 and 36 years of age were included. Before the operation, contralateral hand function was normal in 3/102 patients, 47/102 patients showed hemiparetic grasping ability and 52/102 patients could not grasp with their paretic hands. After hemidisconnection, 20/102 patients showed a preserved grasping ability, and 5/102 patients began to grasp with their paretic hands only after the operation. All these 25 patients suffered from pre- or perinatal brain lesions. Thirty of 102 patients lost their grasping ability. This group included all seven patients with a post-neonatally acquired or progressive brain lesion who could grasp before the operation, and also all three patients with a preoperatively normal hand function. The remaining 52/102 patients were unable to grasp pre- and postoperatively. On magnetic resonance imaging, the patients with preserved grasping showed significantly more asymmetric brainstem volumes than the patients who lost their grasping ability. Similarly, these patients showed striking asymmetries in the structural connectivity of the corticospinal tracts. In summary, normal preoperative hand function and a post-neonatally acquired or progressive lesion predict a loss of grasping ability after hemidisconnection. A postoperatively preserved grasping ability is possible in hemiparetic patients with pre- or perinatal lesions, and this is highly likely when the brainstem is asymmetric and especially when the structural connectivity of the corticospinal tracts within the brainstem is asymmetric.

Hand function assessment in the first years of life in unilateral cerebral palsy: Correlation with neuroimaging and cortico-spinal reorganization.

The purpose of the present study was to correlate early hand function assessment during the first years of life with neuroimaging findings and the different patterns of cortico-motor reorganization in children with unilateral cerebral palsy (UCP). We conducted a long prospective observational study, in which 17 children with UCP (8 left-sided hemiplegia; Manual Ability Classification System level 1-3) were first assessed at a mean age of 24 months (range 18-28), and followed up by means of the Besta Scale, a new standardized protocol assessing both unimanual and bimanual hand function. They also underwent Melbourne Assessment of Unilateral Upper Limb Function (MUUL) and single-pulse Transcranial Magnetic Stimulation (TMS) at a mean age of 10 years 5 months (range 9y 1m-12y 8m). Brain MRIs of all the 17 children were independently assessed and scored by two blinded observers, according to a defined protocol. Possible correlations between hand function at first assessment, neuroimaging and TMS data were analyzed. Early hand function impairment significantly correlated with the extension of brain damage (ρ=-0.531, p=0.028), number of involved areas (ρ=-0.608, p=0.010), presence of radiological signs of cortico-spinal degeneration (ρ=-0.628, p=0.007), and basal ganglia involvement (ρ=-0.485, p=0.049). Additionally, higher hand function scores (i.e. better hand function) at first assessment significantly correlated with contralateral cortico-spinal projections, while lower scores significantly correlated with either mixed or ipsilateral cortico-spinal projections to the affected hand (χ(2)(2)=11.418, p=0.003; post-hoc tests: contralateral TMS group versus ipsilateral: Z=-2.943, p=0.002 and contralateral TMS group versus mixed: Z=-2.775, p=0.006). To our knowledge, this is the first study correlating hand function assessment in the first years of life, and its evolution over time, with neuroimaging and cortico-spinal projection patterns in children with UCP. These findings could contribute to an improved prediction of prognosis and a better delineation of therapeutic interventions in young children with UCP.

Frontal and frontoparietal injury differentially affect the ipsilateral corticospinal projection from the nonlesioned hemisphere in monkey (Macaca mulatta).

Upper extremity hemiplegia is a common consequence of unilateral cortical stroke. Understanding the role of the unaffected cerebral hemisphere in the motor recovery process has been encouraged, in part, by the presence of ipsilateral corticospinal projections (iCSP). We examined the neuroplastic response of the iCSP from the contralesional primary motor cortex (cM1) hand/arm area to spinal levels C5-T1 after spontaneous long-term recovery from isolated frontal lobe injury and isolated frontoparietal injury. High-resolution tract tracing, stereological, and behavioral methodologies were applied. Recovery from frontal motor injury resulted in enhanced numbers of terminal labeled boutons in the iCSP from cM1 compared with controls. Increases occurred in lamina VIII and the adjacent ventral sectors of lamina VII, which are involved in axial/proximal limb sensorimotor processing. Larger frontal lobe lesions were associated with greater numbers of terminal boutons than smaller frontal lobe lesions. In contrast, frontoparietal injury blocked this response; total bouton number was similar to controls, demonstrating that disruption of somatosensory input to one hemisphere has a suppressive effect on the iCSP from the nonlesioned hemisphere. However, compared with controls, elevated bouton numbers occurred in lamina VIII, at the expense of lamina VII bouton labeling. Lamina IX boutons were also elevated in two frontoparietal lesion cases with extensive cortical injury. Because laminae VIII and IX collectively harbor axial, proximal, and distal motoneurons, therapeutic intervention targeting the ipsilateral corticospinal linkage from cM1 may promote proximal, and possibly distal, upper-limb motor recovery following frontal and frontoparietal injury.

Hemispheric Dissociation between Ipsilateral Motor and Contralateral Somatosensory Representation of the Paretic Hand: Deterioration of Hand Function after Hemispherotomy in a Case of Hemispheric Polymicrogyria

Aims: Hemispheric polymicrogyria (HPMG) often causes unilateral spastic cerebral palsy and severe therapy-resistant epilepsy. The most effective treatment regarding seizure freedom is hemispherotomy. Prediction of hand function after hemispherotomy is challenging, as PMG can not only harbor function, but also induce interhemispheric reorganization. Previous studies showed preserved postoperative grasp function when the paretic hand was controlled via ipsilateral corticospinal projections; whether such patients can show a deterioration of hand function is, however, not known.

Vulnerability of the medial frontal corticospinal projection accompanies combined lateral frontal and parietal cortex injury in rhesus monkey.

Concurrent damage to the lateral frontal and parietal cortex is common following middle cerebral artery infarction, leading to upper extremity paresis, paresthesia, and sensory loss. Motor recovery is often poor, and the mechanisms that support or impede this process are unclear. Since the medial wall of the cerebral hemisphere is commonly spared following stroke, we investigated the spontaneous long-term (6 and 12 month) effects of lateral frontoparietal injury (F2P2 lesion) on the terminal distribution of the corticospinal projection (CSP) from intact, ipsilesional supplementary motor cortex (M2) at spinal levels C5 to T1. Isolated injury to the frontoparietal arm/hand region resulted in a significant loss of contralateral corticospinal boutons from M2 compared with controls. Specifically, reductions occurred in the medial and lateral parts of lamina VII and the dorsal quadrants of lamina IX. There were no statistical differences in the ipsilateral CSP. Contrary to isolated lateral frontal motor injury (F2 lesion), which results in substantial increases in contralateral M2 labeling in laminae VII and IX (McNeal et al. [2010] J. Comp. Neurol. 518:586-621), the added effect of adjacent parietal cortex injury to the frontal motor lesion (F2P2 lesion) not only impedes a favorable compensatory neuroplastic response but results in a substantial loss of M2 CSP terminals. This dramatic reversal of the CSP response suggests a critical trophic role for cortical somatosensory influence on spared ipsilesional frontal corticospinal projections, and that restoration of a favorable compensatory response will require therapeutic intervention.

Assessment of the contralesional corticospinal tract in early-onset pediatric hemiplegia: Preliminary findings.

While pediatric hemiplegia results from a unilateral lesion, the immature state of the brain at the time of injury increases the likelihood of observing changes in the non-lesioned hemisphere as well. The purpose of this preliminary study was to use diffusion tensor imaging to evaluate the contralesional corticospinal tracts in individuals with early-onset pediatric hemiplegia. Twelve individuals with pediatric hemiplegia and ten age-matched controls underwent diffusion tensor imaging (DTI). Corticospinal projections were reconstructed using probabilistic tractography for both the lesioned and contralesional side in pediatric hemiplegia as well as the dominant and non-dominant sides in control subjects. The contralesional tract was found to have decreased white matter integrity relative to control subjects. Compared to controls, the contralesional tract also showed increased tract volume. The increase in volume suggests the presence of ipsilateral corticospinal projections from the contralesional hemisphere that are maintained during development to control the paretic extremities. Decreases in integrity may be explained by diffuse damage or incomplete maturation. The findings of this study support the notion of bilateral motor involvement in pediatric hemiplegia, and the need to address bilateral neural changes as well as motor deficits in this population.

Intraoperative brain mapping to identify corticospinal projections during resective epilepsy surgery in children with congenital hemiparesis.

The purpose of the study is to determine corticospinal organization using intraoperative neurophysiologic monitoring (IONM) during resective epilepsy surgery for patients with congenital hemiparesis and intractable epilepsy. Ten patients, aged 3-17, with intractable epilepsy underwent resective surgery. Transcranial stimulation (TCS) was achieved using a pair of cork screws at Cz and C3/C4, respectively. A 1 × 4 stimulating electrode strip was placed on the presumed motor cortex of the affected hemisphere for direct cortical stimulation (DCS) after craniotomy. Multipulse TCS and DCS train stimulation was delivered, with simultaneous recordings from bilateral abductor pollicis brevis and abductor halluces, to determine the corticospinal projection pattern of the paretic limbs. The above mapping techniques revealed ipsilateral corticospinal projections from the contralesional hemisphere to target muscles in the paretic limbs in three patients, projections from both hemispheres to target muscles in three, and preserved crossed projections from the affected hemisphere in four. Nine patients were seizure free after surgery. Five had unchanged postoperative functional status, and three showed minimally improved use of the paretic hand. Two developed new motor deficits after surgery, which may have been due to a premotor syndrome in one patient, since it completely resolved within 2 weeks. The other experienced increased weakness of the paretic lower limb because a small part of the eloquent cortex was removed for better seizure control. Using IONM to define the corticospinal projection pattern is a valuable technique that can potentially replace preoperative fMRI and transcranial magnetic stimulation in resective epilepsy surgery, particularly for younger patients.

Two types of exercise‐induced neuroplasticity in congenital hemiparesis: a transcranial magnetic stimulation, functional MRI, and magnetoencephalography study

Early unilateral brain lesions can lead to a persistence of ipsilateral corticospinal projections from the contralesional hemisphere, which can enable the contralesional hemisphere to exert motor control over the paretic hand. In contrast to the primary motor representation (M1), the primary somatosensory representation (S1) of the paretic hand always remains in the lesioned hemisphere. Here, we report on differences in exercise-induced neuroplasticity between individuals with such ipsilateral motor projections (ipsi) and individuals with early unilateral lesions but 'healthy' contralateral motor projections (contra). Sixteen children and young adults with congenital hemiparesis participated in the study (contralateral [Contra] group: n=7, four females, three males; age range 10-30y, median age 16y; ipsilateral [Ipsi] group: n=9, four females, five males; age range 11-31y, median age 12y; Manual Ability Classification System levels I to II in all individuals in both groups). The participants underwent a 12-day intervention of constraint-induced movement therapy (CIMT), consisting of individual training (2h/d) and group training (8h/d). Before and after CIMT, hand function was tested using the Wolf Motor Function Test (WMFT) and diverging neuroplastic effects were observed by transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG). Statistical analysis of TMS data was performed using the non-parametric Wilcoxon signed-rank test for pair-wise comparison; for fMRI standard statistical parametric and non-parametric mapping (SPM5, SnPM3) procedures (first level/second level) were carried out. Statistical analyses of MEG data involved analyses of variance (ANOVA) and t-tests. While MEG demonstrated a significant increase in S1 activation in both groups (p=0.012), TMS showed a decrease in M1 excitability in the Ipsi group (p=0.036), but an increase in M1 excitability in the Contra group (p=0.043). Similarly, fMRI showed a decrease in M1 activation in the Ipsi group, but an increase in activation in the M1-S1 region in the Contra group (for both groups p<0.001 [SnPM3] within the search volume). Different patterns of sensorimotor (re)organization in individuals with early unilateral lesions show, on a cortical level, different patterns of exercise-induced neuroplasticity. The findings help to improve the understanding of the general principles of sensorimotor learning and will help to develop more specific therapies for different pathologies in congenital hemiparesis.

Interlimb interactions during bilateral voluntary elbow flexion tasks in chronic hemiparetic stroke

The purpose was to systematically investigate interlimb interactions in chronic hemiparetic stroke. Fourteen poststroke hemiparetic subjects (>1 year) performed maximum voluntary contraction (MVC) elbow flexion tasks without visual feedback with one (unilateral) and two limbs simultaneously (bilateral). At submaximal levels, subjects produced force to a visual target reflecting 20%, 40%, 60%, and 80% of corresponding MVC in unilateral tasks, and of summated unilateral MVCs in bilateral tasks. Elbow flexion force and biceps surface electromyogram (EMG) were measured bilaterally. Proportionally increased EMG activity on the contralateral limb (motor overflow) was observed during unilateral tasks of the nonimpaired limb but not of the impaired limb. During bilateral tasks at submaximal levels, the impaired limb produced less force (i.e., force deficit [FD]) as compared to expected forces based upon its unilateral MVC. Force deficit on the impaired limb was compensated by greater force production on the nonimpaired limb such that the visual target was reached. However, force contribution to the total force progressively decreased from the nonimpaired side, when the level of submaximal contractions increased. During bilateral MVC tasks, there was no FD on the impaired limb, but FD was observed on the nonimpaired limb. A net result of a small bilateral deficit in force with parallel changes in EMG was observed. These novel findings of activation level–dependent interactions and asymmetrical contralateral motor overflow provide new insights that, among other compensatory mechanisms, ipsilateral corticospinal projections from the nonlesioned hemisphere play an important role in interlimb interactions in chronic stroke, in addition to unbalanced interhemispheric inhibition.

Neonatal neuroimaging predicts recruitment of contralesional corticospinal tracts following perinatal brain injury

Unilateral perinatal brain injury may result in recruitment of ipsilateral projections originating in the unaffected hemisphere and development of unilateral spastic cerebral palsy (USCP). The aim of this study was to assess the predictive value of neonatal neuroimaging following perinatal brain injury for recruitment of ipsilateral corticospinal tracts. Neonatal magnetic resonance imaging (MRI) and cranial ultrasound scans of 37 children (20 males, 17 females; median [range] gestational age 36 wks(+4) [26(+6) -42wks(+5) ] and birthweight 2312 g ([770-5230g]) with unilateral perinatal arterial ischaemic stroke (n=23) or periventricular haemorrhagic infarction (n=14) were reviewed and scored for involvement of the corticospinal trajectory. Hand function was assessed using the Assisting Hand Assessment (AHA) and transcranial magnetic stimulation (TMS) was performed (age range 7y 4mo-18y and 7mo) to determine the type of cortical motor organization (normal, mixed or ipsilateral). Neuroimaging scores were used to predict TMS patterns. Eighteen children developed USCP with ipsilateral corticospinal tract projections in 13 children (eight mixed, five ipsilateral). AHA scores decreased with increased ipsilateral projections. Asymmetry of the corticospinal tracts seen on neonatal MRI was predictive of development of USCP and recruitment of ipsilateral tracts (positive and negative predictive value of 73% and 91%). Neonatal neuroimaging can predict recruitment of ipsilateral corticospinal tracts. Early knowledge of the expected pattern of cortical motor organization will allow early identification of children eligible for early therapy.

Ipsilateral Motor Control Without Mirror Movements?

Aims: Some children with unilateral-spastic cerebral palsy (=congenital hemiparesis) control their paretic hands via ipsilateral cortico-spinal projections from the contra-lesional hemisphere, which, in these cases, therefore controls both hands. This is typically associated with mirror movements both during voluntary unimanual movements of the paretic and of the non-paretic hand. It is still unclear, however, whether ipsilateral motor control can also exist without mirror movements. Methods: A former term-born child with congenital hemiparesis due to unilateral white matter damage probably resulting from intrauterine periventricular hemorrhage with venous infarction and therapy-refractory epilepsy received hemispherotomy at the age of 5 years. Results: Postoperatively, the paretic hand was still able to grasp; neurological examination at the age of 9 years showed no mirror movements despite (obvious) unihemispheric motor control of both hands. Conclusion: Since transcranial magnetic stimulation has not yet been performed in this patient, there is no formal proof for the existence of ipsilateral cortico-spinal projections from the contra-lesional hemisphere to the paretic hand. The preserved grasp function after hemispherotomy, however, is highly suggestive. Therefore, this case report demonstrates that at least in some children with ipsilateral motor control, the contra-lesional hemisphere can control both hands independently from each other, so that no mirror movements occur. Thus, the absence of mirror movements is not a valid sign for contralateral motor control; this question still requires transcranial magnetic stimulation.

Human hand function: the limitations of brain and brawn

Human hand function: the limitations of brain and brawn

Differential contributions of rostral and caudal frontal forelimb areas to compensatory process after neonatal hemidecortication in rats

Following brain damage, especially in juvenile animals, large-scale reorganization is known to occur in the remaining brain structures to compensate for functional deficits. In rats with neonatal hemidecortication, corticospinal fibers originating from the undamaged side of the sensorimotor cortex issue collateral sprouts to the ipsilateral spinal gray matter that mediate cortical excitation to ipsilateral forelimb motoneurons and compensate for the deficit in forelimb movements. The present study was designed to investigate the origins of the ipsilateral corticospinal projection in neonatally hemidecorticated rats. Corticospinal neurons (CSNs) were labeled in adults by injecting retrograde neural tracers, cholera toxin subunit B with different fluorescent probes, into either side of the cervical spinal gray matter. In the undamaged cortex, double-labeled neurons were rarely found. CSNs with contralateral projections (contra-CSNs) and those with ipsilateral projections (ipsi-CSNs) were distributed both in the rostral forelimb motor area (RFA) and the caudal forelimb motor area (CFA). However, there was a difference in the distributions of the ipsi-CSNs between the two forelimb areas. Whereas the distribution of the ipsi-CSNs largely overlapped with that of the contra-CSNs in the RFA, the ipsi-CSNs tended to be segregated from the contra-CSNs in the CFA. The results suggested that the RFA and the CFA contribute to the compensatory process in different ways.

What Has Transcranial Magnetic Stimulation Taught Us About Neural Adaptations To Strength Training? A Brief Review

The evidence for neural mechanisms underpinning rapid strength increases has been investigated and discussed for over 30 years using indirect methods, such as surface electromyography, with inferences made toward the nervous system. Alternatively, electrical stimulation techniques such as the Hoffman reflex, volitional wave, and maximal wave have provided evidence of central nervous system changes at the spinal level. For 25 years, the technique of transcranial magnetic stimulation (TMS) has allowed for noninvasive supraspinal measurement of the human nervous system in a number of areas such as fatigue, skill acquisition, clinical neurophysiology, and neurology. However, it has only been within the last decade that this technique has been used to assess neural changes after strength training. The aim of this brief review is to provide an overview of TMS, discuss specific strength training studies that have investigated changes, after short-term strength training in healthy populations in upper and lower limbs, and conclude with further research suggestions and the application of this knowledge for the strength and conditioning coach.