Corticospinal Tract In Children Research Articles

Transcranial magnetic stimulation in assessing the functional capacity of the corticospinal tract in children

Transcranial magnetic stimulation in assessing the functional capacity of the corticospinal tract in children

Surgical treatment of hemispheric and subcortical gliomas adjacent to corticospinal tract in children using MR tractography and intraoperative electrophysiological monitoring

Difficult total resection of supratentorial gliomas adjacent to the corticospinal tract (CST) is due to the high risk of its injury and disability of patients. The main methods for preventing intraoperative CST damage are preoperative MR tractography and intraoperative electrophysiological monitoring. The problem of total resection of gliomas adjacent to the CST with preservation of high functional status is difficult due to immaturity and plasticity of brain structures in children. Moreover, the advantages of MR tractography combined with intraoperative monitoring have not been described. The authors present surgical treatment of supratentorial gliomas adjacent to the CST at different anatomical levels. Patients underwent preoperative and postoperative MR tractography and intraoperative electrophysiological monitoring. MR tractography provided preoperative data on CST lesion. Intraoperative monitoring made it possible to identify and preserve CST in the depth of surgical wound. MR tractography and intraoperative electrophysiological monitoring increase resection quality in patients with hemispheric and subcortical gliomas without postoperative functional deterioration.

Evaluating the Effects of 5-Hz Repetitive Transcranial Magnetic Stimulation With and Without Wrist-Ankle Acupuncture on Improving Spasticity and Motor Function in Children With Cerebral Palsy: A Randomized Controlled Trial.

Objective: The goal of this study is to explore the effect of wrist-ankle acupuncture combined with 5-Hz repetitive transcranial magnetic stimulation (rTMS) on improving spastic state and motor function of children with spastic cerebral palsy by measuring electrophysiological parameters and behaviors.Methods: Twenty-five children with spastic cerebral palsy were enrolled in a single-blind and randomized controlled trial. The control group received 20 sessions of 5-Hz rTMS over the affected hemisphere with 1,000 pulses. The experimental group was given wrist-ankle acupuncture on the basis of the control group. Gross motor function measure (GMFM-66), muscle tension, and electrophysiological parameters of the two groups were assessed at baseline and after intervention.Results: After treatment, the GMFM-66 scores in the same groups were significantly improved (p < 0.001). Besides, the R-value of soleus, gastrocnemius, and hamstring muscle decreased (p < 0.05), and the results showed a trend of shortening MEP latency, increasing amplitude and duration (p < 0.05). Compared to the controlled group, the experimental group displayed more excellent changes in the GMFM-66 scores and motor evoked potential (MEP) latency. The statistical results showed that the increase of GMFM-66 score and the shortening of MEP latency in the experimental group were greater than that in the control group (p < 0.05). However, no significant differences were found in the assessment of muscle tension, amplitude, and duration of MEPs between two groups (p > 0.05).Conclusion: Wrist-ankle acupuncture combined with 5-Hz rTMS is optimal to improve gross motor function and enhance the conductivity of corticospinal tract in children with cerebral palsy but cannot highlight its clinical superiority in improving spasticity.Clinical Trial Registration: [http://www.chictr.org.cn/index.aspx], identifier [chictr2000039495].

Neurodevelopmental impairment is associated with altered white matter development in a cohort of school-aged children born very preterm

Individuals born very preterm (<32 weeks gestation) have altered brain growth and white matter maturation relative to their full-term peers, and approximately 30% will experience neurodevelopmental impairment. We investigated the relationship between neurodevelopmental impairment and MRI measures of white matter microstructure and brain volume.Children born before 30 weeks’ gestation or who had very low birthweight (< 1500 g) underwent neurodevelopmental assessment and MRI at age 7 years as part of the PIANO study, a New Zealand-based cohort study. Fractional anisotropy (FA) and diffusivity measures were derived from diffusion tensor imaging to index white matter microstructure. Volumes were derived from T1-weighted imaging. Neurodevelopmental impairment was defined as a score < 85 on the Wechsler Intelligence Scale for Children, <5th centile on the Movement Assessment Battery for Children or a diagnosis of cerebral palsy by a paediatrician. Relationships between MRI and neurodevelopmental impairment were assessed with general linear models adjusted for sex, gestational age at birth, birthweight z-score, age at assessment, New Zealand Deprivation index score and multiplicity.Children with neurodevelopmental impairment (n = 38) had smaller total brain, cortical grey matter and cerebral white matter volumes compared to children without neurodevelopmental impairment (n = 62) (p < 0.05, false discovery rate corrected), but the regional volume differences did not remain significant after adjustment for total brain volume. Lower FA and higher radial diffusivity were observed in the superior longitudinal fasciculi, uncinate fasciculi and right hemisphere corticospinal tract in children with neurodevelopmental impairment. This may reflect differences in cellular properties such as myelination or axonal packing. Neurodevelopmental impairment may reflect smaller overall brain volume and altered microstructure in white matter tracts that are important for language, cognitive and motor functioning.

Gross Total Resection of Pediatric Cervical Intramedullary Ependymoma with D-Wave Monitoring: A Case Report

Intramedullary spinal cord tumors (IMSCTs) are treated with gross total resection (GTR) for favorable long-term outcome. Monitoring of D-waves in combination with motor evoked potentials (MEPs) minimizes risk of permanent injury to the spinal cord. We present the case of an 8-year-old female with cervical intramedullary ependymoma, an uncommon IMSCT in children. Though > 50% decrement in amplitude of MEPs was noted intraoperatively, D-waves remained stable and GTR of the tumor was thus continued. Despite an immature corticospinal tract in children, we recommend monitoring of D-waves in addition to MEPs to ensure safe GTR of an IMSCT.

Understanding motor difficulties in children with ADHD: A fixel-based analysis of the corticospinal tract

AimsChildren with attention deficit hyperactivity disorder (ADHD) often present with deficits in fine motor control. The cortico-spinal tract (CST) is critical for voluntary motor control. Although neuroimaging work has identified anomalous microstructural properties in the CST in ADHD, no study to date has attempted to investigate the link between deficits in fine motor performance and microstructural properties of the CST in children with ADHD. This study aimed to address this gap using a novel fixel-based analysis (FBA). MethodsParticipants were 50 right-handed medication naïve children with a history of ADHD and 56 non-ADHD controls aged 9–11 years. Fine motor control was assessed using the Grooved Pegboard task. Children underwent high angular resolution diffusion MRI. Following pre-processing, FBA was performed and the semi-automated deep-learning TractSeg was used to delineate the CST bilaterally. Fibre density (FD), fibre cross-section (FC-log), and fibre density/cross-section (FDC) were extracted for each tract. ResultsChildren with ADHD performed significantly worse than non-ADHD children on the Grooved Pegboard task when using their non-dominant hand. They also demonstrated widespread significantly lower diffusion metrics in both CSTs compared to non-ADHD controls. However, no correlations were observed between Grooved Pegboard performance and diffusion metrics for the CST in either hemisphere. ConclusionsWhile we failed to detect a significant relationship between fine motor skill and FBA metrics in either group, this paper extends previous work by showing that children with ADHD and reduced fine motor competence demonstrate atypical microstructure within the CST relative to non-ADHD controls.

White matter characteristics of motor, sensory and interhemispheric tracts underlying impaired upper limb function in children with unilateral cerebral palsy.

This study explored the role of lesion timing (periventricular white matter versus cortical and deep grey matter lesions) and type of corticospinal tract (CST) wiring pattern (contralateral, bilateral, ipsilateral) on white matter characteristics of the CST, medial lemniscus, superior thalamic radiations and sensorimotor transcallosal fibers in children with unilateral cerebral palsy (CP), and examined theassociation with upper limb function. Thirty-four children (mean age 10 years 7 months ± 2 years 3 months) with unilateral CP underwent a comprehensive upper limb evaluation and diffusion weighted imaging (75 directions, b value 2800). Streamline count, fractional anisotropy and mean diffusivity were extracted from the targeted tracts and asymmetry indices were additionally calculated. Transcranial magnetic stimulation was applied to assess the CST wiring pattern. Results showed a more damaged CST in children with cortical and deep grey matter lesions (N = 10) and ipsilateral CST projections (N = 11) compared to children with periventricular white matter lesions (N = 24; p < 0.02) and contralateral CST projections (N = 9; p < 0.025), respectively. Moderate to high correlations were found between diffusion metrics of the targeted tracts and upper limb function (r = 0.45-0.72; p < 0.01). Asymmetry indices of the CST and sensory tracts could best explain bimanual performance (74%, p < 0.0001) and unimanual capacity (50%, p = 0.004). Adding lesion timing and CST wiring pattern did not further improve the model of bimanual performance, while for unimanual capacity lesion timing was additionally retained (58%, p = 0.0002). These results contribute to a better understanding of the underlying neuropathology of upper limb function in children with unilateral CP and point towards a clinical potential of tractography.

Quantitative tractography reveals changes in the corticospinal tract in drug-naïve children with attention-deficit/hyperactivity disorder

The specific role of the corticospinal tract with respect to inattention and impulsive symptoms in children with attention-deficit/hyperactivity disorder (ADHD) has been explored in the past. However, to our knowledge, no study has identified the exact regions of the corticospinal tract that are affected in ADHD. We aimed to determine comprehensive alterations in the white matter microstructure of the corticospinal tract and underlying neuropsychological substrates in ADHD. We recruited 38 drug-naïve children with ADHD and 34 typically developing controls. We employed a tract-based quantitative approach to measure diffusion parameters along the trajectory of the corticospinal tract, and we further correlated alterations with attention and response inhibition measures. Compared with controls, children with ADHD demonstrated significantly lower fractional anisotropy and higher radial diffusivity at the level of cerebral peduncle, and higher fractional anisotropy at the level of the posterior limb of the internal capsule in the right corticospinal tract only. As well, increased fractional anisotropy in the posterior limb of the internal capsule was negatively correlated with continuous performance test attention quotients and positively correlated with reaction time on the Stroop Colour–Word Test; increased radial diffusivity in the right peduncle region was positively correlated with omissions in the Stroop test. The sample size was relatively small. Moreover, we did not consider the different subtypes of ADHD and lacked sufficient power to analyze subgroup differences. Higher-order diffusion modelling is needed in future white matter studies. We demonstrated specific changes in the right corticospinal tract in children with ADHD. Correlations with measures of attention and response inhibition underscored the functional importance of corticospinal tract disturbance in ADHD.

Maturation of Corticospinal Tracts in Children With Hemiplegic Cerebral Palsy Assessed by Diffusion Tensor Imaging and Transcranial Magnetic Stimulation.

Aim: To assess changes in the developmental trajectory of corticospinal tracts (CST) maturation in children with hemiplegic cerebral palsy (HCP).Methods: Neuroimaging data were obtained from 36 children with HCP for both the more affected (MA) and less affected (LA) hemispheres, and, for purposes of direct comparison, between groups, 15 typically developing (TD) children. With diffusion tensor imaging (DTI), we estimated the mean fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) of the corticospinal tract, parameters indicative of factors including myelination and axon density. Transcranial magnetic stimulation (TMS) was performed as a neurophysiologic measure of corticospinal tract integrity and organization. Resting motor threshold (rMT) was obtained per hemisphere, per patient.Results: We observed a significant AD and MD developmental trajectory, both of which were inversely related to age (decrease in AD and diffusivity corresponding to increased age) in both hemispheres of TD children (p < 0.001). This maturation process was absent in both MA and LA hemispheres of children with HCP. Additionally, the TMS-derived previously established rMT developmental trajectory was preserved in the LA hemisphere of children with HCP (n = 26; p < 0.0001) but this trajectory was absent in the MA hemisphere.Conclusions: Corticospinal tract maturation arrests in both hemispheres of children with HCP, possibly reflecting perinatal disruption of corticospinal tract myelination and axonal integrity.

The plasticity of the corticospinal tract in children with obstetric brachial plexus palsy after Botulinum Toxin A treatment

Botulinum neurotoxin A (BTX-A) intervention has long-term benefits for children with obstetric brachial plexus palsy (OBPP). Although cortical plasticity has been widely studied, plasticity in white matter has not received as much attention. Here, six children with OBPP underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) before and 6 months after BTX-A treatment. Surface electromyography (EMG) was recorded. The aim was to investigate changes in the corticospinal tract (CST) as an example longitudinal observation of white matter plasticity. Deterministic fiber tracking with a Fiber Assignment by Continuous Tracking algorithm was used to reconstruct the CST. Fiber tracts passing through a region of interest (ROI) in the posterior limb of the internal capsule and a target ROI in the upper-limb representation of M1 (defined by task-related fMRI) were selected as the CST. Motor performances were improved while EMG showed no significant difference 6 months after the treatment. We observed a significant increase in mean fractional anisotropy and a significant decrease in fiber number after treatment. We analyzed the correlations between DTI metrics and clinical motor assessments. Although the correlation results were not statistically significant, they support the notion that BTX-A treatment causes white matter plasticity and has a positive long-term outcome. Peripheral deafferentation may lead to altered information flow, resulting in the positive adaptation of white matter. This study provides novel insight into cerebral plasticity following peripheral nerve regeneration and indicates that a combination of relatively non-invasive therapies can accelerate plasticity of sensorimotor circuits and promote functional recovery in OBPP.

Diffusion Tractography Biomarkers of Pediatric Cerebellar Hypoplasia/Atrophy: Preliminary Results Using Constrained Spherical Deconvolution.

Advances in MR imaging modeling have improved the feasibility of reconstructing crossing fibers, with increasing benefits in delineating angulated tracts such as cerebellar tracts by using tractography. We hypothesized that constrained spherical deconvolution-based probabilistic tractography could successfully reconstruct cerebellar tracts in children with cerebellar hypoplasia/atrophy and that diffusion scalars of the reconstructed tracts could differentiate pontocerebellar hypoplasia, nonprogressive cerebellar hypoplasia, and progressive cerebellar atrophy. Fifteen children with cerebellar ataxia and pontocerebellar hypoplasia, nonprogressive cerebellar hypoplasia or progressive cerebellar atrophy and 7 controls were included in this study. Cerebellar and corticospinal tracts were reconstructed by using constrained spherical deconvolution. Scalar measures (fractional anisotropy and mean, axial and radial diffusivity) were calculated. A general linear model was used to determine differences among groups for diffusion MR imaging scalar measures, and post hoc pair-wise comparisons were performed. Cerebellar and corticospinal tracts were successfully reconstructed in all subjects. Significant differences in diffusion MR imaging scalars were found among groups, with fractional anisotropy explaining the highest variability. All groups with cerebellar pathologies showed lower fractional anisotropy compared with controls, with the exception of cerebellar hypoplasia. This study shows the feasibility of constrained spherical deconvolution to reconstruct cerebellar and corticospinal tracts in children with morphologic cerebellar pathologies. In addition, the preliminary results show the potential utility of quantitative analysis of scalars of the cerebellar white matter tracts in children with cerebellar pathologies such as cerebellar hypoplasia and atrophy. Further studies with larger cohorts of patients are needed to validate the clinical significance of our preliminary results.

Novel diffusion tensor imaging technique reveals developmental streamline volume changes in the corticospinal tract associated with leg motor control.

Diffusion tensor imaging (DTI) has expanded our knowledge of corticospinal tract (CST) anatomy and development. However, previous developmental DTI studies assessed the CST as a whole, overlooking potential differences in development of its components related to control of the upper and lower extremities. The present cross-sectional study investigated age-related changes, side and gender differences in streamline volume of the leg- and hand-related segments of the CST in children. DTI data of 31 children (1-14 years; mean age: 6±4 years; 17 girls) with normal conventional MRI were analyzed. Leg- and hand-related CST streamline volumes were quantified separately, using a recently validated novel tractography approach. CST streamline volumes on both sides were compared between genders and correlated with age. Higher absolute streamline volumes were found in the left leg-related CST compared to the right (p=0.001) without a gender effect (p=0.4), whereas no differences were found in the absolute hand-related CST volumes (p>0.4). CST leg-related streamline volumes, normalized to hemispheric white matter volumes, declined with age in the right hemisphere only (R=-.51; p=0.004). Absolute leg-related CST streamline volumes showed similar, but slightly weaker correlations. Hand-related absolute or normalized CST streamline volumes showed no age-related variations on either side. These results suggest differential development of CST segments controlling hand vs. leg movements. Asymmetric volume changes in the lower limb motor pathway may be secondary to gradually strengthening left hemispheric dominance and is consistent with previous data suggesting that footedness is a better predictor of hemispheric lateralization than handedness.

Low Threshold Monopolar Motor Mapping for Resection of Motor-eloquent Brain Lesions in Children and Adolescents

Aims: Resection of lesions in proximity to the primary motor cortex (M1) and the corticospinal tract (CST) is generally regarded as high-risk surgery due to reported rates of post-operative severe deficits of up to 50%. Our objective was to determine the feasibility and safety of low-threshold motor mapping and its efficacy for increasing the extent of lesion resection in the proximity of M1 and the CST in children and adolescents.

Low-threshold monopolar motor mapping for resection of lesions in motor eloquent areas in children and adolescents

Resection of lesions close to the primary motor cortex (M1) and the corticospinal tract (CST) is generally regarded as high-risk surgery due to reported rates of postoperative severe deficits of up to 50%. The authors' objective was to determine the feasibility and safety of low-threshold motor mapping and its efficacy for increasing the extent of lesion resection in the proximity of M1 and the CST in children and adolescents. The authors analyzed 8 consecutive pediatric patients in whom they performed 9 resections for lesions within or close (≤ 10 mm) to M1 and/or the CST. Monopolar high-frequency motor mapping with train-of-five stimuli (pulse duration 500 μsec, interstimulus interval 4.0 msec, frequency 250 Hz) was used. The motor threshold was defined as the minimal stimulation intensity that elicited motor evoked potentials (MEPs) from target muscles (amplitude > 30 μV). Resection was performed toward M1 and the CST at sites negative to 1- to 3-mA high-frequency train-of-five stimulation. The M1 was identified through high-frequency train-of-five via application of varying low intensities. The lowest motor thresholds after final resection ranged from 1 to 9 mA in 8 cases and up to 18 mA in 1 case, indicating proximity to motor neurons. Intraoperative electroencephalography documented an absence of seizures during all surgeries. Two transient neurological deficits were observed, but there were no permanent deficits. Postoperative imaging revealed complete resection in 8 patients and a very small remnant (< 0.175 cm3) in 1 patient. High-frequency train-of-five with a minimal threshold of 1-3 mA is a feasible and safe procedure for resections in the proximity of the CST. Thus, low-threshold motor mapping might help to expand the area for safe resection in pediatric patients with lesions located within the precentral gyrus and close to the CST, and may be regarded as a functional navigational tool. The additional use of continuous MEP monitoring serves as a safety feedback for the functional integrity of the CST, especially because the true excitability threshold in children is unknown.

Functional reorganization of the corticospinal tract in a pediatric patient with an arteriovenous malformation

Presurgical mapping in a pediatric patient diagnosed with arteriovenous malformation in the left hemisphere revealed a case of apparent functional reorganization of a white matter tract. Magnetoencephalography (MEG) was used to identify the motor fields following hand movement. As expected, motor field activity for the left hand was detected in the right hemisphere. Surprisingly, MEG activity was also detected in the right hemisphere following movement of the right hand. MEG activations served as seeds from which to launch diffusion tensor imaging tractography to delineate the corticospinal tracts (CSTs). Using the MEG activation for movement of the right hand, we delineated a tract in the right hemisphere. A tract corresponding to motor function for the left hand was also delineated in the right hemisphere. For comparison, the CSTs of the patient were launched from anatomical landmarks at the precentral gyrus, and were successfully delineated in each hemisphere. Our findings suggest that the functional delineation of white matter pathways may be more sensitive than anatomical delineation for identifying reorganization of the developing brain in response to a lesion. This study is, to our knowledge, the first description of a functional reorganization of an existing tract to serve as a CST in children.

Patterns of Structural Reorganization of the Corticospinal Tract in Children With Sturge-Weber Syndrome

BackgroundReorganization of the corticospinal tract after early damage can limit motor deficit. In this study, we explored patterns of structural corticospinal tract reorganization in children with Sturge-Weber syndrome. MethodsFive children (age 1.5-7 years) with motor deficit resulting from unilateral Sturge-Weber syndrome were studied prospectively and longitudinally (1-2 years follow-up). Corticospinal tract segments belonging to hand and leg movements were separated and their volume was measured by diffusion tensor imaging tractography using a recently validated method. Corticospinal tract segmental volumes were normalized and compared between the Sturge-Weber syndrome children and age-matched healthy controls. Volume changes during follow-up were also compared with clinical motor symptoms. ResultsIn the Sturge-Weber syndrome children, hand-related (but not leg-related) corticospinal tract volumes were consistently decreased in the affected cerebral hemisphere at baseline. At follow-up, two distinct patterns of hand corticospinal tract volume changes emerged. (1) Two children with extensive frontal lobe damage showed a corticospinal tract volume decrease in the lesional hemisphere and a concomitant increase in the nonlesional (contralateral) hemisphere. These children developed good hand grasp but no fine motor skills. (2) The three other children, with relative sparing of the frontal lobe, showed an interval increase of the normalized hand corticospinal tract volume in the affected hemisphere; these children showed no gross motor deficit at follow-up. ConclusionsDiffusion tensor imaging tractography can detect differential abnormalities in the hand corticospinal tract segment both ipsi- and contralateral to the lesion. Interval increase in the corticospinal tract hand segment suggests structural reorganization, whose pattern may determine clinical motor outcome and could guide strategies for early motor intervention.

Comparing quantitative tractography metrics of motor and sensory pathways in children with periventricular leukomalacia and different levels of gross motor function

The neural tracts responsible for gross motor dysfunction in children with spastic cerebral palsy (CP) caused by periventricular leukomalacia remain unknown. This study investigated both sensory and motor tracts using diffusion tensor tractography (DTT). Brain MRIs with diffusion tensor imaging (DTI) performed on 19 children (ten boys and nine girls) with bilateral spastic CP were analyzed. DTT was reconstructed from DTI. Participants were classified according to gross motor function measured with Gross Motor Function Classification System (GMFCS). Those with GMFCS levels I-III comprised the high-functioning group (n = 11), and those with GMFCS levels IV-V comprised the low-functioning group (n = 8). We compared DTT-based metrics, such as fractional anisotropy, apparent diffusion coefficient, and fiber number and volume, between the groups. In the corticospinal tract, the volume and number of fibers were significantly higher in the high-functioning group (p < 0.001), whereas the fractional anisotropy and apparent diffusion coefficient of the corticospinal tract did not differ significantly between the groups. In the somotosensory tract and posterior thalamic radiation, none of the DTT parameters differed significantly between the groups. Children with bilateral spastic CP with differing levels of gross motor function have corresponding differences detectable on DTT in their corticospinal tracts but not in their somatosensory tracts and posterior thalamic radiations. In addition, the number and volume of fibers, but not fractional anisotropy values or apparent diffusion coefficients, are lower in the corticospinal tracts in children with low gross motor function than in those with high gross motor function.

Diffusion Tensor MR Imaging Tractography of the Pyramidal Tracts and Corpus Callosum in Children with Right-Sided Congenital Hemiparesis

This study used diffusion tensor tractography to evaluate the diffusion parameters of the corpsus callosum and asymmetry in the diffusion parameters of the corticospinal tracts in children with congenital hemiparesis. Precision moving critically correlates with the integrity of the pyramidal tracts as evidenced in congenital hemiparesis by the correlation found between corticospinal lesions and motor deficits. Therefore we hypothesize that diffusion parameters correlate with the severity of hemiparesis measured using the Bayley Scales of Infant Development.

The corticospinal tract in Sturge–Weber syndrome: A diffusion tensor tractography study

Objective To utilize diffusion tensor tractography and evaluate the integrity of the corticospinal tract in children with unilateral Sturge–Weber syndrome (SWS). Methods: Sixteen children (age: 1.5–12.3 years) with SWS involving one hemisphere and varying degrees of motor deficit, underwent magnetic resonance imaging (MRI) as part of a prospective clinical research study. Diffusion tensor imaging (DTI) was obtained and fiber tracking of the corticospinal tract was performed yielding average FA and ADC values along the pathway. These values were compared between the two hemispheres (affected vs. unaffected) and also correlated with the degree of motor deficits, after correction for age. Results: Corticospinal tract FA values on the side of the affected hemisphere were lower ( p = 0.008) and ADC values were higher ( p = 0.011) compared to the normal side. Furthermore, FA and ADC values on the side of the angioma did not show the normal age-related variations, which the contralateral corticospinal pathway values did demonstrate. Although none of the patients had severe hemiparesis, those with moderate motor deficit had increased ADC values, as compared to those with mild ( p = 0.009) or no motor deficit ( p = 0.045). Conclusion: MRI with DTI shows abnormalities of the corticospinal tract in children with SWS even before severe motor impairment develops. Thus, DTI can be a clinically useful method to evaluate the integrity of the corticospinal tract in young children who are at risk for progressive motor dysfunction.

Ontogeny of ipsilateral corticospinal projections: a developmental study with transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) has been used to describe the maturation of the corticospinal tract in children. Ipsilateral corticospinal connections have been demonstrated with TMS in patients with congenital mirror movements, in patients after hemispherectomy, and in children with hemiplegic cerebral palsy. The goal of the study was to find out whether corticospinal ipsilateral projections in children can be demonstrated during the first decade of life as part of normal ontogeny. For this purpose, we examined 50 normal children (age range, 3-11 years) with focal TMS over the left and right hemispheres to target muscles in proximal and distal parts of the upper extremity (first dorsal interosseus, biceps brachii, and brachioradialis). To lower the stimulation threshold, we stimulated under voluntary preinnervation. In two-thirds of the children we elicited ipsilateral motor evoked potentials (MEPs). This occurred more often in proximal than in distal muscles. The latency of the ipsilateral MEPs was about 12 to 14 msec longer than the usual contralateral response. From the age of 10, and in adults, ipsilateral MEPs could not be detected. Also considering lesion data from adult patients, the most likely explanation for the disappearance of ipsilateral corticospinal connections after the age of 10 years is an increasing transcallosal inhibitory influence during development. The presence of ipsilateral corticospinal connections appears to be a normal state in ontogeny.