Influence of the corticospinal tract wiring pattern on sensorimotor functional connectivity and clinical correlates of upper limb function in unilateral cerebral palsy

Reduced corticospinal drive to antagonist muscles of upper and lower limbs during hands-and-knees crawling in infants with cerebral palsy: Evidence from intermuscular EMG-EMG coherence

BACKGROUND

There is growing interest in understanding the central control of hands-and-knees crawling, especially as a significant motor developmental milestone for early assessment of motor dysfunction in infants with cerebral palsy (CP) who have not yet acquired walking ability. In particular, CP is known to be associated with walking dysfunctions caused by early damage and incomplete maturation of the corticospinal tract. However, the extent of damage to the corticospinal connections during crawling in infants with CP has not been fully clarified. Therefore, this study aimed to investigate the disparities in intermuscular EMG-EMG coherence, which serve as indicators of corticospinal drives to antagonist muscles in the upper and lower limbs during crawling, between infants with and without CP.

METHODS

This study involved 15 infants diagnosed with CP and 20 typically developing (TD) infants. Surface EMG recordings were obtained from two pairs of antagonist muscles in the upper limbs (triceps brachii (TB) and biceps brachii (BB)) and lower limbs (quadriceps femoris (QF) and hamstrings (HS)), while the infants performed hands-and-knees crawling at their self-selected velocity. Intermuscular EMG-EMG coherence was computed in two frequency bands, the beta band (15-30 Hz) and gamma band (30-60 Hz), which indicate corticospinal drive. Additionally, spatiotemporal parameters, including crawling velocity, cadence, duration, and the percentage of stance phase time, were calculated for comparison. Spearman rank correlations were conducted to assess the relationship between EMG-EMG coherence and crawling spatiotemporal parameters.

RESULTS

Infants with CP exhibited significantly reduced crawling velocity, decreased cadence, longer cycle duration, and a higher percentage of stance phase time compared to TD infants. Furthermore, CP infants demonstrated decreased coherence in the beta and gamma frequency bands (indicators of corticospinal drive) in both upper and lower limb muscles. Regarding limb-related differences in the beta and gamma coherence, significant disparities were found between upper and lower limb muscles in TD infants (p < 0.05), but not in infants with CP (p > 0.05). Additionally, significant correlations between coherence metrics and crawling spatiotemporal parameters were identified in the TD group (p < 0.05), while such correlations were not evident in the CP group.

CONCLUSIONS

Our findings suggest that the corticospinal drive may functionally influence the central control of antagonist muscles in the limbs during typical infant crawling. This functional role could be impaired by neurological conditions such as cerebral palsy. The neurophysiological markers of corticospinal drive, specifically intermuscular EMG-EMG coherence during crawling in infants with cerebral palsy, could potentially serve as a tool to assess developmental response to therapy.

Functional connectivity of sensorimotor network is enhanced in spastic diplegic cerebral palsy: A multimodal study using fMRI and MEG

OBJECTIVE

To assess the effects to functional connectivity (FC) caused by lesions related to spastic diplegic cerebral palsy (CP) in children and adolescents using multiple imaging modalities.

METHODS

We used resting state magnetoencephalography (MEG) envelope signals in alpha, beta and gamma ranges and resting state functional magnetic resonance imaging (fMRI) signals to quantify FC between selected sensorimotor regions of interest (ROIs) in 11 adolescents with spastic diplegic cerebral palsy and 24 typically developing controls. Motor performance of the hands was quantified with gross motor, fine motor and kinesthesia tests.

RESULTS

In fMRI, participants with CP showed enhanced FC within posterior parietal regions; in MEG, they showed enhanced interhemispheric FC between sensorimotor regions and posterior parietal regions both in alpha and lower beta bands. There was a correlation between the kinesthesia score and fronto-parietal connectivity in the control population.

CONCLUSIONS

CP is associated with enhanced FC in sensorimotor network. This difference is not correlated with hand coordination performance. The effect of the lesion is likely not fully captured by temporal correlation of ROI signals.

SIGNIFICANCE

Brain lesions can show as increased temporal correlation of activity between remote brain areas. We suggest this effect is likely separate from typical physiological correlates of functional connectivity.

Assessing structural integrity of the pyramidal tracts with diffusion spectrum imaging to predict postoperative motor function in pediatric epilepsy patients with hemispherectomy

Background

Hemispherectomy is an effective treatment option for patients with drug-resistant epilepsy caused by hemispheric lesions. However, patients often have deterioration of their motor functions postoperatively. Diffusion spectrum imaging (DSI) was reliable in presenting the natural shape of the white matter fibers. At the same time, the natural sprawl pyramid tract (PT) might be more intuitive for predicting postoperative motor functions. Therefore, we assessed the motor functions by the natural shape revealed by DSI tractography.

Methods

Ten children with drug-resistant epilepsy who were candidates for hemispherectomy performed DSI PTs tractography and transcranial magnetic stimulation (TMS) for motor mapping. The motor function was evaluated with muscle strength and hand grasping capability. Pyramidal tract (PT) structural integrity and TMS mapping results were compared between patients who remained stable and those with deteriorated motor functions. Receiver operating characteristic (ROC) curves with PTs asymmetric ratio were analyzed to evaluate DSI tractography diagnostic value.

Results

All patients underwent DSI acquisition, while four patients successfully performed TMS. One patient had no response to TMS until the maximal machine output was reached. Four patients failed to perform TMS due to lacking cooperation. One patient was contraindicated to TMS. DSI successfully reconstructed the sharp angle fan-shaped PTs within the hemisphere. The accurate fiber distribution with fiber termination and thickness within the lesioned hemisphere was replicated with DSI tractography. No significance was found in patients’ age, sex, seizure frequency, or medication between patients with stable or deteriorated postoperative motor functions. DSI effectively predicted postoperative motor function as stable with damaged PTs, mild deterioration with atrophied PTs, and intact PTs with contralateral innervation confirmed by intracranial stimulation. The area under the curve (AUC) of DSI tractography was 0.84. According to ROC, the cut-off value of PTs asymmetric ratio was 11.5% with 100% sensitivity and 75% specificity. The sensitivity and specificity of TMS were 2/3 and 1/2, respectively.

Conclusions

The anatomic integrity of PTs with DSI tractography could effectively predict postoperative motor function after hemispherectomy. This enables neurosurgeons to inform patients and relatives about postoperative motor functions with direct morphological evidence of PTs to help them with their surgical decisions.

The impact of brain lesion characteristics and the corticospinal tract wiring on mirror movements in unilateral cerebral palsy

Mirror movements (MM) influence bimanual performance in children with unilateral cerebral palsy (uCP). Whilst MM are related to brain lesion characteristics and the corticospinal tract (CST) wiring pattern, the combined impact of these neurological factors remains unknown. Forty-nine children with uCP (mean age 10y6mo) performed a repetitive squeezing task to quantify similarity (MM-similarity) and strength (MM-intensity) of the MM activity. We used MRI data to evaluate lesion type (periventricular white matter, N = 30; cortico-subcortical, N = 19), extent of ipsilesional damage, presence of bilateral lesions, and damage to basal ganglia, thalamus and corpus callosum. The CST wiring was assessed with Transcranial Magnetic Stimulation (17 CSTcontralateral, 16 CSTipsilateral, 16 CSTbilateral). Data was analyzed with regression analyses. In the more-affected hand, MM-similarity and intensity were higher with CSTbilateral/ipsilateral. In the less-affected hand, MM-similarity was higher in children with (1) CSTcontra with CSC lesions, (2) CSTbilat/ipsi with PVL lesions and (3) CSTbilat/ipsi with unilateralized lesions. MM-intensity was higher with larger damage to the corpus callosum and unilateral lesions. A complex combination of neurological factors influences MM characteristics, and the mechanisms differ between hands.

Robotic mapping of motor cortex in children with perinatal stroke and hemiparesis

Brain stimulation combined with intensive therapy may improve hand function in children with perinatal stroke‐induced unilateral cerebral palsy (UCP). However, response to therapy varies and underlying neuroplasticity mechanisms remain unclear. Here, we aimed to characterize robotic motor mapping outcomes in children with UCP. Twenty‐nine children with perinatal stroke and UCP (median age 11 ± 2 years) were compared to 24 typically developing controls (TDC). Robotic, neuronavigated transcranial magnetic stimulation was employed to define bilateral motor maps including area, volume, and peak motor evoked potential (MEP). Map outcomes were compared to the primary clinical outcome of the Jebsen–Taylor Test of Hand Function (JTT). Maps were reliably obtained in the contralesional motor cortex (24/29) but challenging in the lesioned hemisphere (5/29). Within the contralesional M1 of participants with UCP, area and peak MEP amplitude of the unaffected map were larger than the affected map. When comparing bilateral maps within the contralesional M1 in children with UCP to that of TDC, only peak MEP amplitudes were different, being smaller for the affected hand as compared to TDC. We observed correlations between the unaffected map when stimulating the contralesional M1 and function of the unaffected hand. Robotic motor mapping can characterize motor cortex neurophysiology in children with perinatal stroke. Map area and peak MEP amplitude may represent discrete biomarkers of developmental plasticity in the contralesional M1. Correlations between map metrics and hand function suggest clinical relevance and utility in studies of interventional plasticity.

Participation after childhood stroke: Is there a relationship with lesion size, motor function and manual ability?

BACKGROUND

Childhood arterial ischemic stroke (AIS) is associated with significant morbidity with up to 50% of affected children developing hemiparesis. Hemiparesis is assumed to influence participation within the peer group, but it is unclear to what extent its severity affects participation in different areas of social life.

METHODS

Thirteen children (mean age 9y6m) with AIS (6 without hemiparesis, 7 with hemiparesis) and 21 controls (mean age 9y8m) participated. We scored hemiparesis severity with hand strength asymmetry (pinch and grip strength), measured with a dynamometer. We assessed manual ability (ABILHAND-Kids), socioeconomic status (Family Affluence Scale) and participation (Participation and Environment Measure - Children and Youth). From structural MRI, we measured lesion size. We investigated differences in participation and its relationship with hemiparesis severity using non-parametric partial correlations (controlling for lesion size, manual ability, and socioeconomic status), interpreted as absent (r < 0.25), weak (r = 0.25-0.50), moderate (r = 0.50-0.75) or strong (r > 0.75). Analyses were performed in jamovi 1.6.3.

RESULTS

Children with AIS (with or without hemiparesis) showed reduced participation frequency at school (p < 0.001), whilst participation at home and in the community resembled that of their peers. Severity of hemiparesis was moderately related to frequency and involvement at home and to involvement and desire for change in the community, although unrelated to school participation.

CONCLUSION

Reduced participation in school life requires close attention in the follow-up of children with AIS - regardless of the severity of hemiparesis. Participation at home and in the community is related to hemiparesis severity and may be improved with participation-focused motor intervention strategies.

Brain functional reorganization in children with hemiplegic cerebral palsy: Assessment with TMS and therapeutic perspectives

Transcranial magnetic stimulation (TMS) can be a useful tool for the assessment of the brain functional reorganization in subjects with hemiplegic cerebral palsy (HCP). In this review, we performed a systematic search of all studies using TMS in order to explore the neuroplastic changes that occur in HCP patients. We aimed at investigating the usefulness of TMS to explore cortical excitability, plasticity and connectivity changes in HCP. Children with HCP due to unilateral lesions of the corticospinal system had ipsilateral motor evoked potentials (MEPs) similar to those recorded contralaterally. TMS studies demonstrated that occupational and constraint-induced movement therapy were associated with significant improvements in contralateral and ipsilateral corticomotor projection patterns. In addition, after intensive bimanual therapy, children with HCP showed increased activation and size of the motor areas controlling the affected hand. A TMS mapping study revealed a mediolateral location of the upper and lower extremity map motor cortical representations. Deficits in intracortical and interhemispheric inhibitory mechanisms were observed in HCP. Early hand function impairment correlated with the extension of brain damage, number of involved areas, and radiological signs of corticospinal tract (CST) degeneration. Clinical mirror movements (MMs) correlated with disability and CST organization in subjects with HCP and a positive relationship was found between MMs and MEPs strength. Therefore, TMS studies have shed light on important pathophysiological aspects of motor cortex and CST reorganization in HCP patients. Furthermore, repetitive TMS (rTMS) might have therapeutic effects on CST activities, functional connectivity and clinical status in children with HCP.

Motor Organization in Schizencephaly: Outcomes of Transcranial Magnetic Stimulation and Diffusion Tensor Imaging of Motor Tract Projections Correlate with the Different Domains of Hand Function

Objective

Schizencephaly is a rare congenital malformation that causes motor impairment. To determine the treatment strategy, each domain of the motor functions should be appropriately evaluated. We correlated a color map of diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS) with the hand function test (HFT) to identify the type of hand function that each test (DTI and TMS) reflects. Further, we attempted to demonstrate the motor neuron organization in schizencephaly.

Method

This retrospective study was conducted on 12 patients with schizencephaly. TMS was conducted in the first dorsal interosseous (FDI), biceps (BB), and deltoid muscles of the upper extremity, and contralateral MEP (cMEP) and ipsilateral MEP (iMEP) were recorded. The HFT included the grip strength, box and block (B&B), and 9-hole peg test. The schizencephalic cleft was confirmed using magnetic resonance imaging, and the corticospinal tract (CST) was identified using the color map of DTI. The symmetry indices for the peduncle and CST at pons level were calculated as the ratios of the cross-sectional area of the less-affected side and that of the more-affected side.

Result

In the more-affected hemisphere TMS, no iMEP was obtained. In the less-affected hemisphere TMS, the iMEP response was detected in 9 patients and cMEP in all patients, which was similar to the pattern observed in unilateral lesion. Paretic hand grip strength was strongly correlated with the presence of iMEP (p = 0.044). The symmetry index of the color map of DTI was significantly correlated with the B&B (p = 0.008, R ² = 0.416), whereas the symmetry index of the peduncle was not correlated with all HFTs.

Conclusion

In patients with schizencephaly, the iMEP response rate is correlated with the hand function related to strength, while the symmetricity of the CST by the color map of DTI is correlated with the hand function associated with dexterity. Additionally, we suggest the possible motor organization pattern of schizencephaly following interhemispheric competition.

Relationship between resting-state fMRI functional connectivity with motor and language outcome after perinatal brain injury - A systematic review

Perinatal brain injury is a significant cause of adverse neurodevelopmental outcomes. The objective of this systematic review was to identify patterns of altered brain function, quantified using functional connectivity (FC) changes in resting-state fMRI (rs-fMRI) data, that were associated with motor and language outcomes in individuals with a history of perinatal brain injury. A systematic search using electronic databases was conducted to identify relevant studies. A total of 10 studies were included in the systematic review, representing 260 individuals with a history of perinatal brain injury. Motor and language outcomes were measured at time points ranging from 4 months to 29 years 1 month. Relations between FC and motor measures revealed increased intra-hemispheric FC, reduced inter-hemispheric FC and impaired lateralization of motor-related brain regions associated with motor outcomes. Altered FC within sensorimotor, visual, cerebellum and frontoparietal networks, and between sensorimotor, visual, auditory and higher-order networks, including cerebellum, frontoparietal, default-mode, salience, self-referential and attentional networks were also associated with motor outcomes. In studies assessing the relationship between rs-fMRI and language outcome, reduced intra-hemispheric FC, increased inter-hemispheric FC and right-hemisphere lateralization of language-related brain regions correlated with language outcomes. Evidence from this systematic review suggests a possible association between diaschisis and motor and language impairments in individuals after perinatal brain lesions. These findings support the need to explore the contributions of additional brain regions functionally connected but remote from the primary lesioned brain area for targeted treatments and appropriate intervention, though more studies with increased standardization across neuroimaging and neurodevelopmental assessments are needed.

Improvements in Upper Extremity Function Following Intensive Training Are Independent of Corticospinal Tract Organization in Children With Unilateral Spastic Cerebral Palsy: A Clinical Randomized Trial

Background/Objectives: Intensive training of the more affected upper extremity (UE) has been shown to be effective for children with unilateral spastic cerebral palsy (USCP). Two types of UE training have been particularly successful: Constraint-Induced Movement Therapy (CIMT) and Bimanual training. Reorganization of the corticospinal tract (CST) early during development often occurs in USCP. Prior studies have suggested that children with an ipsilateral CST controlling the affected UE may improve less following CIMT than children with a contralateral CST. We tested the hypothesis that improvements in UE function after intensive training depend on CST laterality.

Study Participants and Setting: Eighty-two children with USCP, age 5 years 10 months to 17 years, University laboratory setting.

Materials/Methods: Single-pulse transcranial magnetic stimulation (TMS) was used to determine each child's CST connectivity pattern. Children were stratified by age, sex, baseline hand function and CST connectivity pattern, and randomized to receive either CIMT or Bimanual training, each of which were provided in a day-camp setting (90 h). Hand function was tested before, immediately and 6 months after the intervention with the Jebsen-Taylor Test of Hand Function, the Assisting Hand Assessment, the Box and Block Test, and ABILHAND-Kids. The Canadian Occupational Performance Measure was used to track goal achievement and the Pediatric Evaluation of Disability Inventory was used to assess functioning in daily living activities at home.

Results: In contrast to our hypothesis, participants had statistically similar improvements for both CIMT and Bimanual training for all measures independent of their CST connectivity pattern (contralateral, ipsilateral, or bilateral) (p < 0.05 in all cases).

Conclusions/Significance: The efficacy of CIMT and Bimanual training is independent of CST connectivity pattern. Children with an ipsilateral CST, previously thought to be maladaptive, have the capacity to improve as well as children with a contralateral or bilateral CST following intensive CIMT or Bimanual training.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT02918890.

Functional connectivity and upper limb function in patients after pediatric arterial ischemic stroke with contralateral corticospinal tract wiring

To develop individualized motor rehabilitation, knowledge of the relationship between neuroplastic reorganization and motor recovery after pediatric arterial ischemic stroke (AIS) is crucial. Thus, we investigated functional connectivity in patients after AIS with good motor outcome and in patients with hemiparesis compared with typically developing peers. We included 18 patients (n = 9 with hemiparesis, n = 9 with good motor outcome) with pediatric AIS in the chronic phase (≥ 2 years after diagnosis, diagnosed > 16 years) and 18 peers matched by age and gender. Participants underwent a standardized motor assessment, single-pulse transcranial magnetic stimulation to determine the type of corticospinal tract wiring, and resting-state functional magnetic resonance imaging to examine motor network connectivity. Corticospinal tract wiring was contralateral in all participants. Patients with hemiparesis had lower interhemispheric connectivity strength compared with patients with good clinical outcome and peers. Patients with good clinical outcome had higher intrahemispheric connectivity strength compared with peers. Further, higher intrahemispheric connectivity was related to better motor outcome in patients. Our findings suggest that better motor outcome after pediatric AIS is related to higher motor network connectivity strength. Thus, resting-state functional connectivity might be predictive for motor recovery after pediatric AIS.

Mu Rhythm during Standing and Walking Is Altered in Children with Unilateral Cerebral Palsy Compared to Children with Typical Development

Background: Rehabilitation in cerebral palsy (CP) seeks to harness neuroplasticity to improve movement, including walking, yet cortical activation underlying gait is not well understood. Methods: We used electroencephalography (EEG) to compare motor related cortical activity, measured by mu rhythm, during quiet standing and treadmill walking in 10 children with unilateral CP and 10 age- and sex-matched children with typical development (TD). Peak mu band frequency, mu rhythm desynchronization (MRD), and gait related intra- and inter-hemispheric coherence were examined. Results: MRD during walking was observed bilaterally over motor cortex in both cohorts but peak mu band frequency showing MRD was significantly lower in CP compared to TD. Coherence during quiet standing between motor and frontal regions was significantly higher in the non-dominant compared to dominant hemisphere in CP with no hemispheric differences in TD. Conclusions: EEG-based measures should be further investigated as clinical biomarkers for atypical motor development and to assess rehabilitation effectiveness.

Imaging Developmental and Interventional Plasticity Following Perinatal Stroke

Perinatal stroke occurs around the time of birth and leads to lifelong neurological disabilities including hemiparetic cerebral palsy. Magnetic resonance imaging (MRI) has revolutionized our understanding of developmental neuroplasticity following early injury, quantifying volumetric, structural, functional, and metabolic compensatory changes after perinatal stroke. Such techniques can also be used to investigate how the brain responds to treatment (interventional neuroplasticity). Here, we review the current state of knowledge of how established and emerging neuroimaging modalities are informing neuroplasticity models in children with perinatal stroke. Specifically, we review structural imaging characterizing lesion characteristics and volumetrics, diffusion tensor imaging investigating white matter tracts and networks, task-based functional MRI for localizing function, resting state functional imaging for characterizing functional connectomes, and spectroscopy examining neurometabolic changes. Key challenges and exciting avenues for future investigations are also considered.

Understanding the impact of bilateral brain injury in children with unilateral cerebral palsy

The presence of bilateral brain injury in patients with unilateral cerebral palsy (CP) may impact neuroplasticity in the ipsilateral hemisphere; however, this pattern of injury is typically under‐analyzed due to the lack of methods robust to severe injury. In this study, injury‐robust methods have been applied to structural brain magnetic resonance imaging (MRI) data of a cohort of 91 children with unilateral CP (37 with unilateral and 54 with bilateral brain injury, 4–17 years) and 44 typically developing controls (5–17 years), to determine how brain structure is associated with concurrent motor function, and if these associations differ between patients with unilateral or bilateral injury. Regression models were used to associate these measures with two clinical scores of hand function, with patient age, gender, brain injury laterality, and interaction effects included. Significant associations with brain structure and motor function were observed (Pearson's r = .494–.716), implicating several regions of the motor pathway, and demonstrating an accurate prediction of hand function from MRI, regardless of the extent of brain injury. Reduced brain volumes were observed in patients with bilateral injury, including volumes of the thalamus and corpus callosum splenium, compared to those with unilateral injury, and the healthy controls. Increases in cortical thickness in several cortical regions were observed in cohorts with unilateral and bilateral injury compared to controls, potentially suggesting neuroplasticity might be occurring in the inferior frontal gyrus and the precuneus. These findings identify prospective useful target regions for transcranial magnetic stimulation intervention.

The relationship between neuroimaging and motor outcome in children with cerebral palsy: A systematic review-Part B diffusion imaging and tractography

BACKGROUND

Diffusion magnetic resonance imaging (dMRI) is able to detect, localize and quantify subtle brain white matter abnormalities that may not be visible on conventional structural MRI. Over the past years, a growing number of studies have applied dMRI to investigate structure-function relationships in children with cerebral palsy (CP).

AIMS

To provide an overview of the recent literature on dMRI and motor function in children with CP.

METHODS

A systematic literature search was conducted in PubMed, Embase, Cochrane Central Register of Controlled trials, Cinahl and Web of Science from 2012 onwards.

RESULTS

In total, 577 children with CP in 19 studies were included. Sixteen studies only included unilateral CP, while none included dyskinetic CP. Most studies focused on specific regions/tracts of interest (n = 17) versus two studies that investigated the whole brain. In unilateral and bilateral CP, white matter abnormalities were widespread including non-motor areas. In unilateral CP, consistent relationships were found between white matter integrity of the corticospinal tract and somatosensory pathways (e.g. thalamocortical projections, medial lemniscus) with upper limb sensorimotor function. The role of commissural and associative tracts remains poorly investigated. Also results describing structure-function relationships in bilateral CP are scarce (n = 3).

CONCLUSIONS

This review underlines the importance of both the motor and somatosensory tracts for upper limb sensorimotor function in unilateral CP. However, the exact contribution of each tract requires further exploration. In addition, research on the relevance of non-motor pathways is warranted, as well as studies including other types of CP.