Long-latency motor evoked potentials in congenital hemiplegia

Ipsilateral Motor Evoked Potentials in a Preschool-age Child With Traumatic Brain Injury: A Case Report

To the best of our knowledge, the upper age limit at which post-neonatal cerebral palsy (CP) can manifest remains uncertain. This uncertainty is attributed to the lack of objective parameters for assessing the developing brain. In a previous study, we reported that an ipsilateral corticospinal projection associated with brain injury, as manifested in the paretic hand of a CP patient, had never been observed in individuals aged > 2 years. In this case report, we present an instance of ipsilateral motor evoked potential (iMEP) in a girl whose traumatic brain injury occurred at the age of 4 years. This case is the oldest in which brain injury occurred and iMEP was maintained. In conclusion, iMEP can be a valuable indicator of motor system plasticity in the developing brain.

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.

Hand function development of children with hemiplegic cerebral palsy: A scoping review

PURPOSE

Hemiplegic cerebral palsy (hCP) typically impacts sensorimotor control of the hand, but comprehensive assessments of the hands of children with hCP are relatively rare. This scoping review summarizes the development of hand function for children with hCP.

METHODS

This scoping review focused on the development of hand function in children with hCP. Electronic databases (PubMed, PEDro, Web of Science, CINAHL, and SpringerLink) were searched to identify studies assessing hand function in children with hCP. The search was performed using keywords (e.g., "hemiplegia"). An iterative approach verified by two authors was used to select the studies. Articles which reported quantitative data for children with hCP on any items of a specified set of hand evaluations were included. Measures were sorted into three categories: quantitative neuromechanics, clinical assessments, and clinical functional evaluations.

RESULTS

Initial searches returned 1536 articles, 131 of which were included in the final review. Trends between assessment scores and age were examined for both hands.

CONCLUSION

While several studies have evaluated hand function in children with hCP, the majority relied on clinical scales, assessments, or qualitative descriptions. Further assessments of kinematics, kinetics, and muscle activation patterns are needed to identify the underlying impairment mechanisms that should be targeted for treatment.

Developmental and Interventional Plasticity of Motor Maps after Perinatal Stroke

Within the perinatal stroke field, there is a need to establish preclinical models where putative biomarkers for motor function can be examined. In a mouse model of perinatal stroke, we evaluated motor map size and movement latency following optogenetic cortical stimulation against three factors of post-stroke biomarker utility: (1) correlation to chronic impairment on a behavioral test battery; (2) amenability to change using a skilled motor training paradigm; and (3) ability to distinguish individuals with potential to respond well to training. Thy1-ChR2-YFP mice received a photothrombotic stroke at postnatal day 7 and were evaluated on a battery of motor tests between days 59 and 70. Following a cranial window implant, mice underwent longitudinal optogenetic motor mapping both before and after 3 weeks of skilled forelimb training. Map size and movement latency of both hemispheres were positively correlated with impaired spontaneous forelimb use, whereas only ipsilesional hemisphere map size was correlated with performance in skilled reaching. Map size and movement latency did not show groupwise changes with training; however, mice with the smallest pretraining map sizes and worst impairments demonstrated the greatest expansion of map size in response to skilled forelimb training. Overall, motor map size showed utility as a potential biomarker for impairment and training-induced modulation in specific individuals. Future assessment of the predictive capacity of post-stroke motor representations for behavioral outcome in animal models opens the possibility of dissecting how plasticity mechanisms contribute to recovery following perinatal stroke.SIGNIFICANCE STATEMENT We investigated the utility of two cortical motor representation measures (motor map size and movement onset latency) as potential biomarkers for post-stroke motor recovery in a mouse model of perinatal stroke. Both motor map size and movement latency were associated with functional recovery after perinatal stroke, with map size showing an additional association between training responsiveness and severity of impairment. Overall, both motor map size and movement onset latency show potential as neurophysiological correlates of recovery. As such, future studies of perinatal stroke rehabilitation and neuromodulation should include these measures to help explain neurophysiological changes that might be occurring in response to treatment.

The Relationship Between Hand Function and Overlapping Motor Representations of the Hands in the Contralesional Hemisphere in Unilateral Spastic Cerebral Palsy

BACKGROUND

In many children with unilateral spastic cerebral palsy (USCP), the corticospinal tract to the affected hand atypically originates in the hemisphere ipsilateral to the affected hand. Such ipsilateral connectivity is on average a predictor of poor hand function. However, there is high variability in hand function in these children, which might be explained by the complexity of motor representations of both hands in the contralesional hemisphere.

OBJECTIVE

To measure the link between hand function and the size and excitability of motor representations of both hands, and their overlap, in the contralesional hemisphere of children with USCP.

METHODS

We used single-pulse transcranial magnetic stimulation to measure the size and excitability of motor representations of both hands, and their overlap, in the contralesional hemisphere of 50 children with USCP. We correlated these measures with manual dexterity of the affected hand, bimanual performance, and mirror movement strength.

RESULTS

The main and novel findings were (1) the large overlap in contralesional motor representations of the 2 hands and (2) the moderate positive associations of the size and excitability of such shared-site representations with hand function. Such functional associations were not present for overall size and excitability of representations of the affected hand.

CONCLUSIONS

Greater relative overlap of the affected hand representation with the less-affected hand representation within the contralesional hemisphere was associated with better hand function. This association suggests that overlapping representations might be adaptively "yoked," such that cortical control of the child's less-affected hand supports that of the affected hand.

Children with cerebral palsy have altered oscillatory activity in the motor and visual cortices during a knee motor task

The neuroimaging literature on cerebral palsy (CP) has predominantly focused on identifying structural aberrations within the white matter (e.g., fiber track integrity), with very few studies examining neural activity within the key networks that serve the production of motor actions. The current investigation used high-density magnetoencephalography to begin to fill this knowledge gap by quantifying the temporal dynamics of the alpha and beta cortical oscillations in children with CP (age = 15.5 ± 3 years; GMFCS levels II–III) and typically developing (TD) children (age = 14.1 ± 3 years) during a goal-directed isometric target-matching task using the knee joint. Advanced beamforming methods were used to image the cortical oscillations during the movement planning and execution stages. Compared with the TD children, our results showed that the children with CP had stronger alpha and beta event-related desynchronization (ERD) within the primary motor cortices, premotor area, inferior parietal lobule, and inferior frontal gyrus during the motor planning stage. Differences in beta ERD amplitude extended through the motor execution stage within the supplementary motor area and premotor cortices, and a stronger alpha ERD was detected in the anterior cingulate. Interestingly, our results also indicated that alpha and beta oscillations were weaker in the children with CP within the occipital cortices and visual MT area during movement execution. These altered alpha and beta oscillations were accompanied by slower reaction times and substantial target matching errors in the children with CP. We also identified that the strength of the alpha and beta ERDs during the motor planning and execution stages were correlated with the motor performance. Lastly, our regression analyses suggested that the beta ERD within visual areas during motor execution primarily predicted the amount of motor errors. Overall, these data suggest that uncharacteristic alpha and beta oscillations within visuomotor cortical networks play a prominent role in the atypical motor actions exhibited by children with CP.

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Children with CP performed an isometric task with the knee joint.

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Children with CP had stronger alpha and beta ERD during motor planning.

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These ERD differences extended through the motor execution period.

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Occipital cortices and visual MT area alpha and beta ERD were weaker.

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Altered alpha and beta ERD were accompanied by impaired motor actions.

Mirror movements in unilateral spastic cerebral palsy: Specific negative impact on bimanual activities of daily living

AIM

Mirror movements are involuntary movements of the other hand during voluntary unimanual movements. Some, but not all children with unilateral spastic cerebral palsy (USCP) show this phenomenon. In this observational study, we investigated whether these mirror movements have a specific negative impact on bimanual activities of daily living.

METHODS

Eighteen children (six girls; age range, 6-16 years; mean age, 12 years 1 month; SD, 3 years 3 month) with USCP, nine with and nine without mirror movements, underwent the Jebsen Taylor Hand Function Test (unimanual capacity) and the Assisting Hand Assessment (bimanual performance). In addition, we measured the time the participants needed for the completion of five activities we had identified as particularly difficult for children with mirror movements.

RESULTS

Multivariate analysis demonstrated that mirror movements indeed have a specific negative impact on bimanual performance (Assisting Hand Assessment) and on the time needed for the completion of these five particularly difficult activities. This effect was independent from unimanual capacity.

CONCLUSION

Functional therapies in children with USCP and mirror movements should address this phenomenon.

Is outcome of constraint-induced movement therapy in unilateral cerebral palsy dependent on corticomotor projection pattern and brain lesion characteristics?

AIM

The aim of the study was to explore individual variations in outcome of hand function after constraint-induced movement therapy (CIMT) in relation to the organization of corticomotor projection and brain lesion characteristics in participants with unilateral cerebral palsy (CP).

METHOD

Sixteen participants (eight males, eight females; mean age 13 y, [SD 2 y] range 10-16 y) with unilateral CP (nine right-sided; Manual Ability Classification System [MACS] level I, n=1; level II, n=15) who participated in a 2-week CIMT day camp (63 h) were included in the study. Various aspects of hand function were measured by the Jebsen-Taylor Hand Function Test (JTHFT), the Assisting Hand Assessment (AHA), and the Melbourne Assessment, both before and after the day camp. Transcranial magnetic stimulation was used to explore the corticomotor organization, and brain lesion characteristics were described by visual assessment of conventional structural magnetic resonance images.

RESULTS

At a group level, the training was associated with significant improvements in JTHFT (p=0.003) and AHA (p=0.046), but not in Melbourne Assessment scores. Improvements were found in all types of corticomotor projection patterns, i.e. contralateral, mixed, and ipsilateral. There was no relationship between functional improvement and brain lesion characteristics.

INTERPRETATION

Individuals with CP experience improved motor outcomes after CIMT, independent of corticomotor projection pattern and lesion characteristics.

Aberrant synchrony in the somatosensory cortices predicts motor performance errors in children with cerebral palsy

Cerebral palsy (CP) results from a perinatal brain injury that often results in sensory impairments and greater errors in motor performance. Although these impairments have been well catalogued, the relationship between sensory processing networks and errors in motor performance has not been well explored. Children with CP and typically developing age-matched controls participated in this investigation. We used high-density magnetoencephalography to measure event-related oscillatory changes in the somatosensory cortices following tactile stimulation to the bottom of the foot. In addition, we quantified the amount of variability or errors in the isometric ankle joint torques as these children attempted to match a target. Our results showed that neural populations in the somatosensory cortices of children with CP were desynchronized by the tactile stimulus, whereas those of typically developing children were clearly synchronized. Such desynchronization suggests that children with CP were unable to fully integrate the external stimulus into ongoing sensorimotor computations. Our results also indicated that children with CP had a greater amount of errors in their motor output when they attempted to match the target force, and this amount of error was negatively correlated with the degree of synchronization present in the somatosensory cortices. These results are the first to show that the motor performance errors of children with CP are linked with neural synchronization within the somatosensory cortices.

Effects of conditioning peripheral repetitive magnetic stimulation in patients with complex regional pain syndrome

OBJECTIVES

We tested whether repetitive magnetic stimulation (rMS) induces an afferent input to the spinocerebral tract in patients with complex regional pain syndrome (CRPS).

METHODS

Cortical and spinal motor evoked potentials (cMEP and sMEP), as well as the contra- and ipsilateral silent period (cCSP and iCSP), were recorded in patients with CRPS type I before and after conditioning rMS, applied at cervical nerve roots innervating affected muscles. Patients were compared with a group of healthy subjects.

RESULTS

In the group of patients we found that cMEP amplitudes were always significantly smaller for both hemispheres. In the group of healthy subjects we found a significant prolongation of the cCSP and iCSP after rMS. This was absent in patients. SMEP were always unchanged in both groups.

DISCUSSION

This led us to the explanation that the afferent input to the motor cortical system in CRPS patients is less effective than in healthy subjects.

Cortical reorganisation in a preterm born child with unilateral watershed infarction

In this case report we describe the presence of a unilateral watershed infarction in a preterm born infant. Structural imaging in the neonatal period and in adolescence confirmed a typical lesion pattern compatible with watershed infarction in term born infants. Though the resulting parasagittal cleft transected the primary motor cortex, motor function of the affected hand was relatively spared. Functional MRI and transcranial magnetic stimulation revealed an important role for the unaffected hemisphere in motor control of the affected hand, showing once again that early cortical reorganization may lead to a near normal hand function.

Reorganization of cortical hand representation in congenital hemiplegia

When damaged perinatally, as in congenital hemiplegia (CH), the corticospinal tract usually undergoes an extensive reorganization, such as the stabilization of normally transient projections to the ipsilateral spinal cord. Whether the reorganization of the corticospinal projections occurring in CH patients is also accompanied by a topographical rearrangement of the hand representations in the primary motor cortex (M1) remains unclear. To address this issue, we mapped, for both hands, the representation of the first dorsal interosseous muscle (1DI) in 12 CH patients by using transcranial magnetic stimulation co-registered onto individual three-dimensional magnetic resonance imaging; these maps were compared with those gathered in age-matched controls (n = 11). In the damaged hemisphere of CH patients, the representation of the paretic 1DI was either found in the hand knob of M1 (n = 5), shifted caudally (n = 5), or missing (n = 2). In the intact hemisphere of six CH patients, an additional, ipsilateral, representation of the paretic 1DI was found in the hand knob, where it overlapped exactly the representation of the non-paretic 1DI. In the other six CH patients, the ipsilateral representation of the paretic 1DI was either shifted caudally (n = 2) or was lacking (n = 4). Surprisingly, in these two subgroups of patients, the representation of the contralateral non-paretic 1DI was found in a more medio-dorsal position than in controls. The present study demonstrates that, besides the well-known reorganization of the corticospinal projections, early brain injuries may also lead to a topographical rearrangement of the representations of both the paretic and non-paretic hands in M1.

Is hemiplegic cerebral palsy equivalent to amblyopia of the corticospinal system?

OBJECTIVE

Subjects with severe hemiplegic cerebral palsy have increased ipsilateral corticospinal projections from their noninfarcted cortex. We investigated whether their severe impairment might, in part, be caused by activity-dependent, competitive displacement of surviving contralateral corticospinal projections from the affected cortex by more active ipsilateral corticospinal projections from the nonaffected cortex, thereby compounding the impairment.

METHODS

Transcranial magnetic stimulation (TMS) characterized corticospinal tract development from each hemisphere over the first 2 years in 32 healthy children, 14 children with unilateral stroke, and 25 with bilateral lesions. Magnetic resonance imaging and anatomic studies compared corticospinal tract growth in 13 patients with perinatal stroke with 46 healthy subjects.

RESULTS

Infants with unilateral lesions initially had responses after TMS of the affected cortex, which became progressively more abnormal, and seven were eventually lost. There was associated hypertrophy of the ipsilateral corticospinal axons projecting from the noninfarcted cortex. Magnetic resonance imaging and anatomic studies demonstrated hypertrophy of the corticospinal tract from the noninfarcted hemisphere. TMS findings soon after the stroke did not predict impairment; subsequent loss of responses and hypertrophy of ipsilateral corticospinal axons from the noninfarcted cortex predicted severe impairment at 2 years. Infants with bilateral lesions maintained responses to TMS from both hemispheres with a normal pattern of development.

INTERPRETATION

Rather than representing "reparative plasticity," increased ipsilateral projections from the noninfarcted cortex compound disability by competitively displacing surviving contralateral corticospinal projections from the infarcted cortex. This may provide a pathophysiological explanation for why signs of hemiplegic cerebral palsy appear late and progress over the first 2 years of life.

Responses to lumbar magnetic stimulation in newborns with spina bifida

Searching for a tool to quantify motor impairment in spina bifida, transcranial and lumbar magnetic stimulation were applied in affected newborn infants. Lumbar magnetic stimulation resulted in motor evoked potentials in both the quadriceps muscle and the tibialis anterior muscle in most (11/13) subjects. However, transcranial magnetic stimulation did not lead to any response at all. A strong left-to-right correlation existed for amplitude and for latency. Lumbar magnetic stimulation proved to be applicable in newborn infants with spina bifida. Although current concepts regarding spina bifida suppose lower motor neuron dysfunction, the results of this study suggest that lower motor neuron integrity is at least partly preserved after birth. Transcranial magnetic stimulation does not lead to responses in healthy newborn infants because of insufficient synaptogenesis, myelinogenesis, and axon thickness. Therefore, conclusions on upper motor neuron function in spina bifida cannot be drawn. To what extent the method used here can achieve the aim of quantifying motor impairment is a matter of further study.

Reorganization in congenital hemiparesis acquired at different gestational ages

It is well established that the reorganizational potential of the developing human brain is superior to that of the adult brain, but whether age-dependent differences exist already in the prenatal and perinatal period is not known. We have studied sensorimotor reorganization in 34 patients with congenital hemiparesis (age range, 5-27 years), using transcranial magnetic stimulation and functional magnetic resonance imaging during simple hand movements. Underlying pathologies were brain malformations (first and second trimester lesions; n = 10), periventricular brain lesions (early third trimester lesions; n = 12), and middle cerebral artery infarctions (late third trimester lesions; n = 12). Of this cohort, eight patients with malformations and all patients with periventricular lesions have been published previously. In all three groups of pathologies, transcranial magnetic stimulation identified patients in whom the paretic hand was controlled via ipsilateral corticospinal projections from the contralesional hemisphere (n = 16). In these patients, the motor dysfunction of the paretic hand correlated significantly with the timing period of the underlying brain lesion. This demonstrates that the efficacy of reorganization with ipsilateral corticospinal tracts indeed decreases during pregnancy.