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.

The effects of modified constraint-induced movement therapy combined with intensive bimanual training in children with brachial plexus birth injury: a retrospective data base study.

BACKGROUND: In children with Brachial Plexus Birth Injury, a non-use of the affected upper limb despite sufficient capacity, is sometimes observed, called developmental disregard. The combination of modified constraint-induced-movement-therapy with bimanual training is frequently applied to overcome developmental disregard in unilateral Cerebral Palsy. In the current study the effects of the combination of modified constraint-induced-movement-therapy with bimanual training are investigated in children with Brachial Plexus Birth Injury in comparison to children with unilateral Cerebral Palsy. We hypothesize that the combination of modified constraint-induced-movement-therapy with bimanual training is effective in Brachial Plexus Birth Injury. METHODS: Data of 19 children with Brachial Plexus Birth Injury (Mage: 4.1 years) and 18 with unilateral Cerebral Palsy (Mage: 4.5 years) were compared. The effects of modified constraint-induced-movement-therapy with bimanual training (54 h modified constraint-induced-movement-therapy, 18 h bimanual training, 8-10 weeks) was investigated by assessing spontaneous affected-upper-limb-use ("Assisting Hand Assessment"), manual abilities ("ABILHAND-kids") and subjective performance and satisfaction of problematic bimanual activities ("Canadian Occupational Performance Measure") at three time points (pre-treatment, post-treatment, follow-up). This data was analyzed using repeated-measures analysis. RESULTS: Children with Brachial Plexus Birth Injury showed significant improvements on all outcome measures following modified constraint-induced-movement-therapy with bimanual training. These results were comparable to those observed in the group of children with unilateral Cerebral Palsy. DISCUSSION: These results suggest that modified constraint-induced-movement-therapy with bimanual training is effective in Brachial Plexus Birth Injury. They indicate a comparable improved bimanual performance in children with Brachial Plexus Birth Injury than in unilateral Cerebral Palsy and suggests that both groups of children have affectively overcome their developmental disregard.IMPLICATIONS FOR REHABILITATIONChildren with Brachial Plexus Birth Injury frequently experience difficulties in activities of daily living.It has recently been suggested that children with Brachial Plexus Birth Injury may also show a non-use of the affected upper limb despite sufficient capacity, called developmental disregard.Children with Brachial Plexus Birth Injury and developmental disregard might therefore benefit from intensive therapies aimed at overcoming developmental disregard, originally developed for children with unilateral Cerebral Palsy.A combination of modified Constrained-Induced Movement Therapy with intensive Bimanual Training has shown to be affective in children with unilateral Cerebral Palsy.In a small sample, this study shows that a combination of modified Constrained-Induced Movement Therapy with intensive bimanual training is effective in children with Brachial Plexus Birth Injury, comparable and even more than in unilateral Cerebral Palsy.

Windmill-task as a New Quantitative and Objective Assessment for Mirror Movements in Unilateral Cerebral Palsy: A Pilot Study.

OBJECTIVE: To introduce the Windmill-task, a new objective assessment tool to quantify the presence of mirror movements (MMs) in children with unilateral cerebral palsy (UCP), which are typically assessed with the observation-based Woods and Teuber scale (W&T). DESIGN: Prospective, observational, cohort pilot study. SETTING: Children's hospital. PARTICIPANTS: Prospective cohort of children (N=23) with UCP (age range, 6-15y, mean age, 10.5±2.7y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The concurrent validity of the Windmill-task is assessed, and the sensitivity and specificity for MM detection are compared between both assessments. To assess the concurrent validity, Windmill-task data are compared with W&T data using Spearman rank correlations (ρ) for 2 conditions: affected hand moving vs less affected hand moving. Sensitivity and specificity are compared by measuring the mean percentage of children being assessed inconsistently across both assessments. RESULTS: Outcomes of both assessments correlated significantly (affected hand moving: ρ=.520; P=.005; less affected hand moving: ρ=.488; P=.009). However, many children displayed MMs on the Windmill-task, but not on the W&T (sensitivity: affected hand moving: 27.5%; less affected hand moving: 40.6%). Only 2 children displayed MMs on the W&T, but not on the Windmill-task (specificity: affected hand moving: 2.9%; less affected hand moving: 1.4%). CONCLUSIONS: The Windmill-task seems to be a valid tool to assess MMs in children with UCP and has an additional advantage of sensitivity to detect MMs.

Understanding the relationship between brain and upper limb function in children with unilateral motor impairments: A multimodal approach.

Atypical brain development and early brain injury have profound and long lasting impact on the development, skill acquisition, and subsequent independence of a child. Heterogeneity is present at the brain level and at the motor level; particularly with respect to phenomena of bilateral activation and mirrored movements (MMs). In this multiple case study we consider the feasibility of using several modalities to explore the relationship between brain structure and/or activity and hand function: Electroencephalography (EEG), both structural and functional Magnetic Resonance Imaging (sMRI, fMRI), diffusion tensor imaging (DTI), transcranial magnetic stimulation (TMS), Electromyography (EMG) and hand function assessments. METHODS: 15 children with unilateral CP (ages: 9.4 ± 2.5 years) undertook hand function assessments and at least two additional neuroimaging and/or neurophysiological procedures: MRI/DTI/fMRI (n = 13), TMS (n = 11), and/or EEG/EMG (n = 8). During the fMRI scans and EEG measurements, a motor task was performed to study cortical motor control activity during simple hand movements. DTI tractography analysis was used to study the corpus-callosum (CC) and cortico-spinal tracts (CST). TMS was used to study cortico-spinal connectivity pattern. RESULTS: Type and range of severity of brain injury was evident across all levels of manual ability with the highest radiological scores corresponded to children poorer manual ability. Evidence of MMs was found in 7 children, mostly detected when moving the affected hand, and not necessarily corresponding to bilateral brain activation. When moving the affected hand, bilateral brain activation was seen in 6/11 children while 3/11 demonstrated unilateral activation in the contralateral hemisphere, and one child demonstrated motor activation predominantly in the supplementary motor area (SMA). TMS revealed three types of connectivity patterns from the cortex to the affected hand: a contralateral (n = 3), an ipsilateral (n = 4) and a mixed (n = 1) connectivity pattern; again without clear association with MMs. No differences were found between children with and without MMs in lesion scores, motor fMRI laterality indices, CST diffusivity values, and upper limb function. In the genu, midbody, and splenium of the CC, higher fractional anisotropy values were found in children with MMs compared to children without MMs. The EEG data indicated a stronger mu-restoration above the contralateral hemisphere in 6/8 children and above the ipsilateral hemisphere in 2/8 children. CONCLUSION: The current results demonstrate benefits from the use of different modalities when studying upper-limb function in children with CP; not least to accommodate to the variations in tolerance and feasibility of implementation of the differing methods. These exposed multiple individual brain-reorganization patterns corresponding to different functional motor abilities. Additional research is warranted to understand the transactional influences of early brain injury, neuroplasticity and developmental and environmental factors on hand function in order to develop targeted interventions.

The relation between mirror movements and non-use of the affected hand in children with unilateral cerebral palsy.

AIM: In children with unilateral cerebral palsy (CP), it is widely believed that mirror movements contribute to non-use of the affected hand despite preserved capacity, a phenomenon referred to as developmental disregard. We aimed to test whether mirror movements are related to developmental disregard, and to clarify the relation between mirror movements and bimanual function. METHOD: A repetitive squeezing task simultaneously measuring both hands' grip-forces was developed to assess mirror movements by using maximum cross-correlation coefficient (CCCmax ) as well as strength measures (MMstrength ). Developmental disregard, bimanual performance, and capacity were assessed using a validated video-observation method. Twenty-one children with unilateral CP participated (Median age 10y 7mo, interquartile range [IQR] 10y 1mo-12y 9mo). Outcome measures of mirror movements were correlated to developmental disregard, bimanual performance, and capacity scores using Spearman's correlations (significance level: α<0.05). RESULTS: Mirror movements were not related to developmental disregard. However, enhanced mirror movements in the less-affected hand were related to reduced performance (CCCmax : ρ=-0.526, p=0.007; MMstrength : ρ=-0.750, p<0.001) and capacity (CCCmax : ρ=-0.410, p=0.033; MMstrength : ρ=-0.679, p<0.001). These relations were only moderate (performance:MMstrength : ρ=-0.504, p=0.010), low (capacity: MMstrength : ρ=-0.470, p=0.016) or absent for mirror movements in the affected hand. Additionally, seven children showed stronger movements in their less-affected hands when actually being asked to move their affected hand. INTERPRETATION: These findings show no relation between mirror movements and developmental disregard, but support an association between mirror movements and bimanual function.

Event-related Potentials During Target-response Tasks to Study Cognitive Processes of Upper Limb Use in Children with Unilateral Cerebral Palsy.

Unilateral Cerebral Palsy (CP) is a neurodevelopmental disorder that is a very common cause of disability in childhood. It is characterized by unilateral motor impairments that are frequently dominated in the upper limb. In addition to a reduced movement capacity of the affected upper limb, several children with unilateral CP show a reduced awareness of the remaining movement capacity of that limb. This phenomenon of disregarding the preserved capacity of the affected upper limb is regularly referred to as Developmental Disregard (DD). Different theories have been postulated to explain DD, each suggesting slightly different guidelines for therapy. Still, cognitive processes that might additionally contribute to DD in children with unilateral CP have never been directly studied. The current protocol was developed to study cognitive aspects involved in upper limb control in children with unilateral CP with and without DD. This was done by recording event-related potentials (ERPs) extracted from the ongoing EEG during target-response tasks asking for a hand-movement response. ERPs consist of several components, each of them associated with a well-defined cognitive process (e.g., the N1 with early attention processes, the N2 with cognitive control and the P3 with cognitive load and mental effort). Due to its excellent temporal resolution, the ERP technique enables to study several covert cognitive processes preceding overt motor responses and thus allows insight into the cognitive processes that might contribute to the phenomenon of DD. Using this protocol adds a new level of explanation to existing behavioral studies and opens new avenues to the broader implementation of research on cognitive aspects of developmental movement restrictions in children.

Kinematic parameters of hand movement during a disparate bimanual movement task in children with unilateral Cerebral Palsy.

Children with unilateral Cerebral Palsy (uCP) experience problems performing tasks requiring the coordinated use of both hands (bimanual coordination; BC). Additionally, some children with uCP display involuntary symmetrical activation of the opposing hand (mirrored movements). Measures, used to investigate therapy-related improvements focus on the functionality of the affected hand during unimanual or bimanual tasks. None however specifically address spatiotemporal integration of both hands. We explored the kinematics of hand movements during a bimanual task to identify parameters of BC. Thirty-seven children (aged 10.9±2.6years, 20 male) diagnosed with uCP participated. 3D kinematic motion analysis was performed during the task requiring opening of a box with their affected- (AH) or less-affected hand (LAH), and pressing a button inside with the opposite hand. Temporal and spatial components of data were extracted and related to measures of hand function and level of impairment. Total task duration was correlated with the Jebsen-Taylor Test of Hand Function in both conditions (either hand leading with the lid-opening). Spatial accuracy of the LAH when the box was opened with their AH was correlated with outcomes on the Children's Hand Use Experience Questionnaire. Additionally, we found a subgroup of children displaying non-symmetrical movement interference associated with greater movement overlap when their affected hand opened the box. This subgroup also demonstrated decreased use of the affected hand during bimanual tasks. Further investigation of bimanual interference, which goes beyond small scaled symmetrical mirrored movements, is needed to consider its impact on bimanual task performance following early unilateral brain injury.

Neglect-like characteristics of developmental disregard in children with cerebral palsy revealed by event related potentials.

BACKGROUND: Children with unilateral Cerebral Palsy (CP) often show diminished awareness of the remaining capacity of their affected upper limb. This phenomenon is known as Developmental Disregard (DD). DD has been explained by operant conditioning. Alternatively, DD can be described as a developmental delay resulting from a lack of use of the affected hand during crucial developmental periods. We hypothesize that this delay is associated with a general delay in executive functions (EF) related to motor behavior, also known as motor EFs. METHODS: Twenty-four children with unilateral CP participated in this cross-sectional study, twelve of them diagnosed with DD. To test motor EFs, a modified go/nogo task was presented in which cues followed by go- or nogo-stimuli appeared at either the left or right side of a screen. Children had to press a button with the hand corresponding to the side of stimulus presentation. Apart from response accuracy, Event-Related Potentials (ERPs) extracted from the ongoing EEG were used to register covert cognitive processes. ERP N1, P2, N2, and P3 components elicited by cue-, go-, and nogo-stimuli were further analyzed to differentiate between different covert cognitive processes. RESULTS: Children with DD made more errors. With respect to the ERPs, the P3 component to go-stimuli was enhanced in children with DD. This enhancement was related to age, such that younger children with DD showed stronger enhancements. In addition, in DD the N1 component to cue- and go-stimuli was decreased. CONCLUSIONS: The behavioral results show that children with DD experience difficulties when performing the task. The finding of an enhanced P3 component to go-stimuli suggests that these difficulties are due to increased mental effort preceding movement. As age in DD mediated this enhancement, it seems that this increased mental effort is related to a developmental delay. The additional finding of a decreased N1 component in DD furthermore suggests a general diminished visuo-spatial attention. This effect reveals that DD might be a neuropsychological phenomenon similar to post-stroke neglect syndrome that does not resolve during development. These findings suggest that therapies aimed at reducing neglect could be a promising addition to existing therapies for DD.

Unravelling developmental disregard in children with unilateral cerebral palsy by measuring event-related potentials during a simple and complex task.

BACKGROUND: In a subset of children with unilateral Cerebral Palsy (CP) a discrepancy between capacity and performance of the affected upper limb can be observed. This discrepancy is known as Developmental Disregard (DD). Though the phenomenon of DD has been well documented, its underlying cause is still under debate. DD has originally been explained based on principles of operant conditioning. Alternatively, it has been proposed that DD results from a diminished automaticity of movements, resulting in an increased cognitive load when using the affected hand. To investigate the amount of involved cognitive load we studied Event-Related Potentials (ERPs) preceding task-related motor responses during a single-hand capacity and a dual-hand performance task. It was hypothesised that children with DD show alterations related to long-latency ERP components when selecting a response with the affected upper limb, reflecting increased cognitive load in order to generate an adequate response and especially so within the dual-hand task. METHODS: Fifteen children with unilateral CP participated in the study. One of the participants was excluded due to major visual impairments. Seven of the remaining participants displayed DD. The other seven children served as a control group. All participants performed two versions of a cue-target paradigm, a single-hand capacity and a dual-hand performance task. The ERP components linked to target presentation were inspected: the mid-latency P2 component and the consecutive long-latency N2b component. RESULTS: In the dual-hand performance task children with DD showed an enhancement in mean amplitude of the long-latency N2b component when selecting a response with their affected hand. No differences were found regarding the amplitude of the mid-latency P2 component. No differences were observed regarding the single-hand capacity task. The control group did not display any differences in ERPs linked to target evaluation processes between both hands. CONCLUSION: These electrophysiological findings show that DD is associated with increased cognitive load when movements are prepared with the affected hand during a dual-hand performance task. These findings confirm behavioural observations, advance our insights on the neural substrate of DD and have implications for therapy.