Anteroposterior balance reactions in children with spastic cerebral palsy

Quiet standing and anteroposterior limits of stability in adolescents and young adults with bilateral spastic cerebral palsy

Stance stability in individuals with bilateral spastic cerebral palsy (BSCP) in various standing postures including the quiet standing (QS) and limits of stability (LoS) has been widely studied. However, the relationships between the QS and LoS remain unclear. This study aimed to determine the relationships between the positions and postural sway in the QS and anteroposterior LoS in individuals with BSCP. It included 27 adolescents and young adults with BSCP (BSCP group) and 27 adolescents and young adults without disability (control group). The position of center of pressure in the anteroposterior direction (CoPy position) and the path length of center of pressure (CoP path length) during the QS and the anterior and posterior LoS (A-LoS and P-LoS, respectively) were measured using a force platform. The CoPy positions in the A-LoS and P-LoS in the BSCP group were limited compared with those in the control group. In the BSCP group, the more anterior the CoPy position in the QS, the more anterior (i.e., limited) it was in the P-LoS. Although the CoP path length in the QS was larger in the BSCP group, those in the A-LoS and P-LoS were larger in the control group. The BSCP group also showed that the more anterior the CoPy position or the longer the CoP path length in the QS, the more decreased the anteroposterior LoS range was. Therefore, assessing various standing postures, including QS and anteroposterior LoS, is important to manage balance impairments in individuals with BSCP.

Effect of the Dynamic Orthotic Garment on Postural Control, and Endurance in Children with Spastic Diplegic Cerebral Palsy: A Randomized Controlled Trial

Purpose

To investigate the effect of dynamic orthotic garments (Thera togs) on foot pressure distribution, postural control, and endurance in children with spastic diplegic CP.

Patients and Methods

This is a single-blind randomized controlled clinical trial involving 34 (8-10 years) with spastic diplegic CP. The control group received conventional physical therapy (CPT), whereas the study group received CPT in addition to wearing TheraTogs. We recorded foot pressure distribution, trunk control measurement scale, trunk position sense, Pediatric Berg Balance Scale (PBS), and six-minute walking distance (6MWD).

Results

Both groups showed improvement. The study group had significant improvement in foot pressure distribution (p-value 0.003, 0.001, <0.001 for forefoot, midfoot, and rearfoot mean pressures respectively, and 0.005, <0.001, and 0.005 for forefoot, midfoot, and rearfoot peak pressures respectively), Pediatric balance scale, The trunk control measurement scale, and Trunk position sense (p-value < 0.001) and six-minute walking distance (p-value 0.029). Our data suggest that adding TheraTogs to conventional physiotherapy improves foot pressure, postural control, and endurance in children with spastic diplegic cerebral palsy.

Conclusion

Both TheraTogs and conventional physical therapy corrected foot pressure distribution, trunk control, improved balance, and increased 6MWD in children with spastic diplegic CP but the improvement was more significant in TheraTogs group.

Clinical Trial Registration

NCT05271149.

Increased muscle responses to balance perturbations in children with cerebral palsy can be explained by increased sensitivity to center of mass movement

BACKGROUND

Balance impairments are common in children with cerebral palsy (CP). Muscle activity during perturbed standing is higher in children with CP than in typically developing (TD) children, but we know surprisingly little about how sensorimotor processes for balance control are altered in CP. Sensorimotor processing refers to how the nervous system translates incoming sensory information about body motion into motor commands to activate muscles. In healthy adults, muscle activity in response to backward support-surface translations during standing can be reconstructed by center of mass (CoM) feedback, i.e., by a linear combination of delayed (due to neural transmission times) CoM displacement, velocity, and acceleration. The level of muscle activity in relation to changes in CoM kinematics, i.e., the feedback gains, provides a metric of the sensitivity of the muscle response to CoM perturbations.

RESEARCH QUESTION

Can CoM feedback explain reactive muscle activity in children with CP, yet with higher feedback gains than in TD children?

METHODS

We perturbed standing balance by backward support-surface translations of different magnitudes in 20 children with CP and 20 age-matched TD children and investigated CoM feedback pathways underlying reactive muscle activity in the triceps surae and tibialis anterior.

RESULTS

Reactive muscle activity could be reconstructed by delayed feedback of CoM kinematics and hence similar sensorimotor pathways might underlie balance control in children with CP and TD children. However, sensitivities of both agonistic and antagonistic muscle activity to CoM displacement and velocity were higher in children with CP than in TD children. The increased sensitivity of balance correcting responses to CoM movement might explain the stiffer kinematic response, i.e., smaller CoM movement, observed in children with CP.

SIGNIFICANCE

The sensorimotor model used here provided unique insights into how CP affects neural processing underlying balance control. Sensorimotor sensitivities might be a useful metric to diagnose balance impairments.

Voluntary muscle coactivation in quiet standing elicits reciprocal rather than coactive agonist-antagonist control of reactive balance

Muscle coactivation increases in challenging balance conditions as well as with advanced age and mobility impairments. Increased muscle coactivation can occur both in anticipation of (feedforward) and in reaction to (feedback) perturbations, however, the causal relationship between feedforward and feedback muscle coactivation remains elusive. Here, we hypothesized that feedforward muscle coactivation would increase both the body's initial mechanical resistance due to muscle intrinsic properties and the later feedback-mediated muscle coactivation in response to postural perturbations. Young adults voluntarily increased leg muscle coactivation using visual biofeedback before support-surface perturbations. In contrast to our hypothesis, feedforward muscle coactivation did not increase the body's initial intrinsic resistance to perturbations, nor did it increase feedback muscle coactivation. Rather, perturbations with feedforward muscle coactivation elicited a medium- to long-latency increase of feedback-mediated agonist activity but a decrease of feedback-mediated antagonist activity. This reciprocal rather than coactivation effect on ankle agonist and antagonist muscles enabled faster reactive ankle torque generation, reduced ankle dorsiflexion, and reduced center of mass (CoM) motion. We conclude that in young adults, voluntary feedforward muscle coactivation can be independently modulated with respect to feedback-mediated muscle coactivation. Furthermore, our findings suggest feedforward muscle coactivation may be useful for enabling quicker joint torque generation through reciprocal, rather than coactivated, agonist-antagonist feedback muscle activity. As such our results suggest that behavioral context is critical to whether muscle coactivation functions to increase agility versus stability.NEW & NOTEWORTHY Feedforward and feedback muscle coactivation are commonly observed in older and mobility impaired adults and are considered strategies to improve stability by increasing body stiffness prior to and in response to perturbations. In young adults, voluntary feedforward coactivation does not necessarily increase feedback coactivation in response to perturbations. Instead, feedforward coactivation enabled faster ankle torques through reciprocal agonist-antagonist muscle activity. As such, coactivation may promote either agility or stability depending on the behavioral context.

Individuals with cerebral palsy show altered responses to visual perturbations during walking

Individuals with cerebral palsy (CP) have deficits in processing of somatosensory and proprioceptive information. To compensate for these deficits, they tend to rely on vision over proprioception in single plane upper and lower limb movements and in standing. It is not known whether this also applies to walking, an activity where the threat to balance is higher. Through this study, we used visual perturbations to understand how individuals with and without CP integrate visual input for walking balance control. Additionally, we probed the balance mechanisms driving the responses to the visual perturbations. More specifically, we investigated differences in the use of ankle roll response i.e., the use of ankle inversion, and the foot placement response, i.e., stepping in the direction of perceived fall. Thirty-four participants (17 CP, 17 age-and sex-matched typically developing controls or TD) were recruited. Participants walked on a self-paced treadmill in a virtual reality environment. Intermittently, the virtual scene was rotated in the frontal plane to induce the sensation of a sideways fall. Our results showed that compared to their TD peers, the overall body sway in response to the visual perturbations was magnified and delayed in CP group, implying that they were more affected by changes in visual cues and relied more so on visual information for walking balance control. Also, the CP group showed a lack of ankle response, through a significantly reduced ankle inversion on the affected side compared to the TD group. The CP group showed a higher foot placement response compared to the TD group immediately following the visual perturbations. Thus, individuals with CP showed a dominant proximal foot placement strategy and diminished ankle roll response, suggestive of a reliance on proximal over distal control of walking balance in individuals with CP.

Parental subjective assessment of gait limitations: Comparison with objective gait variables

BACKGROUND

Subjective assessment is an important part of clinical examination providing quality insights into impairments of body structure and functions. Research into the associations between parental perceptions of gait in children with cerebral palsy (CP) and objective clinical gait measures is limited.

RESEARCH QUESTION

What are the parental perceived gait limitations in children with CP and are these perceptions associated with objective clinical gait analysis?

METHODS

Parent questionnaires were retrospectively analysed for children with CP who attended our gait analysis laboratory over a 24-month period. Perceived walking limitations caused by pain, weakness, lack of endurance, mental ability, safety concerns, and balance were recorded on a 5-point Likert scale. Normalised gait speed, normalised step length and the Gait Deviation Index (GDI) were calculated. Differences between responses were assessed using Chi-squared tests with Dunn's post hoc test with Bonferroni adjustment. Spearman's rank correlations were performed to determine the relationship between responses and gait parameters.

RESULTS

Data from 251 participants were included, mean age 9 ± 3.4 years, Gross Motor Function Classification System (GMFCS) level I = 158, II = 64 and III = 29. Balance was perceived to limit walking to the greatest extent, followed by weakness, lack of endurance, safety concerns, pain and mental ability. This rank was consistent across GMFCS levels I, II and III. Perceived balance limitations showed the strongest correlations with objective gait variables, GDI (r = -0.31 p = 0.000), normalised step length (r = -0.30 p = 0.0000) and normalised gait speed (r = -0.24 p = 0.0001).

SIGNIFICANCE

Subjective gait perceptions provide a valuable indication of gait function but are weakly associated with objective clinical gait analysis. Outcome measures that are sensitive to changes in balance may be more responsive to parental concerns and help to satisfy their goals and expectations.

Reliability, minimum detectable change, and minimum clinically important difference of the balance subtest of the Bruininks-Oseretsky test of motor proficiency-second edition in children with cerebral palsy

PURPOSE

This study aimed to investigate the internal consistency, inter-rater, and test-retest reliability of the balance subtest of the Bruininks-Oseretsky test of motor proficiency-second edition (BOT-2) and to estimate the minimum detectable change (MDC) and minimum clinically important difference (MCID) of the balance subtest of the BOT-2 in children with cerebral palsy (CP).

METHODS

In total, 20 children with CP participated in the present study. Internal consistency, test-retest, and inter-rater reliability were computed to establish reliability of the balance subtest of the BOT-2. The MDC95 was estimated from the standard error of measurement (SEM) to determine a real change for an individual child with CP. The anchor- and distribution-based MCID were calculated to determine the smallest change that might be important to clinicians. For concurrent validity, the correlation between the balance subtest of the BOT-2 and the pediatric balance scale (PBS) were calculated using Spearman's correlation.

RESULTS

Internal consistency was good (Cronbach's alpha coefficient = 0.89). The BOT-2 had excellent test-retest (ICC = 0.99, p < 0.001) and inter-rater reliability (ICC = 0.99, p < 0.001). The balance subtest of the BOT-2 had an SEM of 0.70, MDC95 of 9.61, and MCIDs of 2.54 (anchor-based) and 1.38 (distribution-based). Additionally, there was a moderate positive correlation between the balance subtest of the BOT-2 and the PBS (Spearman's rho = 0.629, p = 0.003).

CONCLUSIONS

Our experimental results indicate that the balance subtest of the BOT-2 had good internal consistency, along with excellent test-retest and inter-rater reliability. The change in scores of an individual child with CP should attain 9.61 points on the balance subtest of the BOT-2 to indicate a clinically important change. The MDC95 and MCID values could be helpful in understanding therapeutic effects and evaluating balancing ability using the balance subtest of the BOT-2 in children with CP.

The construct and concurrent validity of brief standing sway assessments in children with and without cerebral palsy

BACKGROUND

Standing postural sway is often quantified from center of pressure trajectories. During assessments of longer durations, children may fidget, thus limiting the feasibility and validity of sway recordings.

RESEARCH QUESTION

Do postural sway sample durations less than 30 s maintain construct and concurrent validity?

METHODS

In this case-control, observational study, we measured postural sway in 41 children (age 5-12 years, 23 typically developing (TD); 18 with spastic cerebral palsy (CP), 13 diplegic and 5 hemiplegic, 11 GMFCS level I and 7 level II) for 30-second eyes-opened and eyes-closed conditions. From a single recording, 5-second incremental durations of 5-30 s were considered in this analysis. We quantified anteroposterior, mediolateral, and transverse-plane sway using seven time-domain variables: root-mean-square error, total excursion, mean frequency, mean distance, sway area, and 95 % confidence circle and ellipse areas. Variables were calculated in eyes-opened and eyes-closed conditions, as well as the ratio of the two. Construct validity was evaluated by the persistence of large effect sizes (Glass's Δ ≥ 0.80) between CP and TD participants at shorter durations than 30 s. Concurrent validity was evaluated by the correlations of shorter duration measures to the 30 s measure.

RESULTS

Seven sway measures had large between-group effects (Glass's Δ ≥ 1.02) for the 30 s measure that persisted (Glass's Δ ≥ 0.81) at shorter durations (5-25 s) and also maintained concurrent validity (r ≥ 0.83). Six of these seven measures were taken in the eyes-closed condition, and all seven measures were in the mediolateral direction or transverse plane.

SIGNIFICANCE

Our analysis suggests that sway durations less than 30 s can uphold construct and concurrent validity. These measures were primarily in the eyes-closed conditions and mediolateral direction. These results are a promising indicator that shorter-duration sway measures may be of utility when fidgeting prevents longer recordings.

Balance confidence and physical activity participation of independently ambulatory youth with cerebral palsy: an exploration of youths' and parents' perspectives

AIM

Youth with cerebral palsy generally participate in less physical activity than typically developing peers. In adults with physical disabilities, balance confidence is a strong predictor of participation and community re-integration. However, balance confidence has not been studied in youth with cerebral palsy.

METHOD

Qualitative descriptive methodology with interviews of eight youth with cerebral palsy (9-17 years old, three girls) in Gross Motor Function Classification System Levels I-III, and eight parents (five mothers) of youth with cerebral palsy (9-17 years old, two girls) in Levels I-III.

RESULTS

Three themes arose: (1) youth in Gross Motor Function Classification System Levels I-II are more concerned about losing their balance during physical activities than those in Level III; (2) when balance is lost, embarrassment and frustration are more common than fear, especially for those in Levels I-II; and (3) social factors can create a favorable participation environment when balance confidence is low, especially for youth in Levels I-II.

CONCLUSION

Balance confidence may have greater influence on physical activity participation for youth in Gross Motor Function Classification System Levels I-II than those in Level III. Youth in Levels I-II may draw greater benefit from interventions targeting balance confidence when addressing physical activity goals.IMPLICATIONS FOR REHABILITATIONBalance confidence may have a greater influence on activity avoidance for youth with cerebral palsy in Gross Motor Function Classification System Levels I and II (who are independently ambulatory without walkers or cane(s)) than for those in Level II (who use walkers or cane(s) to ambulate).Youth who are independently ambulatory without walkers or cane(s) may benefit more from interventions directed at balance confidence (e.g., enactive mastery and verbal persuasion) to address their physical activity participation goals.For youth who are independently ambulatory without walkers or cane(s), addressing factors that could reduce the influence of balance confidence on physical activity participation, such as providing a positive and supportive social environment in which to participate, may be beneficial.