Abstract
Children with unilateral cerebral palsy (CP) walk independently although with an asymmetrical, more poorly coordinated pattern compared to their peers. While gait biomechanics in unilateral CP and their alteration from those without CP have been well documented, cortical mechanisms underlying gait remain inadequately understood. To the best of our knowledge, this is the first study utilizing electroencephalography (EEG) during treadmill gait in older children with and without CP. Lower limb surface electromyographic (EMG) data were collected and muscle synergy analyses performed to quantify motor output. Our primary goal was to evaluate the relationships between cortical and muscle activation within and across groups and hemispheres to provide novel insights into neural control of gait and how it may be disrupted by an early unilateral brain injury. Participants included 9 children with unilateral CP, mean age 16.0 ± 2.7 years, and 12 with typical development (TD), mean age 14.8 ± 3.0 years. EEG data were collected during a standing baseline and treadmill walking at self-selected speed. EMG of 16 lower limb muscles were also collected bilaterally and synchronized with EEG. No significant group differences were found in synergy number or structure across groups. Six cortical clusters were identified as having gait-related activation and all contained participants from both CP and TD groups; however, the percent of individuals per group appearing in different clusters varied. Notably, the cluster least represented in CP was the non-dominant motor region. Both groups showed mu-band ERD in the motor clusters during gait although sustained beta-band ERD was not evident in TD. The CP group showed greater cortical activation than TD during walking as measured by mu- and beta-ERD in the dominant and non-dominant motor and parietal regions and elevated low gamma-activity in the frontal and parietal areas, a unique finding in CP. CP showed greater bilateral motor EEG-EMG coherence in the gamma-band with the hallucis longus compared to TD. In summary, individuals with CP display increased cortical activation during gait possibly relating to differences in distal motor control of the more affected side. Strategies that iteratively reduce cortical activation while improving selective motor control are needed in CP.
Highlights
Cerebral palsy (CP) describes a group of functional motor disabilities that are the consequences of brain injuries early in development
Non-dominant limb stance time relative to the gait cycle was significantly lower in the cerebral palsy (CP) group (TD: 67.2 ± 0.90%, CP: 64.2 ± 2.30%; p < 0.001) with no significant difference in dominant limb stance time between groups (Table 2)
There were no significant differences in mean treadmill speed, normalized step length and cadence between groups (Table 2), mean walking speed (TD: 0.99 ± 0.11 m/s, CP: 0.89 ± 0.10 m/s; p = 0.053), non-dominant step length (TD: 0.30 ± 0.02, CP: 0.29 ± 0.02; p = 0.052), and non-dominant limb cadence (TD: 104 ± 5.74 step/min, CP: 96.1 ± 10.9 steps/min; p = 0.055) were all greater in typical development (TD), but failed to reach statistical threshold
Summary
Cerebral palsy (CP) describes a group of functional motor disabilities that are the consequences of brain injuries early in development. Movement difficulties may be predominantly unilateral (one side of the body) or bilateral (both sides), and the range of disability can vary from mild coordination problems to being totally dependent for mobility and care, as categorized by the Gross Motor Functional Classification System (GMFCS) (Palisano et al, 1997). Most children with unilateral CP learn to walk independently. Their motor patterns and coordination differ from their peers without CP with distal limb involvement most prominent (Winters et al, 1987). The advancement of mobile neuroimaging technologies [e.g., functional near infrared spectroscopy (fNIRS) and electroencephalography (EEG)] and associated signal processing techniques have provided novel insights on the role of cortical activity in walking. Walking tasks of greater complexity (Koenraadt et al, 2014) or requiring increased precision (Kurz et al, 2012) have been shown to further elevate hemodynamic activity
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