Skilled Bimanual Training Drives Motor Cortex Plasticity in Children With Unilateral Cerebral Palsy

Abstract

Background Intensive bimanual therapy can improve hand function in children with unilateral spastic cerebral palsy (USCP). We compared the effects of structured bimanual skill training versus unstructured bimanual practice on motor outcomes and motor map plasticity in children with USCP. Objective We hypothesized that structured skill training would produce greater motor map plasticity than unstructured practice. Methods Twenty children with USCP (average age 9.5; 12 males) received therapy in a day camp setting, 6 h/day, 5 days/week, for 3 weeks. In structured skill training (n = 10), children performed progressively more difficult movements and practiced functional goals. In unstructured practice (n = 10), children engaged in bimanual activities but did not practice skillful movements or functional goals. We used the Assisting Hand Assessment (AHA), Jebsen-Taylor Test of Hand Function (JTTHF), and Canadian Occupational Performance Measure (COPM) to measure hand function. We used single-pulse transcranial magnetic stimulation to map the representation of first dorsal interosseous and flexor carpi radialis muscles bilaterally. Results Both groups showed significant improvements in bimanual hand use (AHA; P < .05) and hand dexterity (JTTHF; P < .001). However, only the structured skill group showed increases in the size of the affected hand motor map and amplitudes of motor evoked potentials (P < .01). Most children who showed the most functional improvements (COPM) had the largest changes in map size. Conclusions These findings uncover a dichotomy of plasticity: the unstructured practice group improved hand function but did not show changes in motor maps. Skill training is important for driving motor cortex plasticity in children with USCP.

Keywords: hemiplegia; neuroplasticity; pediatric; rehabilitation; transcranial magnetic stimulation.

Figure 1

Changes in skill of the affected hand after intensive bimanual training. Structured and unstructured groups improved equally well in bimanual use of the affected hand (A), movement speed of the affected hand (B), performance of functional goals (C), and satisfaction of performance of functional goals (D). Asterisks indicate within-group differences from baseline to post-intervention time points. * p<0.05, ** p<0.01.

Figure 2

Coronal MRI slices showing a cross-section of each child’s lesion. The color of the frame surrounding the MRI indicates the CST laterality of the child (red = contralateral, blue = bilateral, yellow = ipsilateral). The yellow asterisk indicates the side of injury.

Figure 3

Changes in motor maps after training. Colored dots represent movement evoked by TMS at that site.A1-C1. Structured skill training, representative maps of the affected hand from one child. A2-C2. Unstructured practice, representative maps of the affected hand from one child. D. Quantification of map changes. The size of the motor map of the affected hand increased significantly only in the structured training group (* p<0.05).

Figure 4

Changes in magnitude of motor evoked potentials in TMS maps after structured skill training. A1-C1. Maps of the affected hand located contralateral to the affected hemisphere in a representative case. Red color indicates stronger MEP response. A2-C2. Representative maps of the affected hand in a representative case from the unstructured practice group. D-E. MEP amplitude of the representation of the affected FDI increased significantly after structured but not unstructured training (* p<0.05).