(D-156) Effects of Hand Arm Bimanual Intensive Therapy on Corticospinal Reorganization and Motor Cortex Plasticity in Children with Unilateral Cerebral Palsy

Introduction:: Cerebral palsy (CP), a prevalent childhood motor disorder, affects approximately 3.6 out of 1000 children [1]. Unilateral CP results in sensorimotor deficits lateralized to one side of the body, primarily due to damage of the corticospinal tract (CST). In typically developing children, the CST innervates the contralateral side of the body. Hence, the CST from the right hemisphere controls the left side of the body. However, due to the early brain damage, children with UCP exhibit maladaptive plasticity often resulting in ipsilateral/contralesional and bilateral innervations to the affected hand and reduced motor cortex excitability. There is conflicting evidence whether maladaptive plasticity contributes to more severe dysfunction in children with UCP. Furthermore, the effects of intensive therapy on CST reorganization and motor cortex plasticity are unclear. Hence, the purposes of this study were: 1) to assess the impact of maladaptive plasticity on hand function and 2) to assess the effects of hand arm bimanual intensive therapy (HABIT) on motor cortex plasticity and CST organization in children with UCP.

Materials and Methods:: 12 children with UCP, aged 6 to 16 years were included in this study. We analyzed motor cortex plasticity and determined CST organization based on transcranial magnetic stimulation (TMS) assessments such as recruitment curve (IO) and resting motor threshold (RMT). We also assessed hand function using the Box and Block Test (BBT), Nine-hole Peg Test (NHPT) and Jebsen Hand Function Test (JHFT). Bimanual hand use was examined using the accelerometry measure, use ratio (UR) defined as affected hand usage divided by unaffected hand usage. All children received task-specific HABIT introduced in a playful setting for 30 hours (6 hrs/day for 5 days). Pre- and post-HABIT TMS and hand function assessments were performed. We analyzed motor cortex plasticity and determined CST organization based on TMS assessments. We determined the CST organization based on the presence or absence of motor evoked potential (MEP) of at least 25 µV from the affected hand after stimulating the affected and the unaffected motor cortex. Presence of MEPs from the affected hand after stimulating the unaffected cortex indicates contralesional CST organization likewise presence of MEPs from the affected hand after stimulating the affected as well as unaffected cortex indicates bilateral CST organization. The TMS data collected was then processed using the MATLAB-based TMS Analysis ToolBox. Descriptive analysis of the assessments and correlation values between RMT and hand assessments were calculated.

Results, Conclusions, and Discussions::

Results/Discussion: All the participating children demonstrated contralesional CST organization at baseline. The average unaffected cortex RMT was 68±13.1. There was a significant negative correlation between the RMT and NHPT (R=0.43, P=0.05) and UR (R= -0.27, P=0.04). Children with reduced motor cortex excitability indicated by higher RMT had greater impairments in fine motor and bimanual function, respectively. Post-HABIT, 66% of the participating children had a positive shift from contralesional to bilateral CST organization. There was a significant decrease in RMT from pre- to post-HABIT, which indicates an increase in motor cortex excitability after intensive therapy. Additionally, area under the recruitment curve increased from pre- 6.44±5.95 to post-HABIT 9.52±8.41, which further indicates an increase in motor cortex excitability after HABIT. Post-HABIT, there were also significant improvements in gross motor function (BBT change score= 3±1.3 blocks), fine motor function (NHPT change score= -15.95±58.19 sec, JHFT change score= -23.2±33.7 sec), bimanual hand use (UR change score= 0.04±0.08).

Conclusion: The study findings suggest that reduced excitability of the motor cortex is associated with greater severity of the affected hand function, specifically in fine motor coordination and bimanual hand use areas. HABIT has the potential to enhance motor cortex excitability, to alter the CST organization lateralized to the affected cortex, and to enhance hand function of children with UCP.

Acknowledgements (Optional): :

This material is based upon work supported by the National Science Foundation under Grant No. 1950507. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

References (Optional): :

[1] Smorenburg A et. al. Neurohabilt (2016). 31(3) 250-260.

[2] Friel K et. al. Neurohabilt (2016). 30(9) 834-844.

[3] Rich T et. al. Clin EEG Neurosci (2020). 51(3) 185-190.

[4] Kuo H et. al. DMCN (2016). 59(1) 65-71.

[5] Nardone R et. al. NCCN (2021). 51(5) 391-408