Cerebral palsy (CP) is caused by early-stage brain injury, affecting 2 to 3 children in every 1000 live births. CP is divided into different subtypes depending on the dominant neurological signs: spastic, dyskinetic, or ataxic. Epilepsy and intellectual disability, as well as problems with speech, hearing, and vision, are all common complications \[1\]. spastic diplegic CP is one of the most common developmental disabilities throughout life, caused by large-scale changes in subcortical brain activity with a reduced activation of corticospinal and somatosensory circuits, which leads to diminished activation of the central nervous system during volitional activities.

Gait impairment is seen in 90% of children with spastic diplegic CP, stemming from this decreased cortical excitability and compounded by spasticity of the lower extremities, excessive muscular weakness, impaired joint mobility, and poor coordination and balance. Specifically, children with CP have reduced gait velocity, cadence, and stride length, among other affected spatiotemporal gait parameters. The International Classification of Functioning Disability and Health consider changes in the spatial and temporal characteristics of gait to be important predictors to poor function and community participation. Additionally, crouched gait, scissoring, and other atypical gait patterns are common in this population, further affecting the kinematic and kinetic characteristics of gait and leading to metabolically expensive locomotion, high fall risk, and long-term musculoskeletal injury. For children with spastic diplegic CP, the primary goal of rehabilitation is to facilitate mobility and appropriate walking patterns with or without external assistance. Improving spatiotemporal and kinetic characteristics of gait would improve gait function, increase gait efficiency, and reduce the risk of long-term disability. In turn, it would allow these children to participate in more activities of daily living, meaningful interactions with family and society, and environmental exploration, as well as to improve their physical development.

In the current study, the investigators considered two technology-driven strategies that could potentially target gait impairments and improve gait function in children with CP: virtual reality (VR) and transcranial direct current stimulation (tDCS). Both interventions have been studied for their therapeutic potential with mixed results, especially in children. Specifically, VR can simulate real-life activities while providing repetition, augmented sensory input and feedback, error reduction/augmentation to increase motivation during the rehabilitation process. As a training tool, VR provides visual perceptual stimulation resulting from dynamic changes in context, which may aid in the execution of regulated exercises while also requiring concentration and additional postural control. Neuroimaging studies suggest that VR can facilitate learning and recovery by stimulating cortical reorganization and neural plasticity. Previous research has utilized VR as a therapeutic tool for children to improve balance, walking speed, and/or distance, as well as to encourage physical activity. Additional VR therapies have been shown to enhance functional performance in activities including squatting, standing posture, and energy expenditure. With the commercialization of VR-related products like the Nintendo Wii, many virtual games are readily available for home use. These games are often designed to challenge and train balance, posture, and dynamic movements all of which are critical factors for gait. Thus, VR-based rehabilitation may offer a unique, accessible therapeutic approach to reduce gait impairments and improve dynamic function.

In contrast, tDCS is a neuromodulation technique focused on optimizing existing neural pathways to prolong and/or improve the functional gains achieved by rehabilitation. tDCS is applied through either anodal or cathodal stimulation, which corresponds to excitation or inhibition of the stimulated brain areas, respectively. Anodal stimulation enhances cortical excitability through depolarization, allowing for more spontaneous cell firing, while cathodal stimulation has an inhibitory effect through hyperpolarization. Functionally, this means application of tDCS will influence activity in the area of the brain it targets. Previous research indicates that inhibited cortical input to the corticospinal tract is a possible cause of increased spasticity in CP, so it is reasonable to predict that anodal stimulation would mitigate these symptoms in individuals with spastic CP. The neurophysiological effects of anodal tDCS can also potentiate motor learning through this increase in cortical activity, which is applicable to the treatment of all subtypes of CP. These benefits may translate into functionally improved gait as well.