## 1 Introduction  
Paediatric brain damage includes every brain injury that happens during gestation or early years of life to childhood and adolescence [1; 2; 3], and includes conditions such as cerebral palsy (CP) and paediatric acquired brain injury [1; 4]. The sequelae of paediatric brain injuries manifest a broad spectrum of motor and cognitive deficits, adversely affecting a child's ability to perform everyday tasks [2]. Motor impairments compromise critical functions such as gait, posture, and the use of upper limbs (UL) [5]. Cognitive deficits have a direct impact on communication, social engagement, and participation [6; 7; 8; 9]. Although motor and cognitive rehabilitation have traditionally been approached as separate entities, burgeoning evidence underscores the intricate interplay between cognitive and motor domains, highlighting their collective influence on motor planning and execution [10; 11; 12]. Notably, greater manual dexterity is associated with better cognitive function in children with CP [10]. The profound impact of UL motor impairments on the autonomy of children in daily living activities underscores the need for integrated neurorehabilitation strategies that address both motor and cognitive challenges [13]. Neuroplasticity plays a pivotal role in neurorehabilitation by driving the neural adaptations responsible for the development or restitution of function following brain injury [14]. Spontaneous neuroplastic changes often occur in the initial months post-injury, contributing to early symptomatic improvements. Interventions during the acute phase may amplify these inherent mechanisms. Despite the application of transdisciplinary rehabilitative approaches [15; 16], a plateau in functional gains typically manifests during the chronic phase, where motor and cognitive deficits tend to persist. To overcome this plateau, strategies such as virtual reality (VR) and transcranial direct current stimulation (tDCS) have been deployed. These techniques have demonstrated efficacy in enhancing UL functionality across various stages of brain injury recovery [17; 18; 19; 20]. VR allows the practice of repetitive tasks with immediate feedback on performance in an artificial environment similar to the real one, which is essential for learning processes. Specifically for children, game-based approaches add an extra motivation with task-related rewards and enlarge focused attentional span [17; 21]. A good example is the Rehabilitation Gaming System (RGS) ([PERSON], Barcelona, Spain), which is a VR-based rehabilitation that considers both motor and cognitive aspects for UL rehabilitation with a wide range of task difficulty calibration. This program captures the specific features of the impaired limbs and adapts the task parameters to them [22]. Several studies have shown the effectiveness of VR in paediatric brain damage both in motor and cognitive skills [18; 23; 24; 25; 26]. Combined motor and cognitive RV protocols seem to yield better functioning results in both domains [25; 27]. On the other hand, tDCS is one of the most used non-invasive brain stimulation techniques, as it has shown to be secure and effective [28] when applied in conjunction with other techniques, in motor [29] and cognitive outcomes [30; 31] in paediatric brain damage. tDCS consists of applying a low intensity current (1-2 mA) to the skull [32] with two or more electrodes. There are several montages according to the aim of the stimulation application, which varies in electrode size, number of electrodes, and its placement. Bipolar tDCS is the most common montage nowadays, but high-definition tDCS, involving a greater number of electrodes, emerges as a tool for improving focality of the stimulation effects [33]. tDCS mechanism of action is based on changing the action potential threshold, either increasing it with anodal stimulation, or decreasing it with cathodal stimulation. The electrodes can be displayed stimulating one hemisphere or both of them in a bi-hemispheric approach [34].