This represents one of the two RCTs of the project "Bottom-up and tOp-down neuromOdulation of motor plaSTicity in cerebral palsy" (BOOST; FRRB 3438840). The study will be a randomized, sham controlled, pre-test/post-test study involving 44 children and adolescents with CP. Patients will be treated in pairs, with a matching of motor deficit severity, IQ, and age. Each pair will be randomly assigned to the active or to the sham tVNS group, stratifying the pairs between the two groups based on motor deficit severity, IQ, and age. Both groups will undergo a bimanual training in an ecological and highly motivating environment during the application of the tVNS. During the training, starting from a set of proposals the choice of the type of activities to be practiced in each session will be left to patients, boosting the motivational aspect of the training. This will also ensure an individualized and goal directed approach. The therapists will monitor and modify the activities within each pair to ensure that the intervention maintains the quality of the individualized intervention. The positions performed during bimanual tasks and the activities of daily living will be designed to systematically engage postural control of the trunk and lower limbs according to Habit-ILE protocol. The rehabilitation treatment will be carried out for 5 consecutive days for 3h/day for 2 weeks (30 hours of intervention overall). Children and adolescents will be assessed before the start of treatment (T0), immediately after the end of intensive treatment (T1) and three months after the end (T2). The overall RCT will be structured as follows. In the first session prior the beginning of the training (t0), the RCT will include the administration of all clinical assessment measures and the patients will be asked to perform for 10 minutes an ad-hoc computer based Visuomotor task (please refer to the outcome sessions for more detailed description). Then, patients will undergo the 10 days treatment. For each training day, the treatment will last three hours. During the first 75 minutes of treatment the active or sham tVNS (according to the group allocation) will be delivered. Before starting, 20 minutes after and soon after the end of the stimulation the vital parameters will be checked. After the end of the stimulation, patients will be also asked to rate the sensations experienced during the stimulation through Visual Analogue Scales and through child-friendly Likert scales. Then, they will continue the training for the remaining session time without stimulation. Soon after the end of all the training sessions, patients will carry the t1 evaluation. As for the t0 session, this session will include the administration of the clinical assessment measures and execution for 10 minutes of the Visuomotor task. Three months after the end of the training (t2) the follow up assessment will be conducted, following the same exact procedure of t0.

Primary outcomes will include the following clinical measures: the Assisting Hand Assessment (AHA), the Box and Block Test (BBT) and the performance at the Visuomotor task. Secondary outcomes will include the scores at the following tests: the Children's Hand Experience Questionnaire (CHEQ), the Canadian Occupational Performance Measure (COPM), the Gross Motor Function Measure (GMFM-66); the Melbourne Assessment-2 (MA2) scale, the Vineland Adaptive Behavior Scale Version 2 (VABS II), the Pediatric Quality of Life Inventory (PEDS-QL). Vital parameters (the oxygen saturation (SPO2) and the Heart Rate (HR)), and the scores at the questionnaires assessing stimulation- induced sensations will be also checked to assess the safety and the tolerability of the stimulation. Lastly, the feasibility and the acceptability of the training will be assessed by considering, respectively, the number of patients completing the training/the number of sessions for each patient and the response to ad hoc questionnaires for the patients and their guardians.

All primary and secondary outcomes will be collected at each time point, except for the PEDS-QL and VABS II, which will be administered only at T0 and T2. Furthermore, vital parameters and the questionnaires assessing stimulation-induced sensations will be examined during each stimulation session. The acceptability questionnaires will be administered only after the end of the training (t1).

The patients and their guardians, the personnel responsible for conducting the bimanual training and analysing clinical data will be kept blind to the group allocation. Instead, the coordinator of the study, the staff who will apply the tVNS will be "not blind". With respect to the clinical assessment, whenever possible the staff administering and scoring the scales will be blinded to group allocation. Questionnaire scores and neuropsychological tests will not contain personal information about the subjects, who will be identified by an alphanumeric code. All records that contain names or other personal identifiers, such as informed consent forms, will be stored separately from study records identified by code number. In order to uphold the overall quality of the clinical trial, instances of code breaks should be limited to exceptional circumstances, where knowledge of the actual treatment is deemed absolutely necessary for the ongoing management of the patient.

The intensive treatment will take place at IRCCS E. Medea "Associazione La Nostra Famiglia" in Bosisio Parini (Lecco), at Fondazione Mondino IRCCS (Pavia) and at ASST Ospedali Civili di Brescia.

This trial is supported by Fondazione Regionale per la Ricerca Biomedica (Regione Lombardia), project FRRB 3438840 BOOST "Bottom-up and tOp-down neuromOdulation of motor plaSTicity in cerebral palsy"