**1. Introduction**

Congenital Zika syndrome (CZS) became a global concern after the Zika virus outbreak in 2015, which mainly affected Brazil [1]. The situation is more serious in the Northeast region, which concentrates the majority of cases, and is marked by strong social problems, scarcity of investments in the training of human resources and in the provision of health services [2]. Children with CZS have severe motor disability, the majority of them compatible with Gross Motor Function Classification System (GMFCS) classification V (i.e., no prognosis for independent mobility) [3]. Only one study evaluated the profile of functioning of children with CZS in Brazil, demonstrating that activity and participation were highly impacted, and that societal attitude was the main barrier to participation [4]. To date, only one preliminary study has been published on the rehabilitation of children with CZS between 3 and 9 months of age. The results indicated that the intervention program based on the principles of Goals-Activity-Motor Enrichment (GAME) improved mothers' assessment of their babies' performance, and satisfaction with the performance of functional priorities and the perception of an enriched home environment [5].

As CZS is a completely new condition, rehabilitation approaches more commonly used are based on recommendations for cerebral palsy (CP). Even for CP, evidence-based interventions are more easily available for children with mild to moderate motor impairment, and interventions are limited for children with severe motor impairment [2,6]. Young children with typical development exhibit gains in cognitive development, communication, and social skills after starting independent walking [7–9]. Young children with motor disabilities are often not able to take part in self-initiated mobility, and are more likely to experience cognitive and developmental delays, as well as less social interactions with caregivers and peers [10,11].

For young children with disabilities, early powered mobility may advance the body function, activity, and participation, in contrast to other interventions within pediatric rehabilitation which are often focused exclusively on one physical skill (body structure domain) in isolation of other therapeutic goals within a stagnant clinical environment (ex. treadmill training). Research indicates positive results of powered mobility interventions for young children with functional impairments [11,12] since battery-operated ride-on cars are easily modified and are considered as an option of increasing interest for motorized mobility for children with disabilities.

Globally, there are very few commercially available motorized wheelchairs for young children with disabilities and existing options are extremely expensive (>USD 17,000 for a base model) [13]. Environmental inaccessibility and device characteristics inhibits motorized wheelchair use [12–15].

The low cost of modified cars (<USD 400) can minimize some of the barriers previously reported, such as an inaccessible physical environment, financial impact, and peculiarities of motorized wheelchairs readily available commercially. The modifications are fundamental and include the use of large and easy-to-press actuators generally positioned on the steering wheel; in addition to the requirements to provide stability in the seat using common materials, such as polyvinyl chloride (PVC) pipe, swimming kickboards, and Velcro.

Several studies have showed the results of a powered mobility intervention with modified ride-on car on the behavior and development of young children with disabilities, including CP. Although none of the children in these studies were formally referred to use powered mobility devices due to their young age or diagnosis, all demonstrated the ability to independently press the activation switch, enjoyed driving sessions, and some experienced increased self-care mobility [16], social skills [16,17], as well as increased peer interaction on the playground [18], and during an inclusive playgroup [19]. The limitations of previous work includes a heavy reliance on low-evidence level research designs (i.e., case reports and case series); the inclusion of participants with varying disabilities in the same sample; and the reporting of a wide variety and often very low adherence rates to recommended use guidelines. These limitations have hindered the interpretation and generalization of study results and will be addressed in the current protocol.

Although participation-based interventions are a promising strategy not only to improve participation but also body functions [20], there are no evidenced-based practices to guide clinical recommendations of early powered mobility device use, including modified ride-on cars, for young children with disabilities, including CZS. The current protocol will address this gap in knowledge and will have a direct and immediate impact on clinical practice. From a global health standpoint, the results may provide an evidence-based rehabilitation option that will be relevant to early child development in low resource contexts. The objective of this study is to determine the feasibility of a

powered mobility intervention for young children with CZS with severe motor impairment including acceptability and effectiveness. The specific aims are:

