Acquired Brain injury (ABI) is the main cause of death and disability among young adults . ABI can cause from mild to severe impairments in cognitive, motor or psychological functions leading to difficulties in familiar, vocational and social reintegration which diminishes health-related quality of life . Among them, ABI can cause different levels of paralysis, such as hemiplegia or hemiparesis, which dramatically affect the balance control and, consequently, the performance of activities of daily living (ADL). Traditional balance training is based on the automatic repetition of specific movements. These methods can become repetitive and aimless, and thus reduce the motivation and adherence to treatment. Balance control, as the complex constellation of impairments following ABI, demands a multidisciplinary rehabilitation approach that, with the aid of new technologies, could maximize functional recovery.
In the last few years, there has been increasing research interest in the application of virtual reality (VR) technology to rehabilitation . In contrast with traditional rehabilitation procedures, which may be tedious, resource-intensive and costly, VR provides patients with ABI opportunities to engage in meaningful, intensive, enjoyable and purposeful tasks related to real-life interests and ADL . The published clinical results indicate that the recovery of motor function in ABI patients with motor difficulties appears to be enhanced by using VR technology [5–7]. Although most of these studies still consist of small experiments without randomized control trials , they demonstrate the feasibility of the application of VR technology in this clinical field.
In regard to standing balance, systems based on force platforms are particularly interesting, since they enable to estimate the weight distribution of the patients by means of pressure sensors [9, 10]. These devices are expensive and require a dedicated area in the clinical facilities due to their size, weight and set-up. In this respect, computerized dynamic posturography can assess the ability of the automatic motor system to quickly recover from an unexpected external disturbance. Some of these systems even offer interactive and functional training exercises that fit the patients' conditions. In comparison with these platforms, the Nintendo® WBB (a peripheral of the Nintendo® Wii gaming system) is an inexpensive interface (less than $100USD) that has widespread availability. The WBB also has the advantage of being portable, easy and comfortable to handle thanks to its small size (0.511 m. wide by 0.316 m. long by 0.053 m. thick) and weight (3.5 kg. without batteries). Furthermore, it is a device with Bluetooth wireless connectivity that is battery operated. The WBB contains four force sensors (located in each corner) that are used to measure the user's center of balance and weight. Following the Nintendo® gaming philosophy, users can interact naturally with the game (by means of weight transferences).
The number of studies that include Nintendo® Wii or WBB in the rehabilitation process is increasing but still limited. Saposnik et al. evaluated the feasibility, safety and efficacy of VR rehabilitation using the Nintendo® Wii gaming system with entertainment software to improve arm motor recovery in stroke patients . Since the study is focused on improving arm recovery, the WBB was not used. Deutch et al. also use commercial software (Wii sports) to describe the feasibility and clinical efficacy of Nintendo® Wii to augment the rehabilitation of an adolescent with cerebral palsy . Loh et al. use this system as well and reported improvement in a group of patients with stroke in a non-controlled study . Sugarman et al. report the feasibility and outcome of the WBB with a commercial program for balance training after stroke . Although this software is not designed for balance recovery after stroke, they highlight its potential to be used in clinical settings in order to improve balance. In this sense, Clark et al.  demonstrated the convergent validity and the clinical utility of the WBB compared to a laboratory-grade force platform, which is considered the gold standard measure of balance. The results suggest that the WBB could be considered as a valid portable low-cost tool for assessing standing balance. However, the Nintendo® Wii and WBB are entertainment systems oriented to healthy people that offer a gaming experience that differs from the therapy required by patients with ABI [16, 17]. This fact has encouraged different authors to develop custom made applications oriented to diminished people using the WBB [18–22]. However, they are still very conceptual designs or lack more powerful studies to evaluate their efficacy.
Therefore, we designed eBaViR, a virtual rehabilitation system for balance recovery that provides motivational task oriented exercises specifically designed for ABI people by clinical therapists. The system can fit the patients' impairment to provide a particular training session, allowing the therapists to customize the duration and difficulty of exercises to the needs of the patients in each session.
The aim of this study is to evaluate the efficacy of the eBaViR system as a rehabilitation tool for balance recovery. In this contribution, we present a randomized and controlled single blinded trial to evaluate the influence of eBaViR on balance rehabilitation of ABI patients. We hypothesize that eBaViR is feasible, safe and potentially efficacious in enhancing standing balance.