Immersive Functional Virtual Reality in People With Acquired Brain Injury and Unilateral Spatial Neglect

Background and Rationale

Acquired brain injury (ABI), including stroke and traumatic brain injury, is a leading cause of long-term disability worldwide. One of its most disabling consequences is unilateral spatial neglect (USN), a complex perceptual-attentional syndrome characterized by an impaired ability to attend, respond, or orient to stimuli presented on the side opposite the brain lesion. USN significantly affects functional independence and daily living activities such as grooming, eating, dressing, or mobility, and it is associated with a poorer rehabilitation prognosis and prolonged dependence on caregivers.

Despite the high prevalence and impact of USN, conventional assessment tools (e.g., cancellation tasks, line bisection) often lack sensitivity to detect subtle deficits and do not reflect real-life performance. Furthermore, traditional rehabilitation approaches may be insufficient to address the multifaceted nature of USN, especially its extrapersonal and representational aspects.

Virtual reality (VR) technologies provide controlled, interactive environments that simulate real-life situations, enabling both the assessment and treatment of cognitive and motor impairments. Immersive Functional Virtual Reality (IFVR), in particular, can engage users in multisensory, gamified tasks that promote neuroplasticity while ensuring ecological validity. Previous evidence supports the use of VR-especially semi-immersive systems-for USN rehabilitation, though immersive systems remain underexplored in clinical trials and feasibility studies.

Study Objectives

The REVINE project aims to evaluate the feasibility, usability, and preliminary clinical effects of an IFVR intervention in adults with ABI and USN.

The general objectives of the REVINE project are:

• GO1. To describe the feasibility of using immersive functional virtual reality (IFVR) for the rehabilitation of individuals with unilateral spatial neglect (USN) following acquired brain injury (ABI).
• GO2. To describe the usability of IFVR among individuals with USN after ABI.
• GO3. To evaluate the applicability of IFVR as an assessment tool for USN in individuals with ABI.
• GO4. To assess the clinical effects of IFVR on USN in people with ABI.

The specific objectives are:

• SO1. To describe recruitment and consent rates, as well as participant retention throughout the study.
• SO2. To record treatment adherence based on the number of sessions attended versus those planned.
• SO3. To quantify the time spent during intervention and assessment sessions.
• SO4. To record the type, severity, and duration of potential adverse events during treatment.
• SO5. To document the time spent according to the type of game used and its level of difficulty.
• SO6. To analyse the level of therapist assistance required during intervention sessions.
• SO7. To determine perceived usability using the System Usability Scale (SUS).
• SO8. To describe user satisfaction with the IFVR intervention using the User Satisfaction Evaluation Questionnaire (USEQ).
• SO9. To evaluate the clinical effect of IFVR on USN severity using the Bells Cancellation test, the Catherine Bergego Scale (CBS), and the KINESIX light test.

Study Design

This is a prospective, single-arm feasibility study employing a single interrupted time series design. A total of 30 participants will be recruited using a non-probabilistic convenience sampling method. Each participant will undergo three pre-intervention evaluations (T1, T2, T3) and three post-intervention evaluations (T4, T5, T6), each spaced one month apart. The intervention will consist of 12 individual, supervised IFVR sessions over four weeks (three sessions per week, 30 minutes per session).

Setting and Participants

The study will take place at two specialized rehabilitation centers in Catalonia, Spain:

• The Neurological Rehabilitation and Brain Injury Unit at Vall d'Hebron University Hospital (Barcelona).
• The Outpatient Rehabilitation Service of the Consorci Hospitalari de Vic (Vic, Barcelona).

Eligible participants must meet the following criteria:

• Adults (≥18 years) with a diagnosis of ABI in the subacute (>7 days to 6 months) or chronic phase (>6 months).
• Presence of USN (≥6 omissions in the Bells Cancellation Test).
• Mild to moderate upper limb impairment (Fugl-Meyer Upper Extremity >29).
• Medically stable and capable of participating in rehabilitation.

Exclusion criteria include severe cognitive, visual, or auditory deficits, language comprehension difficulties, hypersensitivity or intolerance to VR headsets, photosensitive epilepsy, or active behavioral disturbances.

Intervention

The IFVR intervention will be delivered using the KINESIX system (NeuroGroup XR Inc.), consisting of a VR headset with integrated software, a therapist tablet interface, and a web-based monitoring platform. The intervention includes 12 exercises grouped into three modules: practice, activities, and participation. Tasks will focus on visuospatial exploration, reaching, grasping, and manipulating virtual objects, particularly in the contralesional space.

Exercises are designed with five increasing difficulty levels to support motor learning and maintain user engagement. Playlists of exercises will progress in difficulty as the participant advances through sessions. Sessions will take place in a safe space under the supervision of a physiotherapist or occupational therapist.

Outcome Measures

Feasibility Outcomes:

• Recruitment, consent, and retention rates.
• Session adherence and duration.
• Frequency and severity of adverse events.
• Level of therapist assistance (7-point Likert scale).

Usability and Satisfaction:

• System Usability Scale (SUS): 10-item Likert scale, score range 0-100.
• User Satisfaction Evaluation Questionnaire (USEQ): 6-item Likert scale, average score 1-7.

Clinical Outcomes:

• Catherine Bergego Scale (CBS): Assesses functional neglect in daily activities (score 0-30).
• Bells Cancellation Test: Screening tool for visual neglect (≥6 omissions indicates USN).
• KINESIX Light Reach Test: Measures spatial reach using 209 LED lights to assess peripersonal and extrapersonal attention.

Safety Considerations

Initial familiarization with the VR headset will ensure gradual exposure to immersive environments. Any adverse events (e.g., dizziness, nausea) will be documented and managed using a pre-defined protocol. Sessions may be interrupted or modified based on participant tolerance. All devices will be disinfected between uses.

Timeline

The study will span 24 months, starting in December 2024. Recruitment will begin in March 2025, following ethics approval, and continue for approximately 12 months. Post-intervention follow-up will conclude by late 2026. Data analysis is planned for November 2026 to January 2027.

Significance and Innovation

This study will provide essential insights into the practical implementation of immersive VR technologies in neurorehabilitation settings. By focusing on feasibility and user experience, the REVINE project seeks to bridge the gap between experimental innovation and clinical application. The findings will inform the design of future randomized controlled trials and the potential integration of IFVR into conventional and remote rehabilitation programs.