Unilateral spatial neglect (USN) is a common and highly disabling condition following acquired brain injury (ABI), significantly impairing individuals' ability to perform daily activities and reducing their autonomy. It frequently affects patients who have suffered a stroke or traumatic brain injury, and it is often associated with worse functional outcomes and increased care needs. Despite advances in neurorehabilitation, conventional assessment and treatment tools for USN have shown limitations in sensitivity and ecological validity.

Immersive Functional Virtual Reality (IFVR) is an emerging and promising technology that creates controlled, interactive environments, facilitating both assessment and rehabilitation in a motivating and safe way. The REVINE study explores the feasibility, usability, and preliminary clinical effects of an immersive VR-based intervention tailored to address motor and spatial deficits in adults with ABI and USN.

This is a prospective, non-controlled feasibility study using a single-group interrupted time series design. Participants (N=30) will be recruited from two neurorehabilitation services in Catalonia (Spain): the Neurological Rehabilitation and Brain Injury Unit at Vall d'Hebron University Hospital and the Outpatient Rehabilitation Service at Consorci Hospitalari de Vic. Eligible participants will be adults with ABI in the subacute or chronic phase, presenting USN (as measured by the Catherine Bergego Scale and the Bells Cancellation Test) and mild-to-moderate upper limb impairment.

The intervention consists of 12 supervised individual IFVR sessions (30 minutes/session, 3 times/week for 4 weeks), using the KINESIX system (NeuroGroup XR Inc., Montreal, Canada). A progressive series of gamified tasks will be delivered through immersive VR, targeting spatial exploration and upper limb function, with adjustable difficulty and real-time feedback.

Participants will undergo three pre-intervention and three post-intervention evaluations, spaced one month apart. Clinical outcomes include the degree of USN (measured by the Catherine Bergego Scale, the Bells Cancellation Test, and the KINESIX light-reaching test), usability (System Usability Scale), and satisfaction (User Satisfaction Evaluation Questionnaire). Feasibility outcomes include recruitment and retention rates, adherence to treatment, session completion times, adverse events, and therapist assistance level.

We hypothesize that IFVR will be a viable and well-accepted intervention, with high user satisfaction, minimal adverse effects, and measurable improvements in neglect-related outcomes. This study aims to inform the future design of larger-scale trials and support the integration of IFVR into routine neurorehabilitation settings or home-based telerehabilitation programs.

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.

Inclusion Criteria:

• Age 18 years or older.
• Diagnosis of acquired brain injury (stroke or traumatic brain injury) in the subacute phase (>7 days to 6 months) or chronic phase (>6 months).
• Presence of unilateral spatial neglect, defined as omission of 6 or more bells on the left hemifield in the Bells Cancellation Test.
• Currently receiving care at the Outpatient Rehabilitation Service of the Consorci Hospitalari de Vic or at Vall d'Hebron University Hospital, or listed in the historical patient registry of these centers.
• Presence of mild to moderate upper limb impairment, defined as a score >29 on the Fugl-Meyer Upper-Extremity scale.
• Medically stable and eligible to begin a rehabilitation program.
• Willing to participate in the study and able to provide signed informed consent.

Exclusion Criteria:

• Delirium and/or behavioral disturbances that prevent the participant from following simple instructions.
• Severe cognitive impairment, defined as a Mini-Mental State Examination (MMSE) score below 18, that interferes with the use of virtual reality.
• Severe visual and/or auditory impairment that prevents the use of immersive VR goggles.
• Severe language comprehension difficulties that interfere with the instructions during the intervention.
• Hypersensitivity that prevents the placement of the VR headset.
• Headache or dizziness induced by the use of VR goggles.
• History of photosensitive epilepsy.

Individual participant data (IPD) will not be shared due to the exploratory nature of this feasibility study and the limited sample size. Additionally, the study involves sensitive health data from individuals with acquired brain injury, and the data use has been approved only for internal analysis within the research team under strict confidentiality agreements. No extended consent for data sharing beyond the current project scope has been obtained.