Clinical effectiveness of immersive virtual reality in medical rehabilitation: results, limitations and prospects

Introduction

Immersive virtual reality is an emerging technology that is generating increasing interest in the research community due to its wide range of applications, particularly in the cognitive-motor domain. This innovative approach involves human-computer interaction in augmented or immersive virtual reality, allowing users to respond realistically to virtual stimuli [1]. Recent advances and the development of cutting-edge technologies have significantly contributed to progress in physical rehabilitation. These innovations offer new approaches to motor function recovery and represent valuable assessment tools capable of determining outcomes with high accuracy and objectivity [1, 2]. A key feature of virtual reality (VR) is the creation of an immersive environment that simulates both everyday and unusual activities through multisensory stimulation in a safe and controlled setting. This quality of immersion enhances patient engagement and is often perceived as motivating and entertaining. Furthermore, the VR environment can be tailored to the residual capabilities of individual users [3].

Proprioception provides the central nervous system with real-time information about biomechanical parameters such as speed, force, direction, and acceleration, as well as physiological changes in muscles, tendons, and joints. However, visual illusions can alter proprioceptive perception. In rehabilitation, such illusions are often used to improve therapeutic outcomes. For example, Burden et al. used IVR to manipulate visual feedback regarding hand position, thereby improving motor function [3]. The sense of embodiment in IVR arises when individuals observe a virtual body that closely resembles their own, with realism and a first-person perspective being critical factors for the emergence of a sense of ownership over the virtual body [4].

Over the past few decades, various tools have been developed to improve upper limb rehabilitation [5]. Among these, VR has proven valuable due to its ability to provide real-time feedback through sensors, thereby enhancing both motor skills and learning. It also positively affects patient motivation [1]. Moreover, VR-based interventions are adaptable to different age groups and individual needs. Numerous studies have shown that IVR-based rehabilitation sessions are perceived as less painful, more enjoyable, and more engaging compared to traditional therapies. This increased engagement helps reduce perceived discomfort and boredom during therapy [6, 7].

Virtual reality is used in the rehabilitation of a wide range of motor impairments, especially those resulting from neurological diseases such as Parkinson's disease (PD), multiple sclerosis (MS), cerebral palsy, and stroke. Studies using this technology have shown significant functional improvements in both preventing deterioration and promoting recovery. As global life expectancy increases, the public health burden of neurological disorders continues to grow. In 2016, motor impairments represented one of the leading causes of increased disability-adjusted life years, with upper limb dysfunction being particularly prominent [9]. Although VR is increasingly being studied as a training method in neurological rehabilitation, most research has focused on stroke recovery, with relatively little data available for PD, amputations, and pain-related conditions. Moreover, the majority of studies focus on adult populations [10].

Acute/Subacute Stroke

Stroke is a neurological condition characterized by the death of neurons in specific brain regions due to disrupted blood flow and subsequent oxygen deprivation. Symptoms appear rapidly and may include paralysis, sensory disturbances, spasticity, facial asymmetry, speech and comprehension difficulties, headaches, balance and vision disorders, impaired coordination, and loss of consciousness [8]. Approximately 80% of stroke survivors experience upper limb dysfunction, yet only one-third regain satisfactory hand function in the chronic recovery phase, only 26% resume their daily activities independently, and only 26% of those will be able to perform daily activities again [10]. Stroke remains the leading cause of long-term disability in adults and the second leading cause of dementia worldwide. This, in turn, places a substantial economic burden on healthcare systems and society as a whole, contributing to the failure of neurorehabilitation goals [11]. The implementation of new technologies is urgently needed to facilitate skill recovery, reduce rehabilitation costs, increase accessibility, and decrease the number of therapists required per session. In this context, virtual reality represents a promising solution for telerehabilitation [8].

Developing upper limb training protocols using new technologies such as IVR is essential to support functional recovery. These protocols should be based on motor learning principles and have the potential to improve motor skills by promoting neuroplasticity [1]. Studies have shown that supplementing traditional therapy with one additional hour of IVR training leads to greater improvement in motor function of the affected limb and induces cortical changes compared to standard physiotherapy [12]. Another study confirmed that mirrored limb training using IVR promotes neuroplasticity, leading to improved motor function of the affected limb. Park W. and colleagues (Korea) analyzed improvements in ideomotor apraxia in a post-stroke patient. After 12 weeks of IVR training, the patient showed improvement in almost all symptoms. These findings suggest that IVR may be an effective tool for the rehabilitation of ideomotor apraxia [13]. The main identified limitations include small sample sizes, short intervention periods, and the limited volume of available literature for review.

IVR has been shown to effectively improve symptoms of ideomotor apraxia [13], induce positive changes in inflammation levels, oxidative stress, and serum BDNF biomarkers, as well as increase functional assessment scores in individuals with chronic stroke [14]. IVR appears particularly useful for individuals with mild to moderate upper limb impairments.

However, the reviewed studies have several limitations, including small sample sizes, which may affect the generalizability of the results. Additionally, variability in the control of standard therapy protocols across different patient groups introduces potential bias into the results.

Large-scale, well-designed studies are necessary to strengthen the evidence base and confirm these findings.

Chronic Stroke

In individuals with chronic stroke (chronic cerebral ischemia), motor impairments of the upper limbs persist in most cases, significantly limiting the ability to perform daily activities. The effectiveness of IVR in improving motor skills in this patient group has shown mixed results [11]. Weber L.M. (USA) states that the improvements in motor activity observed in his study did not reach statistical significance, likely due to the small sample size, the severity of impairments in the study population, and possibly insufficient treatment intensity [15]. A larger study might yield statistically significant results. In contrast, the study by Erhardsson, despite a smaller sample size, showed that all participants demonstrated improved upper limb activity ability, regardless of the severity of their impairments. Those who received the highest training dose showed progress on several outcome measures. Furthermore, according to Mallik A. et al. (Canada), these patients showed fewer improvements compared to healthy control groups [16].

Interactive voice communication is used to assist in reaching objects while avoiding obstacles, both in single-task and dual-task situations. A study comparing 13 individuals with mild stroke to 11 healthy control subjects showed that the stroke patient group performed worse in both task performance and speed. The study also revealed a link between confidence in hand abilities and task success. IVR can enhance confidence through graded difficulty levels and reward systems. Moreover, the inclusion of real-life scenarios may further increase patient confidence in using the affected limb in daily life [1].

Weber and colleagues applied mirroring strategies in IVR to 10 patients with chronic stroke and upper limb hemiparesis [15]. The intervention consisted of 12 sessions, each lasting 30 minutes. Unlike the study by Mekbib (China), improvements in motor function measured by the Fugl-Meyer Assessment for Upper Extremities (FMA-UE) and the Action Research Arm Test (ARAT) were not statistically significant [12]. Key limiting factors were the small sample size and the severity of impairments. Another important factor was the insufficient training intensity, which needed to be higher due to the low neuroplasticity observed in patients in the chronic phase of stroke. Compared to traditional physiotherapy, no significant difference in limb improvement was observed, although patients with less severe impairments showed better results [16, 17]. Huang and colleagues (China) demonstrated more substantial changes in serum inflammatory, oxidative stress, and neurotrophic biomarkers in the IVR group compared to the occupational therapy group. In line with previous studies, the IVR group also showed more significant improvements in upper limb functional assessment and active range of motion. Longer-term studies are needed to further analyze the impact of IVR on serum biomarkers in the chronic phase, as well as larger samples to better identify suitable candidates for this type of training [17]. According to Schuster-Amft and colleagues (Switzerland), IVR training offers numerous benefits and positive effects for upper limb motor recovery compared to traditional training [18]. This study evaluated individuals with chronic stroke (at least six months post-stroke) with mild to severe upper limb motor impairments. Although no significant differences were found between groups, the most notable improvements were observed during the first two weeks, after which progress stabilized until the final assessment. One advantage of IVR is the ability to customize characteristics and exercises individually. However, the study by Erhardsson et al. focused on commercially available, off-the-shelf systems for upper limb motor recovery in patients with chronic stroke. While these systems are inexpensive and attractive, they lack the flexibility to adapt to individual needs. Participants in this study could choose two games from five available options and select the duration of each session. The study showed that the optimal training time for significant improvement in upper limb condition is 900 minutes (at least 30 minutes, three times a week for 10 weeks). Although IVR technology appears promising, some limitations remain, including small sample sizes [15, 17], a lack of previous research, and suitability only for patients with mild stroke [18]. Moreover, the availability of an IVR training expert is necessary. Therefore, IVR plays a significant role in functional recovery after stroke [19]. It has demonstrated positive effects in both acute and chronic stages of stroke, promoting improvements in motor function, strength, dexterity, and range of motion [1, 11, 12], facilitating neuroplasticity and the ability to plan movement [14, 20].

A review by Holahan C. (UK) also emphasized that virtual reality protocols can offer new opportunities for post-stroke rehabilitation but also highlighted the need for larger-scale studies. IVR demonstrates similar effects across groups but with fewer compromises and better outcomes compared to traditional methods. The ARAT test shows that participants who undergo more training achieve better results. Some improvements, such as enhanced sensory function or upper limb muscle activity, were not statistically significant. IVR groups showed increased limb function, while the standard therapy group showed improvement in internal sensory function [21].

However, the reviewed studies have several methodological limitations, including small sample sizes and insufficient study duration to fully assess long-term effects (Table 1). Furthermore, the lack of previous studies including electroencephalogram (EEG) measurements presents another obstacle to fully understanding the collected data, and the constant presence of a rehabilitation specialist specializing in virtual reality games during all sessions may have influenced the results by introducing a control variable not reproduced in real-world settings [1].

Table 1. Results of the use of IVR in the rehabilitation of stroke patients

Notes: ↑ — increase; ↓ — decrease; = — unchanged; FMA-UE — upper extremity Fugl–Meyer assessment; Wrist AROM — active range of motion; WMFT — Wolf motor function test; BBS — Berg balance scale; TUGT — timed up and go test; SDMT — symbol digit modalities test; FMA-LE — Fugl-Meyer assessment lower extremity; MFT — manual function test; ARAT — action research arm test; BBT — box and block test; RPE — rating of perceived exertion; MMSE — mini-mental state examination; ul AST — upper limb apraxia score test.

IVR technology holds significant potential for the rehabilitation of patients with chronic stroke, offering innovative therapeutic approaches through deeper integration into treatment regimens, greater personalization of interventions, and broader application. As the cost of the technology decreases, it will become more accessible, enabling its use even in home settings. However, large-scale studies are needed to confirm its benefits and develop standardized protocols.

Parkinson's Disease

Parkinson's disease (PD) is a slowly progressive neurodegenerative disorder that primarily affects dopaminergic neurons in the substantia nigra [22]. PD is associated with a wide range of motor and non-motor symptoms. Non-motor symptoms include chronic pain, fatigue, sleep disturbances, as well as cognitive and emotional changes [23]. Motor manifestations typically include resting tremor, bradykinesia, rigidity, and balance and gait impairments. This affects both gross and fine motor skills, leading to reduced dexterity and difficulties in performing basic daily activities [22]. As there is currently no cure for PD, treatment focuses on symptom management and slowing disease progression. Physical activity plays a crucial role, especially in the early stages [8]. Virtual reality-based interventions have shown effectiveness in improving gait, balance, and overall mobility. Emerging research supports the feasibility, safety, and efficacy of IVR for people with PD [1].

Currently, the approach to treating Parkinson's disease is multidisciplinary, combining pharmacological and surgical interventions with physiotherapy and adapted physical activity [24]. The integration of IVR into traditional therapy has gained relevance in the cognitive and motor rehabilitation of patients with neurological disorders such as Parkinson's disease. This technological advancement has led to the development of the Virtual Reality Box and Block Test (VR-BBT), a reliable tool for measuring manual dexterity. Ona and colleagues demonstrated that VR-BBT can be used as a clinical assessment to measure upper limb manual dexterity in patients with early-stage Parkinson's disease [23]. Other studies have reported more significant improvements in upper limb movements, with patients also experiencing enjoyment and satisfaction [22] even compared to non-immersive virtual reality. However, IVR is also associated with a higher number of errors during performance and greater pressure to achieve good results compared to traditional methods [24]. Sanchez Herrera-Baeza et al. (Spain) showed more significant improvements in hand grip, fine coordination, and overall dexterity during rapid movements of the affected limb without any side effects. The Client Satisfaction Questionnaire (CSQ-8) showed high scores, reflecting 100% therapy adherence [22]. A limitation of these studies is the small sample size, as well as the need for an IVR expert and patient training in Parkinson's disease, as this technology is not suitable for every PD patient [1, 23].

In conclusion, IVR is a safe, effective, and feasible rehabilitation method for Parkinson's disease. It serves both as a therapeutic tool and a clinical test for measuring upper limb dexterity [22]. IVR sessions help improve hand grip, fine coordination, and gross motor skills [24]. Another review confirms these findings, acknowledging the potential of IVR in this area and highlighting its feasibility, usability, and safety, as well as promising benefits in combating common symptoms experienced by PD patients [25].

Interactive virtual reality proved to be more enjoyable and effective in managing time and tremor on the Unified Parkinson's Disease Rating Scale (UPDRS) compared to the group not using IVR, which made fewer errors. Both groups showed improvements on the BBT test. Significant progress was noted in strength, fine motor skills, overall coordination, and increased movement speed on the affected side [1]. Participants reported a high degree of satisfaction, despite the experience being a mental challenge.

Studies have identified some methodological limitations, including small sample sizes, which limit the generalizability of the results to the broader PD patient population. Additionally, fatigue required shorter breaks, which may have affected therapy effectiveness. The study focused only on patients with mild to moderate PD, excluding patients with more advanced forms of the disease. Finally, continuous professional monitoring was required throughout the study.

Amputation

Video games provide valuable support to traditional physiotherapy. Their engaging and enjoyable nature increases motivation for physical activity, replacing repetitive and monotonous exercises. The use of video games has been shown to have positive effects on motor, cognitive, and emotional domains [26]. The application of IVR in individuals with amputation has demonstrated benefits in muscle strength, limb prosthesis control, and self-perceived competence, with levels of engagement being high. During IVR sessions, participants reported low psychological pressure and tension [26, 27]. Research has also shown that visual feedback can modulate pain perception. Among various assistive devices, myoelectric prostheses are notable for enhancing the sense of control, while other devices, such as mirror therapy (MBT), rely on the reflected image of the intact limb. However, MBT has certain limitations that may reduce its effectiveness, and IVR can help mitigate them. A questionnaire assessing effectiveness showed that participants experienced a greater sense of control compared to standard methods [27]. Despite promising results, limitations such as small sample sizes and an insufficient number of studies on this topic need to be considered.

In individuals with amputation who used IVR alongside traditional therapy, outcomes similar to those observed in Parkinson's disease rehabilitation were achieved [1]. Furthermore, IVR was found to be effective in alleviating phantom limb pain [27]. While results are encouraging, most studies remain at the case series level, warranting caution when applying clinical recommendations [28].

All participants showed improvement in muscle strength and coordination. They also reported a high degree of satisfaction, including increased perceived competence, freedom of choice, and usefulness, while experiencing low levels of pressure and tension. Additionally, their control over the amputated limb improved, indicating potential benefits for neuromotor rehabilitation.

The study had several methodological limitations, including a small sample size and a lack of quantitative testing, undermining the reliability of the results. Furthermore, research on the topic of amputation and interactive virtual reality remains limited, with only two articles available, limiting the depth of analysis.

Fibromyalgia

Two out of three individuals with fibromyalgia syndrome (FMS) suffer from a condition known as kinesiophobia, characterized by a fear of physical exercise and movement. This condition can lead to avoidant behavior, especially in patients with maladaptive tendencies, and can also induce a nocebo effect [29]. The nocebo effect occurs when negative expectations from treatment lead to worse outcomes. Inactivity due to kinesiophobia leads to loss of muscle strength, endurance, mobility, and functionality, which in turn exacerbates mental health issues and pain symptoms [30, 31]. IVR has been shown to provide significant pain relief, particularly for chronic and acute pain conditions. Research suggests that pain relief is more substantial when using immersive virtual reality, which offers greater interactivity, resolution, and tracking accuracy [32]. According to Hullahn et al. (2019), IVR is beneficial for managing both pain and kinesiophobia, offering greater motivation compared to traditional physiotherapy [21]. A randomized study by Gülsen et al. (Turkey) confirmed the findings of Hullah, demonstrating similar reductions in pain and kinesiophobia using IVR without side effects [25]. A randomized study by Taka et al. also supports these findings, showing that IVR leads to improvements similar to traditional therapy but with additional psychological benefits and increased enjoyment [28]. A study by Darnall (2020) showed that IVR significantly reduces pain intensity, improves mood, sleep quality, and stress levels compared to audio-only devices [30]. Furthermore, Christensen et al. (2023) found that IVR increases pain threshold and reduces pain perception even in healthy individuals [32].

IVR has also shown promising results in the treatment of FMS, providing relief from persistent pain and distracting patients from discomfort [29, 30, 32]. It gradually helps restore functionality through movement, allowing patients to rediscover their abilities and potential [25, 28, 30].

The IVR system can be used remotely under the supervision of healthcare professionals, providing a convenient tool for home-based therapy.

Conclusion

IVR has demonstrated positive effects in individuals with issues resulting from stroke, Parkinson's disease, amputation, and pain conditions such as fibromyalgia syndrome. However, not all patient groups are suitable for this therapy, as outcomes are highly dependent on the severity of the condition and the presence of comorbidities. In the future, the development of guidelines for IVR-based physical rehabilitation protocols could significantly enhance the independence of people with disabilities and reduce chronic disability, thereby improving quality of life.

Interactive video therapy is promising as a tool for pain management through therapeutic games, especially when applied in home settings. It can improve movement perception, reduce pain intensity, and promote relaxation. When integrated with multidisciplinary treatment approaches, IVR can contribute to both motor function rehabilitation and mental health improvement. Further research is necessary to address the identified limitations and refine the use of IVR in clinical practice.