Repeated exposure to virtual reality decreases reliance on visual inputs for balance control in healthy adults.

Postural control may encounter acute challenges when individuals are immersed in a virtual reality (VR) environment, making VR a potential pertinent tool for enhancing balance capacity. Nonetheless, the effects of repeated exposure to VR on balance control remain to be fully elucidated. Fifty-five healthy participants stood upright for six bouts of 90 s each in an immersive virtual reality (VR) environment using a head-mounted display (repeated VR exposure). During these bouts, participants experienced simulated forward and backward displacements. Before and after the repeated VR exposure, the center of pressure mean velocity (VELCOP) was measured in response to simulated forward and backward displacement in VR, as well as during quiet upright standing with eyes open (EO) and closed (EC) in the real environment. The results revealed a significant decrease in VELCOP for forward and backward simulated displacements in both antero-posterior and medio-lateral directions (p < 0.01) after compared to before repeated VR exposure. Furthermore, VELCOP significantly decreased when participants stood upright in EC (-5%; p = 0.004), but not EO (+3%; p > 0.05) in the real environment after repeated VR exposure. The Romberg ratio (EC/EO) was reduced in both antero-posterior and medio-lateral directions (p < 0.05) after VR exposure. This study indicates that repeated exposure to VR induces changes in balance control in both virtual and real environments. These changes may be attributed, in part, to a reduction in the weighting of visual inputs in the multisensory integration process occurring during upright standing. Accordingly, these findings highlight VR as a potentially effective tool for balance rehabilitation. SIGNIFICANCE STATEMENT: This study indicates that repeated exposure to VR induces changes in balance control in both virtual and real environments that can rely, in part, on a reduction in the weighting of visual inputs in the multisensory integration process occurring during upright standing.

Characterizing biased visuospatial perception in complex regional pain syndrome.

BACKGROUND: Patients suffering from complex regional pain syndrome (CRPS) are increasingly shown to be affected by cognitive difficulties. While these cognitive symptoms were initially described as limited to the perception, representation and use of the body, that is, the somatic space, they were recently shown to also extend to the perception of extra-somatic space. CRPS patients seem indeed to pay less attention to visual stimuli occurring in the same side of space as their affected limb and especially those occurring close to that limb. The aim of the present study was to more precisely characterize these visuospatial biases, by investigating whether they may be dependent on the visually perceived proximity between the visual stimuli and the affected limb. METHODS: Upper-limb CRPS patients and matched control participants performed temporal order judgements on visual stimuli, one presented in either side of space, while they could either see their hands near the visual stimuli or not. RESULTS: Visuospatial biases were not modulated by the availability of visual feedback about the hands. However, secondary analyses revealed that these biases depended on the type of rehabilitation program that the patients followed: whereas patients who did not follow any specific program presented significant biases to the detriment of visual stimuli in the affected side of space, patients who did follow a CRPS-specialized program did not. CONCLUSIONS: Patients' cognitive strategies will be important to consider when studying inter-individual differences in the cognitive symptomatology and associated cognitive-based rehabilitation procedures in CRPS. SIGNIFICANCE: The existence of biases in visuospatial perception in Complex Regional Pain Syndrome has been reported but not always systematically replicated. We show that these biases might depend on the type of general rehabilitation program that the patients follow. Patients' individual cognitive strategies will be important to consider when studying the cognitive symptomatology of CRPS.

The long-term effect of complex regional pain syndrome type 1 on disability and quality of life after foot injury.

PURPOSE: To study the long-term evolution of patients with lower-limb Complex Regional Pain Syndrome (CRPS), focusing on functional and proprioceptive aspects and quality of life. METHODS: In 20 patients suffering from chronic distal lower-limb CRPS diagnosed using Budapest criteria, we assessed joint position sense and strength of the knee muscles at the CRPS and unaffected leg, functional exercise capacity, pain, CRPS severity score, quality of life and kinesiophobia. Similar assessments were performed in 20 age-matched controls. RESULTS: The joint position performance (at 45°) was significantly lower for the CRPS leg as compared to controls. The knee extensor strength of the CRPS leg was significantly reduced as compared to the unaffected leg (-27%) and controls (-42%). CRPS patients showed significantly reduced performance at the 6 min-walk test as compared to their age group predicted value and controls. Patients suffering from CRPS for 3.8 years in average still exhibit high pain, severity and kinesiophobia scores. CONCLUSIONS: Long-term deficits in strength and proprioceptive impairments are observed at the knee joint of the CRPS leg. This persistent functional disability has significant repercussions on the quality of life. We highlight the importance of including strength and proprioceptive exercises in the therapeutic approaches for CPRS patients.IMPLICATIONS FOR REHABILITATIONThe long-term evolution of patients suffering from lower-limb Complex Regional Pain Syndrome is associated with persistent disability, pain and impacts the quality of life.Strength, proprioceptive, functional and subjective assessments are necessary to better identify deficits.Rehabilitation should focus on the overall deficit of the affected and contralateral limb.

Visuomotor impairments in complex regional pain syndrome during pointing tasks.

ABSTRACT: Complex regional pain syndrome (CRPS) is thought to be characterized by cognitive deficits affecting patients' ability to represent, perceive, and use their affected limb as well as its surrounding space. This has been tested, among others, by straight-ahead tasks testing oneself's egocentric representation, but such experiments lead to inconsistent results. Because spatial cognitive abilities encompass various processes, we completed such evaluations by varying the sensory inputs used to perform the task. Complex regional pain syndrome and matched control participants were asked to assess their own body midline either visually (ie, by means of a moving visual cue) or manually (ie, by straight-ahead pointing with one of their upper limbs) and to reach and point to visual targets at different spatial locations. Although the 2 former tasks only required one single sensory input to be performed (ie, either visual or proprioceptive), the latter task was based on the ability to coordinate perception of the position of one's own limb with visuospatial perception. However, in this latter task, limb position could only be estimated by proprioception, as vision of the limb was prevented. Whereas in the 2 former tasks CRPS participants' performance was not different from that of controls, they made significantly more deviations errors during the visuospatial task, regardless of the limb used to point or the direction of pointing. Results suggest that CRPS patients are not specifically characterized by difficulties in representing their body but, more particularly, in integrating somatic information (ie, proprioception) during visually guided movements of the limb.

Robot-assisted line bisection in patients with Complex Regional Pain Syndrome.

Complex Regional Pain Syndrome (CRPS) is characterized by pain, motor and inflammatory symptoms usually affecting one limb. Cognitive difficulties have been reported to affect patients' ability to represent, perceive and use their affected limb. It is debated whether these difficulties result from deficits in controlling goal-directed movements in space or from a learned strategy to protect the affected limb. In order to dissociate the two hypotheses, patients with upper-limb CRPS were asked to move with their unaffected hand towards visual targets projected at different positions on a horizontal semi-reflexive mirror. By means of a robotic handle placed below the screen, they were asked to move a cursor, to reach and cross lines at their estimated midpoint. In some of the stimulation series, the affected hand was placed below the mirror so that some lines appeared projected onto that hand. Vision of the hands and the robotic handle was preserved or prevented by opening or closing a shutter below the mirror. Lines were displayed on the mirror according to which part of the body was affected (ispi- vs. contralateral) and the actual position of the affected hand (inside vs. outside the workspace). Comparatively to control participants, CRPS patients generally biased their estimation by bisecting the lines towards their left side, irrelative of which part of the body was affected and the position of the affected hand, both in ipsi- and contralateral space, with only a few exceptions. Our results are in line with previous studies having described a visuospatial deficit in CRPS patients and discard the explanation of observed symptoms in terms of learned nonuse strategies, as only the unaffected hand was used to perform the task. It is suggested that CRPS patients can display difficulties to perform tasks requesting visuo-motor coordination, reflecting the complex cortical reorganization occurring in CRPS.

Biased visuospatial perception in complex regional pain syndrome.

Complex regional pain syndrome (CRPS) is a chronic pain condition associating sensory, motor, trophic and autonomic symptoms in one limb. Cognitive difficulties have also been reported, affecting the patients' ability to mentally represent, perceive and use their affected limb. However, the nature of these deficits is still a matter of debate. Recent studies suggest that cognitive deficits are limited to body-related information and body perception, while not extending to external space. Here we challenge that statement, by using temporal order judgment (TOJ) tasks with tactile (i.e. body) or visual (i.e. extra-body) stimuli in patients with upper-limb CRPS. TOJ tasks allow characterizing cognitive biases to the advantage of one of the two sides of space. While the tactile TOJ tasks did not show any significant results, significant cognitive biases were observed in the visual TOJ tasks, affecting mostly the perception of visual stimuli occurring in the immediate vicinity of the affected limb. Our results clearly demonstrate the presence of visuospatial deficits in CRPS, corroborating the cortical contribution to the CRPS pathophysiology, and supporting the utility of developing rehabilitation techniques modifying visuospatial abilities to treat chronic pain.

3D augmented reality mirror visual feedback therapy applied to the treatment of persistent, unilateral upper extremity neuropathic pain: a preliminary study.

Objective: We assessed whether or not pain relief could be achieved with a new system that combines 3D augmented reality system (3DARS) and the principles of mirror visual feedback. Methods: Twenty-two patients between 18 and 75 years of age who suffered of chronic neuropathic pain. Each patient performed five 3DARS sessions treatment of 20 mins spread over a period of one week. The following pain parameters were assessed: (1) visual analogic scale after each treatment session (2) McGill pain scale and DN4 questionnaire were completed before the first session and 24 h after the last session. Results: The mean improvement of VAS per session was 29% (p < 0.001). There was an immediate session effect demonstrating a systematic improvement in pain between the beginning and the end of each session. We noted that this pain reduction was partially preserved until the next session. If we compare the pain level at baseline and 24 h after the last session, there was a significant decrease (p < 0.001) of pain of 37%. There was a significant decrease (p < 0.001) on the McGill Pain Questionnaire and DN4 questionnaire (p < 0.01). Conclusion: Our results indicate that 3DARS induced a significant pain decrease for patients who presented chronic neuropathic pain in a unilateral upper extremity. While further research is necessary before definitive conclusions can be drawn, clinicians could implement the approach as a preparatory adjunct for providing temporary pain relief aimed at enhancing chronic pain patients' tolerance of manual therapy and exercise intervention. Level of Evidence: 4.

Objective evaluation of elbow flexion strength and fatigability after nerve transfer in adult traumatic upper brachial plexus injuries.

Nerve transfers Oberlin-type are currently used in upper brachial plexus lesions to recover elbow flexion. Is the regained active motion sufficient to resume heavy manual activities? Five adult patients (mean age 37 years) operated of a nerve transfer to recover elbow flexion (transfer of a motor fascicle of the ulnar nerve to the motor branch of the biceps; in three patients, additional transfer from the median to the motor nerve of the brachialis) were clinically and isokinetically evaluated, after a mean follow-up of 47 months. The median Constant-Murley score was 22/100, the DASH 56/100 and the MEPI 60/100. For isokinetic tests the most significant finding was a severe deficit of elbow strength, of about 80%. No patient was able to maintain an isometric contraction during sufficient time to evaluate fatigability. This preliminary study suggests that major functional impairments persist despite early recovery of elbow flexion. These results should be confirmed in a study on a larger group of patients.

Functional and outcome evaluation of the hand and wrist.

The first evaluation of the upper extremity and hand, performed by the surgeon at the outpatient clinic, is fundamental to understanding the patient's problem, determining the best treatment options, and, in the case of a surgical indication, assessing the preoperative status. In addition to recording the patient's symptoms and complaints, the surgeon evaluates anatomic integrity, stability, mobility, trophicity, strength, and sensibility. In many patients, especially patients with severe handicaps or those who anticipate long delays in rehabilitation, in litigation problems, or as part of prospective clinical research, this classic evaluation is not sufficient. The authors recommend that to accommodate these patients, a laboratory of functional evaluation of the hand should be established. The evaluation, performed by independent reviewers, ideally includes techniques allowing objective measurements of kinematics, strength, sensibility, and global hand function and dexterity. Pain assessment using the VAS is indispensable. The results may be presented as scores based on to the patient's problem. The researchers should analyze precisely how the scores were constructed. Questionnaires are part of the evaluation armamentarium. As with other tools, questionnaires allow us to understand better what our patients experience. They do not replace physical examination. Questionnaires also could be used for routine screening in a general upper limb practice, even before the patient sees the hand surgeon. The choice of the questionnaire is important; the reviewer should make sure that the patient understands all questions, that the questions are not redundant, and that they do apply to the patient. Generic health status instruments such as the SF-36 allow comparison across a variety of health problems, including mental and physical conditions, but are not sensitive to upper extremity disability. The DASH questionnaire seems a better choice, allowing a standardized outcome evaluation. Dedicated questionnaires have been developed for specific conditions (eg, carpal tunnel syndrome). As discussed by Amadio, questionnaires are easier to perform than physical testing, can be self-administered, and require no special equipment, saving the cost of an examiner, avoiding the complexities of scheduling a follow-up examination, and eliminating the possibility of observer bias. The patient is less likely to offer polite but incorrect responses. Questionnaires are especially useful when patient's perceptions are important to assess. Questionnaires also could be used in longitudinal studies to assess improvement or aggravation. The use of questionnaires is therefore especially indicated in studies involving a large number of patients, when observer bias and costs are concerns, and when the main outcome measurements are satisfaction, symptoms, or functional status. Amadio has pointed out that questionnaires are not the best tool to measure anatomic or physiologic impairments.