Personalized Adaptive Mirror Therapy for Upper-Limb Post-Stroke Rehabilitation Using Virtual Reality and Myoelectric Control: VVITAstroke Pilot RCT

BACKGROUND. Cerebral stroke is one of the main causes of disability in adults and involves, in the most common case, a hemiparesis of the contralateral upper limb. This motor deficit, which occurs for 80% of patients in the acute phase and 40% in the chronic phase, can be improved through the involvement of patients in appropriate rehabilitation with increased intensity and task-specificity. Technological advances in recent years have provided new methodologies to support and promote the rehabilitation process by increasing its repeatability and intensity. In particular, rehabilitation systems integrated into virtual reality environments (VR, Virtual Reality) can provide more complex work scenarios than rehabilitation systems and, thanks to the immersiveness of the systems with a visor integrated into a helmet wearable, it is possible to simulate activities of daily life, thus effectively increasing the active participation and motivation of the patient in carrying out and completing the rehabilitation path. Further recent methodological advances have allowed the development of approaches to personalized rehabilitation programs, aimed at restoring the specific components of the control motor deficits. In particular, it has been noted that deficits in motor function that accompany patients in stroke outcomes are characterized by specific patterns of muscle activation or pathological muscle synergies. In this regard, recently quantitative approaches have been developed for the identification of motor coordination in healthy subjects that relies on the decomposition of patterns of muscle activation as a combination of physiological muscle synergies through factorization algorithms. These approaches of decomposition have highlighted the changes induced in the coordination of muscle following stroke. Hence, the characterization of the alterations of activation patterns post-stroke muscle by decomposition in combination of muscle synergies can provide an indicator of the pathological state, with prognostic value on recovery induced by a therapeutic intervention and more accurate than current clinical scales and quantitative measurements based on purely kinematic measurements. In addition to the applications of muscle synergies to rehabilitation. In recent years, the use of myoelectric interfaces for the control of actuators such as exoskeletons or prostheses has become increasingly widespread. Myoelectric interfaces can decode the patient's intention through the residual myoelectric activity of the paretic limb allowing the execution of voluntary movements through their normal cortico-spinal pathway, thus providing them with feedback (e.g. visual) and effectively establishing a closed-loop system that promotes learning and fostering active participation, increasing coordination muscle strength and reducing spasticity. Myoelectric interfaces for rehabilitation also aim to activate neuroplasticity mechanisms that reshape neuromuscular activity and lead to motor learning and in some cases, to the restoration of motor function.

AIM AND DESIGN OF THE STUDY. The aim of the present pilot study is therefore to evaluate the effectiveness of a protocol for the upper limb post-stroke rehabilitation through a Virtual Reality system embedded with myoelectric control. All the devices used in this study such as for the visualization of environments virtual (HTC-Vive) and for recording electromyographic signals (Myo Armband) are available on the consumer electronics market and have been previously used in other clinical study involving humans. Study Design is a pilot Randomized Controlled Trial.

PARTICIPANTS. We enrolled patients who had experienced stroke more than a year before the time of the first evaluation were enrolled for this study.

Criteria for enrolment were: 1) upper limb deficits with sufficient level of muscle power, so that movement is possible with gravity eliminated (F=2), or muscle movement is possible against gravity (F=3), as assessed with Medical Research Council (MRC) scale grades not below 1; 2) at least 18 but not more than 54 out of 66, respectively 27% and 80% of the upper limb functionality, as assessed with the Upper Limb Extremity section of the Fugl-Meyer Assessment (FMA) scale; 3) absence of severe linguistic impairments which may limit the understanding of the instructions; 4) absence of cognitive impairments, assessed with the Addenbrooke's Cognitive Examination - Revised version for Italian population, visual deficit or other neurologic disease in comorbidity, which may affect the patient's ability to interact with the VR environment.

Since age-related and severity-related differences were found in motor outcomes following VR upper limb treatments, we created a blocked randomization list with two levels of stratification (age and severity), which guaranteed a balanced within-group split throughout the data collection process. Therefore, participants aged between 18 and 55 years old were considered as young participants according to previous studies, while those aged between 56 and 80 years were considered as older. The level of impairment was computed based on two cut-offs obtained through the administration of the FMA-UE scale. We considered patients with severe impairment, whose scores fell between 18 and 36, namely, those with 27-54% motor proficiency. On the other hand, scores ranging from 37 to 54 (56-80%) were considered moderate impairment. We used the sealed envelope tool to create the randomization list of participants as a function of the stratification number of randomization blocks (age, level of impairment), which revealed the need to enrol at least 12 patients. This sample size was also used in previous work about the effectiveness of the VR system on the rehabilitation of the upper limb in stroke patients.