A hybrid brain-muscle-machine interface for stroke rehabilitation: Usability and functionality validation in a 2-week intensive intervention.

Introduction: The primary constraint of non-invasive brain-machine interfaces (BMIs) in stroke rehabilitation lies in the poor spatial resolution of motor intention related neural activity capture. To address this limitation, hybrid brain-muscle-machine interfaces (hBMIs) have been suggested as superior alternatives. These hybrid interfaces incorporate supplementary input data from muscle signals to enhance the accuracy, smoothness and dexterity of rehabilitation device control. Nevertheless, determining the distribution of control between the brain and muscles is a complex task, particularly when applied to exoskeletons with multiple degrees of freedom (DoFs). Here we present a feasibility, usability and functionality study of a bio-inspired hybrid brain-muscle machine interface to continuously control an upper limb exoskeleton with 7 DoFs. Methods: The system implements a hierarchical control strategy that follows the biologically natural motor command pathway from the brain to the muscles. Additionally, it employs an innovative mirror myoelectric decoder, offering patients a reference model to assist them in relearning healthy muscle activation patterns during training. Furthermore, the multi-DoF exoskeleton enables the practice of coordinated arm and hand movements, which may facilitate the early use of the affected arm in daily life activities. In this pilot trial six chronic and severely paralyzed patients controlled the multi-DoF exoskeleton using their brain and muscle activity. The intervention consisted of 2 weeks of hBMI training of functional tasks with the system followed by physiotherapy. Patients' feedback was collected during and after the trial by means of several feedback questionnaires. Assessment sessions comprised clinical scales and neurophysiological measurements, conducted prior to, immediately following the intervention, and at a 2-week follow-up. Results: Patients' feedback indicates a great adoption of the technology and their confidence in its rehabilitation potential. Half of the patients showed improvements in their arm function and 83% improved their hand function. Furthermore, we found improved patterns of muscle activation as well as increased motor evoked potentials after the intervention. Discussion: This underscores the significant potential of bio-inspired interfaces that engage the entire nervous system, spanning from the brain to the muscles, for the rehabilitation of stroke patients, even those who are severely paralyzed and in the chronic phase.

Functional synergy recruitment index as a reliable biomarker of motor function and recovery in chronic stroke patients.

Objective. Stroke affects the expression of muscle synergies underlying motor control, most notably in patients with poorer motor function. The majority of studies on muscle synergies have conventionally approached this analysis by assuming alterations in the inner structures of synergies after stroke. Although different synergy-based features based on this assumption have to some extent described pathological mechanisms in post-stroke neuromuscular control, a biomarker that reliably reflects motor function and recovery is still missing.Approach. Based on the theory of muscle synergies, we alternatively hypothesize that functional synergy structures are physically preserved and measure the temporal correlation between the recruitment profiles of healthy modules by paretic and healthy muscles, a feature hereafter reported as the FSRI. We measured clinical scores and extracted the muscle synergies of both ULs of 18 chronic stroke survivors from the electromyographic activity of 8 muscles during bilateral movements before and after 4 weeks of non-invasive BMI controlled robot therapy and physiotherapy. We computed the FSRI as well as features quantifying inter-limb structural differences and evaluated the correlation of these synergy-based measures with clinical scores.Main results. Correlation analysis revealed weak relationships between conventional features describing inter-limb synergy structural differences and motor function. In contrast, FSRI values during specific or combined movement data significantly correlated with UL motor function and recovery scores. Additionally, we observed that BMI-based training with contingent positive proprioceptive feedback led to improved FSRI values during the specific trained finger extension movement.Significance. We demonstrated that FSRI can be used as a reliable physiological biomarker of motor function and recovery in stroke, which can be targeted via BMI-based proprioceptive therapies and adjuvant physiotherapy to boost effective rehabilitation.

Lower Limb Movement Preparation in Chronic Stroke: A Pilot Study Toward an fNIRS-BCI for Gait Rehabilitation.

Background Thus far, most of the brain-computer interfaces (BCIs) developed for motor rehabilitation used electroencephalographic signals to drive prostheses that support upper limb movement. Only few BCIs used hemodynamic signals or were designed to control lower extremity prostheses. Recent technological developments indicate that functional near-infrared spectroscopy (fNIRS)-BCI can be exploited in rehabilitation of lower limb movement due to its great usability and reduced sensitivity to head motion artifacts. Objective The aim of this proof of concept study was to assess whether hemodynamic signals underlying lower limb motor preparation in stroke patients can be reliably measured and classified. Methods fNIRS data were acquired during preparation of left and right hip movement in 7 chronic stroke patients. Results Single-trial analysis indicated that specific hemodynamic changes associated with left and right hip movement preparation can be measured with fNIRS. Linear discriminant analysis classification of totHB signal changes in the premotor cortex and/or posterior parietal cortex indicated above chance accuracy in discriminating paretic from nonparetic movement preparation trials in most of the tested patients. Conclusion The results provide first evidence that fNIRS can detect brain activity associated with single-trial lower limb motor preparation in stroke patients. These findings encourage further investigation of fNIRS suitability for BCI applications in rehabilitation of patients with lower limb motor impairment after stroke.

Chronic stroke recovery after combined BCI training and physiotherapy: a case report.

A case of partial recovery after stroke and its associated brain reorganization in a chronic patient after combined brain computer interface (BCI) training and physiotherapy is presented. A multimodal neuroimaging approach based on fMRI and diffusion tensor imaging was used to investigate plasticity of the brain motor system in parallel with longitudinal clinical assessments. A convergent association between functional and structural data in the ipsilesional premotor areas was observed. As a proof of concept investigation, these results encourage further research on a specific role of BCI on brain plasticity and recovery after stroke.

Long-term effects of coordinative training in degenerative cerebellar disease.

Few clinical studies have evaluated physiotherapeutic interventions for patients with degenerative cerebellar disease. In particular, evidence for long-term effects and transfer to activities of daily life is rare. We have recently shown that coordinative training leads to short-term improvements in motor performance. To evaluate long-term benefits and translation to real world function, we here assessed motor performance and achievements in activities of daily life 1 year after a 4 week intensive coordinative training, which was followed by a home training program. Effects were assessed by clinical rating scales, a goal attainment score and quantitative movement analysis. Despite gradual decline of motor performance and gradual increase of ataxia symptoms due to progression of disease after 1 year, improvements in motor performance and achievements in activities of daily life persisted. Thus, also in patients with degenerative cerebellar disease, continuous coordinative training leads to long-term improvements, which translate to real world function.

Is there a role for benzodiazepines in the management of lumbar disc prolapse with acute sciatica?

Patients with acute lumbar disc prolapse with sciatica who are not considered candidates for surgery are usually treated with physiotherapy and non-steroidal anti-inflammatory agents. Moreover, the treatment with benzodiazepines is common practice in the absence of class I or II level of evidence. Here we assessed the role of benzodiazepines in the conservative management of acute lumbar disc prolapse. Using a placebo-controlled, double-blinded design, 60 patients were randomized to receive placebo or diazepam in addition to mechanical physiotherapy and analgesics for the first 7 days of conservative treatment of clinically and radiologically confirmed lumbar disc prolapse. The primary objective was to evaluate if physiotherapy plus analgesics, but without benzodiazepines, is equivalent to the same therapy plus benzodiazepines. The primary endpoint was centralization of referred pain at day 7. Twenty-six female and 34 male patients were enrolled. The median age was 42 years (range 22-68 years). Analysis of the primary endpoint demonstrated equivalence between placebo and diazepam (median 60% vs. 50% reduction of distance of referred pain at day 7) within the predefined equivalence tolerance of 20% at a significance level of p<0.05. Regarding the secondary endpoints, the median duration of the stay in hospital was shorter in the placebo arm (8 vs. 10 days, p=0.008), and the probability of pain reduction on a visual analog scale by more than 50% was twice as high in placebo patients (p<0.0015). Benzodiazepines should not be used routinely in patients treated with mechanical physiotherapy for lumbar disc prolapse.