Implantable motor neuroprostheses can restore functionality to individuals with neurological disabilities by electrically activating paralyzed muscles in coordinated patterns. The typical design of neuroprosthetic systems relies on a single multi-use device, but this limits the number of stimulus and sensor channels that can be practically implemented. To address this limitation, a modular neuroprosthesis, the “Networked Neuroprosthesis” (NNP), was developed. The NNP system is the first fully implanted modular neuroprosthesis that includes implantation of all power, signal processing, biopotential signal recording, and stimulating components. This paper describes the design of stimulation and recording modules, bench testing to verify stimulus outputs and appropriate filtering and recording, and validation that the components function properly while implemented in persons with spinal cord injury. The results of system testing demonstrated that the NNP was functional and capable of generating stimulus pulses and recording myoelectric, temperature, and accelerometer signals. Based on the successful design, manufacturing, and testing of the NNP System, multiple clinical applications are anticipated.

Background. Hemiparesis after stroke can severely limit an individual’s ability to perform activities of daily living. Functional electrical stimulation (FES) has the potential to generate functional arm and hand movements. We have observed that FES can produce functional hand opening when a stroke patient is relaxed, but the FES-produced hand opening is often overpowered by finger flexor coactivation in response to patient attempts to reach and open the hand. Objective. To determine if stimulating both reaching muscles and hand opening muscles makes it possible to achieve useful amounts of simultaneous reach and hand opening even in the presence of submaximal reaching effort. Methods. We measured reach and hand opening during a reach-then-open the hand task under different combinations of voluntary effort and FES for both reach and hand opening. Results. As effort was reduced and stimulation generated more movement, a greater amount of reach and hand opening was achieved. For the first time, this study quantified the effect of voluntary effort for reach and hand opening on stimulated hand opening. It also showed variability in the interaction of voluntary effort and stimulation between participants. Additionally, when participants were instructed to reach with partial effort during simultaneous FES, they achieved greater reach and hand opening. Conclusions. Simultaneous reaching and FES hand opening is improved by including FES for reach and reducing voluntary effort. In the future, an upper extremity neuroprosthesis that uses a combination of voluntary effort and FES assistance may enable users to perform activities of daily living.

Contralaterally controlled functional electrical stimulation (CCFES) is an innovative method of delivering neuromuscular electrical stimulation for rehabilitation of paretic limbs after stroke. It is being studied to evaluate its efficacy in improving recovery of arm and hand function and ankle dorsiflexion in chronic and subacute stroke patients. The initial studies provide preliminary evidence supporting the efficacy of CCFES.

Poststroke hemiparesis limits the ability to reach, in part due to involuntary muscle co-activation (synergies). Robotic approaches are being developed for both therapeutic benefit and continuous assistance during activities of daily living. Robotic assistance may enable participants to exert less effort, thereby reducing expression of the abnormal co-activation patterns, which could allow participants to reach further. This study evaluated how well participants could perform a reaching task with robotic assistance that was either provided independent of effort in the vertical direction or in the sagittal plane in proportion to voluntary effort estimated from electromyograms (EMG) on the affected side. Participants who could not reach targets without assistance were enabled to reach further with assistance. Constant anti-gravity force assistance that was independent of voluntary effort did not reduce the quality of reach and enabled participants to exert less effort while maintaining different target locations. Force assistance that was proportional to voluntary effort on the affected side enabled participants to exert less effort and could be controlled to successfully reach targets, but participants had increased difficulty maintaining a stable position. These results suggest that residual effort on the affected side can produce an effective command signal for poststroke assistive devices.

Objective The objective of this work was to quantify the effects of a fully implanted pulse generator to activate or augment actions of hip, knee, and ankle muscles after stroke. Design The subject was a 64-year-old man with left hemiparesis resulting from hemorrhagic stroke 21 months before participation. He received an 8-channel implanted pulse generator and intramuscular stimulating electrodes targeting unilateral hip, knee, and ankle muscles on the paretic side. After implantation, a stimulation pattern was customized to assist with hip, knee, and ankle movement during gait. The subject served as his own concurrent and longitudinal control with and without stimulation. Outcome measures included 10-m walk and 6-minute timed walk to assess gait speed, maximum walk time, and distance to measure endurance, and quantitative motion analysis to evaluate spatial-temporal characteristics. Assessments were repeated under 3 conditions: (1) volitional walking at baseline, (2) volitional walking after training, and (3) walking with stimulation after training. Results Volitional gait speed improved with training from 0.29 m/s to 0.35 m/s and further increased to 0.72 m/s with stimulation. Most spatial-temporal characteristics improved and represented more symmetrical and dynamic gait. Conclusions These data suggest that a multijoint approach to implanted neuroprostheses can provide clinically relevant improvements in gait after stroke. To Claim CME Credits: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME Objectives: Upon completion of this article, the reader should be able to do the following: (1) Describe the rationale for evaluating a multijoint implanted neuroprosthesis to improvewalkingafter stroke; (2)Understand the study design and conclusions that can be inferred as a result of the design; and (3) Discuss the statistical significance and clinical relevance of changes between (a) volitional walking at baseline, (b) volitional walking after training, and (c) walking with stimulation after training. Level: Advanced Accreditation: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The Association of Academic Physiatrists designates this activity for a maximum of 1.5 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Injury or disease often compromise walking dynamics and negatively impact quality of life and independence. Assessing methods to restore or improve pathological gait can be expedited by examining a global parameter that reflects overall musculoskeletal control. Center of mass (CoM) kinematics follow well-defined trajectories during unimpaired gait, and change predictably with various gait pathologies. We propose a method to estimate CoM trajectories from inertial measurement units (IMUs) using a bidirectional Long Short-Term Memory neural network to evaluate rehabilitation interventions and outcomes. Five non-disabled volunteers participated in a single session of various dynamic walking trials with IMUs mounted on various body segments. A neural network trained with data from four of the five volunteers through a leave-one-subject out cross validation estimated the CoM with average root mean square errors (RMSEs) of 1.44cm, 1.15cm, and 0.40cm in the mediolateral (ML), anteroposterior (AP), and inferior/superior (IS) directions respectively. The impact of number and location of IMUs on network prediction accuracy was determined via principal component analysis. Comparing across all configurations, three to five IMUs located on the legs and medial trunk were the most promising reduced sensor sets for achieving CoM estimates suitable for outcome assessment. Lastly, the networks were tested on data from an individual with hemiparesis with the greatest error increase in the ML direction, which could stem from asymmetric gait. These results provide a framework for assessing gait deviations after disease or injury and evaluating rehabilitation interventions intended to normalize gait pathologies.