William D. Memberg

An elbow extension neuroprosthesis for individuals with tetraplegia

Functional electrical stimulation (FES) of the triceps to restore control of elbow extension was integrated into a portable hand grasp neuroprosthesis for use by people with cervical level spinal cord injury. An accelerometer mounted on the upper arm activated triceps stimulation when the arm was raised above a predetermined threshold angle. Elbow posture was controlled by the subjects voluntarily flexing to counteract the stimulated elbow extension. The elbow moments created by the stimulated triceps were at least 4 N.m, which was sufficient to extend the arm against gravity. Electrical stimulation of the triceps increased the range of locations and orientations in the workspace over which subjects could grasp and move objects. In addition, object acquisition speed was increased. Thus elbow extension enhances a persons ability to grasp and manipulate objects in an unstructured environment.

A surgically-implanted intramuscular electrode for an implantable neuromuscular stimulation system

An intramuscular electrode has been developed for use with an implantable neuromuscular stimulator. In vitro tests indicate that the electrode will maintain a stable position within the muscle, but is capable of being removed intact. When tested in a buffered saline environment at the maximum stimulation parameters (0.4 /spl mu/C/mm/sup 2//phase), there was no corrosion of the stimulating surface. In vivo evaluations were conducted, in which four sets of 4 intramuscular electrodes and 4 epimysial electrodes, were surgically implanted in the forelimb of 4 dogs. Each set was connected to an implanted neuromuscular stimulator. All but 1 of the 16 intramuscular electrodes operated properly throughout the study, producing responses functionally indistinguishable from epimysial electrodes. One electrode fractured due to improper surgical placement. After removal, some pitting corrosion was observed in 2 of the 15 retrieved intramuscular electrodes, possibly due to minute surface defects resulting from the electrode manufacturing process. >

Restoration of reaching and grasping movements through brain-controlled muscle stimulation in a person with tetraplegia: a proof-of-concept demonstration

SUMMARY Background People with chronic tetraplegia due to high cervical spinal cord injury (SCI) can regain limb movements through coordinated electrical stimulation of peripheral muscles and nerves, known as Functional Electrical Stimulation (FES). Users typically command FES systems through other preserved, but limited and unrelated, volitional movements (e.g. facial muscle activity, head movements). We demonstrate an individual with traumatic high cervical SCI performing coordinated reaching and grasping movements using his own paralyzed arm and hand, reanimated through FES, and commanded using his own cortical signals through an intracortical brain-computer-interface (iBCI). Methods The study participant (53 years old, C4, ASIA A) received two intracortical microelectrode arrays in the hand area of motor cortex, and 36 percutaneous electrodes for electrically stimulating hand, elbow, and shoulder muscles. The participant used a motorized mobile arm support for gravitational assistance and to provide humeral ab/adduction under cortical control. We assessed the participant’s ability to cortically command his paralyzed arm to perform simple single-joint arm/hand movements and functionally meaningful multi-joint movements. We compared iBCI control of his paralyzed arm to that of a virtual 3D arm. This study is registered with ClinicalTrials.gov, NCT00912041. Findings The participant successfully cortically commanded single-joint and coordinated multi-joint arm movements for point-to-point target acquisitions (80% – 100% accuracy) using first a virtual arm, and second his own arm animated by FES. Using his paralyzed arm, the participant volitionally performed self-paced reaches to drink a mug of coffee (successfully completing 11 of 12 attempts within a single session) and feed himself. Interpretation This is the first demonstration of a combined FES+iBCI neuroprosthesis for both reaching and grasping for people with SCI resulting in chronic tetraplegia, and represents a major advance, with a clear translational path, for clinically viable neuroprostheses for restoring reaching and grasping post-paralysis.BACKGROUND People with chronic tetraplegia, due to high-cervical spinal cord injury, can regain limb movements through coordinated electrical stimulation of peripheral muscles and nerves, known as functional electrical stimulation (FES). Users typically command FES systems through other preserved, but unrelated and limited in number, volitional movements (eg, facial muscle activity, head movements, shoulder shrugs). We report the findings of an individual with traumatic high-cervical spinal cord injury who coordinated reaching and grasping movements using his own paralysed arm and hand, reanimated through implanted FES, and commanded using his own cortical signals through an intracortical brain-computer interface (iBCI). METHODS We recruited a participant into the BrainGate2 clinical trial, an ongoing study that obtains safety information regarding an intracortical neural interface device, and investigates the feasibility of people with tetraplegia controlling assistive devices using their cortical signals. Surgical procedures were performed at University Hospitals Cleveland Medical Center (Cleveland, OH, USA). Study procedures and data analyses were performed at Case Western Reserve University (Cleveland, OH, USA) and the US Department of Veterans Affairs, Louis Stokes Cleveland Veterans Affairs Medical Center (Cleveland, OH, USA). The study participant was a 53-year-old man with a spinal cord injury (cervical level 4, American Spinal Injury Association Impairment Scale category A). He received two intracortical microelectrode arrays in the hand area of his motor cortex, and 4 months and 9 months later received a total of 36 implanted percutaneous electrodes in his right upper and lower arm to electrically stimulate his hand, elbow, and shoulder muscles. The participant used a motorised mobile arm support for gravitational assistance and to provide humeral abduction and adduction under cortical control. We assessed the participants ability to cortically command his paralysed arm to perform simple single-joint arm and hand movements and functionally meaningful multi-joint movements. We compared iBCI control of his paralysed arm with that of a virtual three-dimensional arm. This study is registered with ClinicalTrials.gov, number NCT00912041. FINDINGS The intracortical implant occurred on Dec 1, 2014, and we are continuing to study the participant. The last session included in this report was Nov 7, 2016. The point-to-point target acquisition sessions began on Oct 8, 2015 (311 days after implant). The participant successfully cortically commanded single-joint and coordinated multi-joint arm movements for point-to-point target acquisitions (80-100% accuracy), using first a virtual arm and second his own arm animated by FES. Using his paralysed arm, the participant volitionally performed self-paced reaches to drink a mug of coffee (successfully completing 11 of 12 attempts within a single session 463 days after implant) and feed himself (717 days after implant). INTERPRETATION To our knowledge, this is the first report of a combined implanted FES+iBCI neuroprosthesis for restoring both reaching and grasping movements to people with chronic tetraplegia due to spinal cord injury, and represents a major advance, with a clear translational path, for clinically viable neuroprostheses for restoration of reaching and grasping after paralysis. FUNDING National Institutes of Health, Department of Veterans Affairs.

An analysis of the reliability of percutaneous intramuscular electrodes in upper extremity FNS applications

Electrical stimulation through chronically indwelling percutaneous intramuscular electrodes has been utilized to restore functional grasp in paralyzed individuals. A retrospective analysis of the reliability of the electrode has demonstrated the utility of these electrodes for chronic use in functional neuromuscular stimulation of the upper extremity. The study involved 710 electrodes implanted in 38 patients in Cleveland over a 13.5 year period. Complications were infrequent and minor. The probability of an electrode surviving for six months was 88%, allowing outpatient use of an upper extremity neuroprosthetic system. >

Implanted Neuroprosthesis for Restoring Arm and Hand Function in People With High Level Tetraplegia

OBJECTIVE To develop and apply an implanted neuroprosthesis to restore arm and hand function to individuals with high level tetraplegia. DESIGN Case study. SETTING Clinical research laboratory. PARTICIPANTS Individuals with spinal cord injuries (N=2) at or above the C4 motor level. INTERVENTIONS The individuals were each implanted with 2 stimulators (24 stimulation channels and 4 myoelectric recording channels total). Stimulating electrodes were placed in the shoulder and arm, being, to our knowledge, the first long-term application of spiral nerve cuff electrodes to activate a human limb. Myoelectric recording electrodes were placed in the head and neck areas. MAIN OUTCOME MEASURES Successful installation and operation of the neuroprosthesis and electrode performance, range of motion, grasp strength, joint moments, and performance in activities of daily living. RESULTS The neuroprosthesis system was successfully implanted in both individuals. Spiral nerve cuff electrodes were placed around upper extremity nerves and activated the intended muscles. In both individuals, the neuroprosthesis has functioned properly for at least 2.5 years postimplant. Hand, wrist, forearm, elbow, and shoulder movements were achieved. A mobile arm support was needed to support the mass of the arm during functional activities. One individual was able to perform several activities of daily living with some limitations as a result of spasticity. The second individual was able to partially complete 2 activities of daily living. CONCLUSIONS Functional electrical stimulation is a feasible intervention for restoring arm and hand functions to individuals with high tetraplegia. Forces and movements were generated at the hand, wrist, elbow, and shoulder that allowed the performance of activities of daily living, with some limitations requiring the use of a mobile arm support to assist the stimulated shoulder forces.

Restoration of elbow extension via functional electrical stimulation in individuals with tetraplegia.

Functional electrical stimulation of the triceps is a method of restoring elbow extension to individuals with paralyzed triceps. Eleven arms of individuals with cervical-level spinal cord injuries (SCIs) received a triceps electrode as an addition to a hand-grasp neuroprosthesis. Stimulation was controlled either as part of a preprogrammed pattern or via a switch or an accelerometer that was connected to the neuroprosthesis external controller. The outcome measures were (1) elbow extension moments at different elbow positions, (2) performance in controllable workspace experiments, and (3) comparison to an alternative method of providing elbow extension in these individuals--a posterior deltoid (PD) to triceps tendon transfer. Stimulated elbow extension moments in 11 arms ranged from 0.8 to 13.3 N.m. The stimulated elbow extension moments varied with elbow angle in a manner consistent with the length-tension properties of the triceps. Triceps stimulation provided a significantly stronger elbow extension moment than the PD to triceps tendon transfer. The elbow extension moment generated by the tendon transfer and triceps electrode being activated together was always greater than either method used separately. Stimulation of the long head of the triceps should be avoided in persons with weak shoulder abduction, since the long head adducts the shoulder and limits shoulder function in these cases. Statistically, elbow extension neuroprostheses significantly increased the ability to successfully reach and move an object and significantly decreased the time required to acquire an object while reaching.

Electrically stimulated elbow extension in persons with C5/C6 tetraplegia: A functional and physiological evaluation

OBJECTIVE To measure the effect of electrically stimulated triceps on elbow extension strength, range of motion, and the performance of overhead reaching tasks. SETTING Clinical research laboratory. PARTICIPANTS Four individuals with spinal cord injuries at the C5 or C6 motor level. INTERVENTIONS The participants, who already had an implanted upper extremity neuroprosthesis, were provided with elbow extension through functional electrical stimulation (FES) of the triceps brachii. MAIN OUTCOME MEASURES Comparisons of stimulated elbow extension to voluntary elbow extension: (1) evaluations of impairment such as range of motion and strength; (2) performance of a set of functional overhead reaching tasks that required elbow extension; (3) a usage survey (conducted by telephone) to examine use of triceps stimulation in the home and community. RESULTS All participants achieved greater range of motion and strength of elbow extension with stimulated triceps versus without. Overall functional task performance improved in 100% of the tasks tested for all but one participant, who showed improvement in 60% of the tasks. Participants reported using the triceps in at least one activity for at least 90% of the days the neuroprosthesis was donned.

A grasp force and position sensor for the quantitative evaluation of neuroprosthetic hand grasp systems

An instrumented grasp sensor has been developed for use in quantitative evaluation of neuroprosthetic hand grasps. This hand-held device monitors both grasp force and grasp opening with the subject utilizing either palmar or lateral prehension, and can be used to quantify the grasping of variable-sized or compliant objects. The grasp sensor provides a quantitative tool to analyze a subjects hand grasp, thus allowing the neuro-prosthetic system to be tuned for the best performance. It can supply data on how a grasp changes under various conditions, such as different wrist positions. The device can also be used to perform quantitative comparisons for future neuroprosthesis improvements, such as the addition of sensory feedback, closed-loop control systems, and alternative command/control methods. The simultaneous measurement of grasp opening and force could prove useful in applications other than a neuroprosthesis, such as quantifying other hand impairments and studying the physiological control of grasp. >

An Implanted Neuroprosthesis for High Tetraplegia

Individuals with high tetraplegia (ASIA classification C4 or higher) have few options to restore upper extremity function. One promising alternative for restoring function to paralyzed muscles is the use of functional electrical stimulation (FES). Initial FES applications for individuals with high tetraplegia have been limited. A major difficulty encountered in the application of FES in high tetraplegia has been the inability to achieve shoulder stabilization and mobilization primarily due to the denervation of key muscles. Another major difficulty has been the limited alternatives to provide control of the stimulated limb. As a result of these difficulties, the functional outcomes of these initial systems have been limited. Advances in technology and surgical techniques have been made that may provide methods for overcoming these limitations. Muscle denervation can be addressed through neurotization techniques to improve voluntary function and increase the response of paralyzed muscles to electrical stim...

Multi-Muscle FES Force Control of the Human Arm for Arbitrary Goals

We present a method for controlling a neuroprosthesis for a paralyzed human arm using functional electrical stimulation (FES) and characterize the errors of the controller. The subject has surgically implanted electrodes for stimulating muscles in her shoulder and arm. Using input/output data, a model mapping muscle stimulations to isometric endpoint forces measured at the subjects hand was identified. We inverted the model of this redundant and coupled multiple-input multiple-output system by minimizing muscle activations and used this inverse for feedforward control. The magnitude of the total root mean square error over a grid in the volume of achievable isometric endpoint force targets was 11% of the total range of achievable forces. Major sources of error were random error due to trial-to-trial variability and model bias due to nonstationary system properties. Because the muscles working collectively are the actuators of the skeletal system, the quantification of errors in force control guides designs of motion controllers for multi-joint, multi-muscle FES systems that can achieve arbitrary goals.