P.H. Peckham

Synthesis of hand grasp using functional neuromuscular stimulation

A functional neuromuscular stimulation system developed to provide grasp-release functions in quadriplegic individuals is discussed. A single command input from the subject controls the stimulus levels to a number of electrodes, thus simultaneously activating several muscles. A method for synthesizing the command input to stimulus output relationship has been developed. The first step involves electrode profiling, which is a method for characterizing the output of an individual electrode/muscle combination. The electrodes are then grouped according to function, and a set of rule-based procedures is used to synthesize the basic grasp parameters. Results demonstrating the output from lateral and palmar grasps developed by this method are presented. The method has successfully resulted in grasping patterns that can be utilized functionally. Limitations of the method and future improvements are discussed.<<ETX>>

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. >

A flexible, portable system for neuromuscular stimulation in the paralyzed upper extremity

A portable functional neuromuscular stimulation (FNS) system for control of the muscles of the paralyzed upper extremity has been developed and evaluated for outpatient use. The system, which has been tested over a five-year period, incorporates an 8-bit CMOS microprocessor which can be programmed to accept and process a variety of user-generated commands and to output complex stimulus patterns. Eight channels of analog input can be used to control four channels of constant-current-compensation monophasic stimulus output. The portable FNS system is programmed using a multichannel laboratory stimulation system.<<ETX>>

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. >

Electrode characterization for functional application to upper extremity FNS

A quantitative method has been developed to characterize the isometric vectors of electrically simulated paralyzed muscles of the thumb. The vectorial force output as a function of the stimulus level was measured for individual electrode/muscle combinations in a number of intramuscular and epimysial electrodes implanted in paralyzed thenar of cervical-level spinal-cord-injury subjects. Vectors were used to determine the output characteristics of each electrode/muscle combination. The characteristics studied included the strength of the contraction, the stimulus level at which fibers from other muscles are stimulated, the recruitment gain of force, dependency of the output on the skeletal position, and the direction of force produced.<<ETX>>

In-line lead connector for use with implanted neuroprosthesis

The design, implementation, and preliminary testing of an implantable in-line connector for individual lead-wires is presented. The connector provides for replacement of implanted components without disturbing other elements of the implanted system. Its flexibility and size makes it suitable for implantation in neuromuscular applications.<<ETX>>

The monitoring of tendon tension with an implantable intratendon probe and its use in the control of neuroprostheses

The use of a probe measuring tendon tension for the purpose of controlling a neuroprosthesis suited to spinal cord injured persons is investigated. The implanted probe detected inwardly directed radial force exerted by the tendon as the result of longitudinal tension. Varying types of load were applied to the tendon in order to measure static and dynamic parameters of the probe within the tendon. The results are discussed with respect to the potential use of the probe, within an active muscles tendon, as a hand grasp neuroprosthesis controller. In addition, use of the probe to monitor electrically stimulated paralyzed muscle for the augmentation of closed loop control schemes is discussed.

Challenges and Opportunities in Restoring Function After Paralysis

Neurotechnology has made major advances in development of interfaces to the nervous system that restore function in paralytic disorders. These advances enable both restoration of voluntary function and activation of paralyzed muscles to reanimate movement. The technologies used in each case are different, with external surface stimulation or percutaneous stimulation generally used for restoration of voluntary function, and implanted stimulators generally used for neuroprosthetic restoration. The opportunity to restore function through neuroplasticity has demonstrated significant advances in cases where there are retained neural circuits after the injury, such as spinal cord injury and stroke. In cases where there is a complete loss of voluntary neural control, neural prostheses have demonstrated the capacity to restore movement, control of the bladder and bowel, and respiration and cough. The focus of most clinical studies has been primarily toward activation of paralyzed nerves, but advances in inhibition of neural activity provide additional means of addressing the paralytic complications of pain and spasticity, and these techniques are now reaching the clinic. Future clinical advances necessitate having a better understanding of the underlying mechanisms, and having more precise neural interfaces that will ultimately allow individual nerve fibers or groups of nerve fibers to be controlled with specificity and reliability. While electrical currents have been the primary means of interfacing to the nervous system to date, optical and magnetic techniques under development are beginning to reach the clinic, and provide great opportunity. Ultimately, techniques that combine approaches are likely to be the most effective means for restoring function, for example combining regeneration and neural plasticity to maximize voluntary activity, combined with neural prostheses to augment the voluntary activity to functional levels of performance. It is a substantial challenge to bring any of these techniques through clinical trials, but as each of the individual techniques is sufficiently developed to reach the clinic, these present great opportunities for enabling patients with paralytic disorders to achieve substantial independence and restore their quality of life.

COORDINATED TWO MODE GRASP IN THE QUADRIPLEGIC INITIATED BY FUNCTIONAL NEUROMUSCULAR STIMULATION.

Electrical stimulation of selected paralyzed forearm and hand muscles in C5 and C6 spinal cord injury patients provides control of two types of functional hand movement. Chronically indwelling percutaneous coiled wire electrodes were used to stimulate the muscles. Control of the muscles is open loop, using coordination algorithms tailored to each individual subject. Personal stimulation devices have been provided to the patients to enable them to obtain functional use of their paralyzed extremity.

Development of an implantable networked neuroprosthesis

Neuroprosthetic devices are powerful tools providing functional enhancement for individuals with central nervous system disorders, such as spinal cord injury and stroke. Life sustaining and enhancing independent functions such as breathing, standing, walking, grasping, reaching, micturition, and defecation have all been clinically demonstrated using neuroprostheses. Existing implanted neuroprosthetic systems utilize considerable external powering and signal processing, and each system must be customized to the specific application for which it is intended, severely limiting progress in the field and delaying the introduction of new technology to the end user. The networked neuroprosthetic system (NNPS) is based on a network of small implanted modules, distributed throughout the body, and linked to a centralized power source. The modules are connected through a network cable that distributes power to each module from a central rechargeable lithium-ion battery. Each module contains processing capabilities, communicates with other modules via the network cable, and is reprogrammable over the network using a central wireless transcutaneous link. The NNPS is extremely flexible and can be scaled to meet the technical needs of a broad range of neuroprosthetic applications through the selection of the appropriate modules providing the means for broader clinical application of neuroprostheses